MCRP 3-40.3B 

(Formerly MCRP 6-22C) 

Radio Operator's 

Handbook

U.S. Marine Corps

PCN 144 00067 00 

DISTRIBUTION STATEMENT A: approved for public release; distribution is unlimited
MCCDC (C 42)

10 Jul 2001

ERRATUM

to

MCRP 3-40.38

RADIO OPERATOR'S HANDBOOK

1. For administrative purposes, the publication short title

has been reidentified. Change MCRP 6-22C" to read:

"MCRP 3-40.3B" of June 1999 wherever it appears in the Manual.

PCN 144 000067 80
DEPARTMENT OF THE NAVY

Headquarters United States Marine Corps

Washington, D.C. 20380-1775

2 June 1999

FOREWORD

Marine Corps Warfighting Publication (MCWP) 6-22, Communications

and Information Systems, provides the doctrine and tactics, techniques,

and procedures for the conduct of communications and information systems across the spectrum of Marine air-ground task force (MAGTF)

operations. Marine Corps Reference Publication (MCRP) 3-40.3B, Radio

Operator’s Handbook, complements and expands upon this information

by detailing doctrine, tactics, techniques, and procedures for operating

single-channel high frequency (HF), very high frequency (VHF), and

ultrahigh frequency (UHF) radios. The primary target audience for this

publication is Marine Corps radio operators and other users of singlechannel radios.

MCRP 3-40.3B describes—

l Basic radio principles.

l Single-channel radio.

l Equipment sighting and grounding techniques.

l Antennas.

l Interference.

l Radio operations under unusual conditions.

l Electronic warfare. 

MCRP 3-40.3B provides the requisite information needed by Marine radio

operators to understand, plan, and execute successful single-channel

radio operations in support of the MAGTF.
MCWP 3-40.3B supersedes FMFM 3-35, Radio Operator’s

Handbook, dated 26 September 1991.

Reviewed and approved this date.

BY DIRECTION OF THE COMMANDANT OF THE MARINE CORPS

J. E. RHODES

Lieutenant General, U.S. Marine Corps

Commanding General

Marine Corps Combat Development Command

DISTRIBUTION: 144 000067 00
Radio Operator’s Handbook

Table of Contents

Chapter 1. Radio Principles

Section I. Theory and Propagation

Basic Components of Radio Equipment 

Radio Waves 

Radio Wave Propagation 

Section II. Modulation and Single Side Band 

Transmission

Modulation 

Single Side Band Transmission 

Chapter 2. Single-Channel Radio

Single-Channel Radio Communications Equipment 

High Frequency Radio 

Very High Frequency Radio 

Ultrahigh Frequency Radio 

Data Communications 

Chapter 3. Equipment Siting and Grounding Techniq

High Frequency 

Very High Frequency and Ultrahigh Frequency 

Grounding Techniques 

Data Communications 

Chapter 4. Antennas

High Frequency Antennas 

Very High Frequency Antennas 

Antenna Length 
Chapter 5. Interference

Natural Interference 

Manmade Interference 

Poor Equipment Condition and Improper Usage 

Frequency Interference and Intermodulation 

Use of Unauthorized Frequencies 

Frequency Reuse 

Chapter 6. Radio Operations Under Unusual Condition

Operations in Desert Areas 

Operations in Jungle Areas 

Operations in a Cold Weather Environment 

Operations in Mountainous Areas 

Operations in Special Environments 

Chapter 7. Electronic Warfare

Electronic Attack Techniques 

Electronic Protection Techniques 

Electronic Warfare Support Techniques 

Appendices

A Map Coordinates 

B Time Zones 

C Prowords 

D Phonetic Alphabet 

E Phonetic Numerals 

F Prosigns 

G Instructions for Preparing Field Messages 

H Radio Log 

I Metric System Conversion Table 

J Authentication 

K International Morse Code 

L Frequency Prediction Means 

M Position and Navigation Systems 

N Size of Dipole and Inverted L Antennas 

O Field Repair and Expedients 

P Radio Operator’s Checklist 

Q Glossary 

R References and Related Publications 
Chapter 1

Radio Principles

Communications and information systems (CIS) are any systems whose

primary functions are to collect, process, or exchange information. The

fundamental requirement is to provide the Marine air-ground task force

(MAGTF) commander with a reliable, secure, fast, and flexible communications network. 

Communications and information systems automate routine functions,

thereby freeing commanders and staffs to focus on those aspects of command and control that require experience, judgment, and intuition. 

These systems and the personnel who install, operate, and maintain them

play a key role in the command and control of the MAGTF. Communications and informations systems support the commander and every staff

section in every phase of operations planning and execution. 

These systems facilitate information flow throughout the MAGTF and

provide shared situational awareness, informed decisionmaking, and

rapid dissemination of decisions. 

The success of the MAGTF in the modern battlespace depends on the

effective employment of communications and information systems.

Single-channel radio (SCR) is one of the most important components of

MAGTF CIS.
1-2 _______________________________________________ MCRP 3-40.3B

Section I. Theory and Propagation

BASIC COMPONENTS OF RADIO EQUIPMENT

The radio equipment for communication between two stations and the

path the signal follows through the air is called a radio link. A radio link

consists of seven components: the transmitter, power supply, transmission lines, transmitting antenna, propagation path, receiving antenna,

and receiver (see figure 1-1).

The transmitter generates a radio signal. The power supply (i.e., battery

or generator) supplies power for the operating voltage of the radio. The

transmission line delivers the signal from the transmitter to the antenna.

TRANSMISSION

LINES

TRANSMITTING 

 ANTENNA

PROPAGATION

PATH

 RECEIVING 

 ANTENNA

POWER

SUPPLY

TRANSMITTER RECEIVER

Figure 1-1. Radio Link.
Radio Operator’s Handbook ______________________________ 1-3

The transmitting antenna sends the radio signal into space toward the

receiving antenna. The path in space that the radio signal follows as it

goes to the receiving antenna is the propagation path. The receiving

antenna intercepts or receives the signal and sends it through a transmission line to the receiver. The receiver processes the radio signal so the

human ear can hear it.

When transmitting, the radio operator aims to provide the strongest possible signal at the site of the receiving station. The best possible signal is

that signal which will provide the greatest signal-to-noise ratio at the

receiving antenna. 

To transmit the best possible signal, select or determine the—

l Optimum frequency. 

l Best antenna for that frequency based on the available space of the

transmitting site.

l Proper propagation path.

RADIO WAVES 

Propagation Velocity (Speed) 

Radio waves travel near the surface of the Earth and radiate skyward at

various angles to the Earth’s surface. These electromagnetic waves

travel through space at the speed of light, approximately 300,000 kilometers (km) or 186,000 miles (mi) per second. 

Wavelength 

Wavelength is the distance between the crest of one wave and the crest

of the next wave (see figure 1-2 on page 1-4). It can also be the length of

one complete cycle of the waveform. It is also the distance traveled during one complete cycle. The length of the wave is always measured in

meters. 
1-4 _______________________________________________ MCRP 3-40.3B

Radio Frequency 

The frequency of a radio wave is the number of complete cycles that

occur in one second. The longer the cycle, the longer the wavelength and

the lower the frequency. The shorter the cycle, the shorter the wavelength and the higher the frequency. Frequency is measured and stated in

units called hertz (Hz). One cycle per second is stated as 1 hertz.

Because the frequency of a radio wave is very high, it is generally measured and stated in thousands of hertz (kilohertz [KHz]) or in millions of

hertz (megahertz [MHz]). One KHz is equal to 1,000 cycles per second,

and 1 MHz is equal to a million cycles per second. Sometimes frequencies are expressed in billions of hertz (gigahertz [GHz]). One GHz is

equal to a billion cycles per second. 

For practical purposes, the velocity of a radio wave is considered to be

constant, regardless of the frequency or the amplitude of the transmitted

wave. Therefore, to find the frequency when the wavelength is known,

divide the velocity by the wavelength. 

To find the wavelength when the frequency is known, divide the velocity

by the frequency. 

Frequency (hertz)

=

300 million (meters per second)

Wavelength (meters)

Wavelength (meters)

=

300 million (meters per second)

Frequency (hertz)

STRENGTH

TIME OR DISTANCE

ONE CYCLE

WAVELENGTH

PEAK

PEAK

0

Figure 1-2. Radio Waves.
Radio Operator’s Handbook ______________________________ 1-5

Within the radio frequency spectrum (see figure 1-3), radio frequencies

are divided into groups or bands of frequencies. The radio frequency

spectrum is part of the electromagnetic spectrum. Most tactical radio sets

operate within a 2- to 400-MHz range within the frequency spectrum. 

Each frequency band has certain characteristics. The ranges and power

requirements shown in table 1-1 are for normal operating conditions

(proper siting and antenna orientation and correct operating procedures).

The ranges will change according to the condition of the propagation

medium and the transmitter output power. 

Table 1-1. Frequency Range Characteristics.

Band Ground Wave

Range

Sky Wave 

Range

Power 

Required

HF 0-50 miles 100-8000 miles .5-5 kW

VHF 0-30 miles 50-150 miles .5 or less 

kW

UHF 0-50 miles N/A .5 or less 

kW

Figure 1-3. Electromagnetic Spectrum.

VISIB

L

E

UV X-RAY GAMMARAY

COSMICRAY

3 MHz30 MHz300

MHz

3GHz

H

F

VH

F

U

H

F

IR

RADIO
1-6 _______________________________________________ MCRP 3-40.3B

RADIO WAVE PROPAGATION 

There are two principal paths by which radio waves travel from a transmitter to the receiver (See figure 1-4): ground wave—which travels

directly from the transmitter to the receiver and sky wave—which travels up to the ionosphere and is refracted (i.e., bent downward) back to

the Earth. Short-distance, ultrahigh frequency (UHF), and upper very

high frequency (VHF) transmissions are by ground waves. Long-distance, high frequency (HF) transmission is principally by sky waves.

Single-channel radio sets can use ground wave or sky wave propagation

for communications. 

Ground Wave Propagation 

Radio communications which use ground wave propagation do not use

or depend on waves that are refracted from the ionosphere (i.e., sky

waves). Ground wave propagation is affected by the electrical characteristics of the Earth and by the amount of diffraction (i.e., bending) of the

GROUND WAVES

IONOSPHERE

SKY WAVES

Figure 1-4. Principle Paths of Radio Waves.
Radio Operator’s Handbook ______________________________ 1-7

waves along the curvature of the Earth. The strength of the ground wave

at the receiver depends on the power output and frequency of the transmitter, the shape and conductivity of Earth along the transmission path,

and the local weather. The following paragraphs describe the components of a ground wave. See figure 1-5. 

Direct Wave. The direct wave is that part of the radio wave which travels

directly from the transmitting antenna to the receiving antenna. This part

of the wave is limited to the line of sight (LOS) distance between the

transmitting and receiving antennas, plus the small distance added by

atmospheric refraction and diffraction of the wave around the curvature

of the Earth. This distance can be extended by increasing the height of

the transmitting antenna, the receiving antenna, or both. 

Ground Reflected Wave. The ground reflected wave is that portion of the

radio wave which reaches the receiving antenna after being reflected

from the surface of the earth. Cancellation of the radio signal can occur

when the ground reflected component and the direct wave component

arrive at the receiving antenna at the same time and are 180° out of phase

with each other.

Surface Wave. The surface wave, which follows the curvature of the

Earth, is that part of the ground wave which is affected by the conductivity and dielectric constant of the Earth. 

GROUND REFLECTED

DIRECT WAVE

SURFACE

 WAVE

 WAVE

Figure 1-5. Ground Wave Propagation.
1-8 _______________________________________________ MCRP 3-40.3B

Sky Wave Propagation 

Radio communications that use sky wave propagation depend on the

ionosphere to provide the signal path between the transmitting and

receiving antennas. 

Ionospheric Structure. The ionosphere has four layers (see fig. 1-6). In

order of increasing heights and decreasing molecular densities, these

layers are labeled D, E, F1, and F2. During the day, when the rays of the

F1 & F2

F1 

E 

D 

F2 COMBINE

F2 250-500 km (250-420 km at night)

F1 200-250 km

E 90-130 km

D 75-90 km

SUN

AT NIGHT

F2

F1

E

D

DAYLIGHT POSITIONS

Figure 1-6. Layers of the Ionosphere.
Radio Operator’s Handbook ______________________________ 1-9

Sun are directed toward that portion of the atmosphere, all four layers

may be present. At night, the F1 and F2 layers seem to merge into a single F layer, and the D and E layers fade out. The actual number of layers,

their height above the Earth, and their relative intensity of ionization varies constantly. The following are layers of the ionosphere:

l D—exists only during daylight hours and has little effect in bending

the paths of high frequency radio waves. The main effect of the D

layer is to attenuate high frequency waves when the transmission path

is in sunlit regions. 

l E—used during the day for high frequency radio transmission over

intermediate distances (less than 2,400 km [1,500 mi]). At night, the

intensity of the E layer decreases, and it becomes useless for radio

transmission. 

l F—exists at heights up to 380 kilometers (240 mi) above the Earth

and is ionized all the time. It has two well-defined layers (F1 and F2)

during the day, and one layer (i.e., F) during the night. At night, the F

layer remains at a height of about 260 kilometers (170 mi) and is useful for long-range radio communications (over 2,400 km [1,500 mi]).

The F2 layer is the most useful of all layers for long-range radio communications, even though its degree of ionization varies appreciably

from day to day.

Factors Affecting the Ionosphere. The movements of the Earth around

the Sun and changes in the Sun’s activity contribute to ionospheric variations. There are two main classes of variations: regular, which is predictable; and irregular, which occurs from abnormal behavior of the Sun.

Regular Variations of the Ionosphere. The regular variations are— 

l Daily—caused by the rotation of the Earth.

l Seasonal—caused by the north and south progression of the Sun.

l 27-day—caused by the rotation of the Sun on its axis.

l 11-year—caused by the sunspot activity cycle going from maximum

to minimum, back to maximum levels of intensity. 
1-10 ______________________________________________ MCRP 3-40.3B

Irregular Variations of the Ionosphere. The current status of the four regular variations must be anticipated when planning a communications

system. There are also unpredictable, irregular variations that must be

considered. They have a degrading effect (at times blocking communications) which cannot be controlled or compensated for at present. Some

irregular variations are— 

l Sporadic E. When it is excessively ionized, the E layer often blocks

out the reflections back from the higher layers. It can also cause unexpected propagation of signals hundreds of miles beyond the normal

range. This effect can occur at any time.

l Sudden ionospheric disturbance (SID). A sudden ionospheric disturbance coincides with a bright solar eruption and causes abnormal ionization of the D layer. This effect causes total absorption of all

frequencies above approximately 1 MHz. It can occur without warning during daylight hours and last from a few minutes to several

hours. When SID occurs, receivers seem to go dead.

l Ionospheric storms. During these storms, sky wave reception above

approximately 1.5 MHz shows low intensity and is subject to a type

of rapid blasting and fading called “flutter fading.” These storms may

last from several hours to days and usually extend over the entire

Earth. 

Sunspots. Sunspots generate bursts of radiation that cause high levels of

ionization. The more sunspots, the greater the ionization. During periods

of low sunspot activity, frequencies above 20 MHz tend to be unusable

because the E and F layers are too weakly ionized to reflect signals back

to earth. At the peak of the sunspot cycle, however, it is not unusual to

have worldwide propagation on frequencies above 30 MHz.

Frequency Characteristics in the Ionosphere. The range of long-distance

radio transmission is determined primarily by the ionization density of

each layer. The higher the frequency, the greater the ionization density

required to reflect radio waves back to Earth. The upper (i.e., E and F)

layers reflect the higher frequencies because they are the most highly

ionized. The D layer, which is the least ionized, does not reflect frequencies above approximately 500 KHz. Thus, at any given time and for each
Radio Operator’s Handbook _____________________________ 1-11

ionized layer, there is an upper frequency limit at which radio waves sent

vertically upward are reflected back to Earth. This limit is called the critical frequency.

Radio waves directed vertically at frequencies higher than the critical

frequency pass through the ionized layer out into space. All radio waves

directed vertically into the ionosphere at frequencies lower than the critical frequency are reflected back to Earth. Radio waves used in communications are generally directed towards the ionosphere at some oblique

angle, called the angle of incidence. Radio waves at frequencies above

the critical frequency will be reflected back to Earth if transmitted at

angles of incidence smaller than a certain angle, called the critical angle.

At the critical angle and all angles larger than the critical angle the radio

waves will pass through the ionosphere if the frequency is higher than

the critical frequency. When the angle of transmission becomes smaller,

the radio waves will be reflected back to Earth. 

Transmission Paths. The distance from the transmitting antenna to the

place where the sky waves first return to Earth is called the skip distance.

The skip distance is dependent on the angle of incidence, the operating

frequency, and the height and density of the ionosphere. The antenna

height, in relation to the operating frequency, affects the angle that transmitted radio waves strike and penetrate the ionosphere and then return to

Earth. This angle of incidence can be controlled to obtain the desired

area of coverage. Lowering the antenna will increase the angle of transmission and provide broad and even signal patterns in a large area. The

use of near-vertical transmission paths is known as near-vertical incidence sky wave (NVIS). Raising the antenna will lower the angle of

incidence. Lowering the angle of incidence can produce a skip zone in

which no usable signal can be received. This area is bounded by the

outer edge of usable ground wave propagation and the point nearest the

antenna at which the sky wave returns to Earth. In most communications

situations, the skip zone is not a desirable condition. However, low

angles of incidence make long-distance communications possible. 

When a transmitted wave is reflected back to the surface of the Earth,

part of its energy is absorbed by the Earth. The remainder of its energy is

reflected back into the ionosphere to be reflected back again. This means
1-12 ______________________________________________ MCRP 3-40.3B

of transmission—by alternately reflecting the radio wave between the

ionosphere and the Earth—is called hops, and it enables radio waves to

be received at great distances from the point of origin. 

Maximum Usable and Lowest Usable Frequencies. There is a maximum

frequency at which a radio wave will return to Earth at a given distance

when a given ionized layer and a transmitting antenna with a fixed angle

of radiation is used. This frequency is called the maximum usable frequency (MUF). It is the monthly median of the daily highest frequency

that is predicted for sky wave transmission over a particular path at a

particular hour of the day. The MUF is always higher than the critical

frequency because the angle of incidence is less than 90°. If the distance

between the transmitter and the receiver is increased, the maximum

usable frequency will also increase. Radio waves lose some of their

energy through absorption by the D layer and the portion of the E layer

of the ionosphere at certain transmission frequencies.

The total absorption is less and communications are more satisfactory as

higher frequencies are used up to the level of the MUF. The absorption

rate is greatest for frequencies ranging from approximately 500 KHz to 2

MHz during the day. At night, the absorption rate decreases for all frequencies. As the frequency of transmission over any sky wave path is

decreased from high to low frequencies, a frequency will be reached at

which the received signal just overrides the level of atmospheric and

other radio noise interference. This is called the lowest useful frequency

(LUF) because frequencies lower than the LUF are too weak for useful

communications. The LUF also depends on the power output of the

transmitter as well as the transmission distance. When the LUF is greater

than the MUF, no sky wave transmission is possible.
Radio Operator’s Handbook _____________________________ 1-13

Section II. Modulation and Single Side Band 

Transmission

Radio communications equipment is used primarily to transmit voice

and data. Although sound can be converted to audio frequency electrical

energy, it is not practical to transmit it in this energy form through the

Earth’s atmosphere by electromagnetic radiation. For example, efficient

transmission of a 20-hertz audio signal would require an antenna almost

8,000 kilometers (5,000 mi) long. This would not apply when radio frequency electrical energy is used to carry the intelligence. When radio

frequency electrical energy is used, great distances can be covered; efficient antennas for radio frequencies are of practical lengths; and antenna

power losses are at reasonable levels. 

The frequency of the radio wave affects its propagation characteristics.

In the low frequency band (.03 to.3 MHz), the ground wave is very useful for communications over great distances. The ground wave signals

are quite stable and show little seasonal variation. In the medium frequency band (.3 to 3.0 MHz), the range of the ground wave varies from

about 24 kilometers (15 mi) at 3 MHz, to about 640 kilometers (400 mi)

at the lowest frequencies of this band. Sky wave reception is possible

during the day or night at any of the lower frequencies in this band. At

night, the sky wave is receivable at distances up to 12,870 kilometers

(8,000 mi). In the high frequency band (3 to 30 MHz), the range of the

ground wave decreases as frequency increases, and the sky waves are

greatly influenced by ionospheric considerations. 

In the very high frequency band (30 to 300 MHz), there is no usable

ground wave and only slight refraction of sky waves by the ionosphere

at the lower frequencies. The direct wave provides communications if

the transmitting and receiving antennas are elevated high enough above

the surface of the Earth. 

In the ultrahigh frequency band (300 to 3,000 MHz), the direct wave

must be used for all transmissions. Communications are limited to a

short distance beyond the horizon. Lack of static and fading in these

bands makes line of sight reception very satisfactory. Antennas that are

highly directional can be used to concentrate the beam of radio frequency (RF) energy, thus, increasing the signal intensity. 
1-14 ______________________________________________ MCRP 3-40.3B

MODULATION

Both amplitude modulation (AM) and frequency modulation (FM) transmitters produce RF carriers. The carrier is a wave of constant amplitude,

frequency, and phase which can be modulated by changing its amplitude, frequency, or phase. Thus, the RF carrier “carries” intelligence by

being modulated. Modulation is the process of superimposing intelligence (voice or coded signals) on the carrier. 

Amplitude Modulation 

Amplitude modulation is the variation of the RF power output of a transmitter at an audio rate. In other words, the RF energy increases and

decreases in power according to the audio frequencies superimposed on

the carrier signal. 

When audio frequency signals are superimposed on the radio frequency

carrier signal, additional RF signals are generated. These additional frequencies are equal to the sum of, and the difference between the audio

frequencies and the radio frequency used. For example, assume a 500-

KHz carrier is modulated by a 1-KHz audio tone. Two new frequencies

are developed, one at 501 KHz (the sum of 500 KHz and 1 KHz) and the

other at 499 KHz (the difference between 500 KHz and 1 KHz). If a

complex audio signal is used instead of a single tone, two new frequencies will be set up for each of the audio frequencies involved. The new

frequencies resulting from superimposing an audio frequency (AF) signal on an RF signal are called side bands. 

When the RF carrier is modulated by complex tones such as speech,

each separate frequency component of the modulating signal produces

its own upper and lower side band frequencies. The side band that contains the sum of the RF and AF signals is called the upper side band. The

side band that contains the difference between the RF and AF signals is

called the lower side band. 

The space occupied by a carrier and its associated side bands in

the radio frequency spectrum is called a channel. In amplitude modulation, the width of the channel (bandwidth) is equal to twice the highest
Radio Operator’s Handbook _____________________________ 1-15

modulating frequency. For example, if a 5,000 KHz (5 MHz) carrier is

modulated by a band of frequencies ranging from 200 to 5,000 cycles (.2

to 5 KHz), the upper side band extends from 5,000.2 to 5,005 KHz. The

lower side band extends from 4,999.8 KHz to 4,995 KHz. Thus, the

bandwidth is the difference between 5,005 KHz and 4,995 KHz, a total

of 10 KHz. 

Frequency Modulation 

Frequency modulation is the process of varying the frequency (rather

than the amplitude) of the carrier signal in accordance with the variations of the modulating signals. The amplitude or power of the FM carrier does not vary during modulation.

The frequency of the carrier signal when it is not modulated is called the

center or rest frequency. When a modulating signal is applied to the

carrier, the carrier signal will move up and down in frequency, away

from the center or rest frequency. 

The amplitude of the modulating signal determines how far away from

the center frequency the carrier will move. This movement of the carrier

is called deviation; how far the carrier moves is called the amount of

deviation. During reception of the FM signal, the amount of deviation

determines the loudness or volume of the signal. 

The FM signal leaving the transmitting antenna is constant in amplitude

but varies in frequency according to the audio signal. As the signal travels to the receiving antenna, it picks up natural and man-made electrical

noises that cause amplitude variations in the signal. All of these undesirable amplitude variations are amplified as the signal passes through successive stages of the receiver until the signal reaches a part of the

receiver called the limiter. The limiter is unique to FM receivers as is the

discriminator. 

The limiter eliminates the amplitude variations in the signal, then passes

it on to the discriminator which is sensitive to variations in the frequency

of the RF wave. The resultant constant amplitude, frequency-modulated

signal is then processed by the discriminator circuit which changes the
1-16 ______________________________________________ MCRP 3-40.3B

frequency variations into corresponding voltage amplitude variations.

These voltage variations reproduce the original modulating signal in a

headset, loudspeaker, or teletypewriter. Frequency modulation is generally used by radiotelephone transmitters operating in the VHF and

higher frequency bands. 

SINGLE SIDE BAND TRANSMISSION 

The intelligence of an AM signal is contained solely in the side bands.

Each side band contains all the intelligence needed for communications.

Therefore, one side band and the carrier signal can be eliminated. This is

the principle on which single side band (SSB) communications is based.

Although both side bands are generated within the modulation circuitry

of the SSB radio set, the carrier and one side band are removed before

any signal is transmitted.

The side band that is higher in frequency than the carrier is called the

upper side band (USB). The side band that is lower in frequency than the

carrier is called the lower side band (LSB). Either side band can be used

for communications as long as both the transmitter and the receiver are

adjusted to the same side band. Most SSB equipment operates in the

USB mode. The transmission of only one side band leaves open that portion of the RF spectrum normally occupied by the other side band of an

AM signal. This allows more emitters to be used within a given frequency range.

Single side band transmission is used in applications when it is desired

to— 

l Obtain greater reliability. 

l Limit size and weight of equipment. 

l Increase effective output without increasing antenna voltage. 

l Operate a large number of radio sets without heterodyne interference

(e.g., whistles and squeals) from radio frequency carriers. 

l Operate over long ranges without loss of intelligibility because of

selective fading.
Chapter 2

Single-Channel Radio 

SINGLE-CHANNEL RADIO COMMUNICATIONS 

EQUIPMENT 

Single-channel radio is the principal means of communications support

for MAGTF maneuver units. SCR communications equipment is easy to

operate. The networks are easily established, rapidly reconfigured, and,

most importantly, easily maintained on the move. SCR provides secure

voice communications and supports limited data information exchange.

SCR in the VHF and UHF bands is normally limited to line of sight. In

the HF band, SCR can support long-range communications. SCR satellite communications (SATCOM) provides mobility, flexibility, and ease

of operation with unlimited range. Limitations of SCR include susceptibility to enemy electronic warfare (i.e., cosite, terrain, and atmospheric

interference); the requirement for close coordination and detailed planning (i.e., a need for common timing, frequency, and equipment); and

limited spectrum availability. The latter is particularly critical in the case

of SATCOM.

MAGTF SCR equipment is fielded in many configurations and includes

hand-held, manpack, vehicle-mounted, bench-mounted, and sheltered

radios. These radios operate in simplex and half-duplex modes. The

most widely employed tactical radios provide integrated communications security (COMSEC) and jam resistance through frequency hopping. Tactical SCRs operate in the three military radio frequency bands

shown in Table 2-1 on page 1-2. 
2-2 _______________________________________________ MCRP 3-40.3B

HIGH FREQUENCY RADIO

HF radio equipment is capable of both long- and short-range secure

voice and data communications. Data communications capability is typically limited to rates of 2.4 kilobits per second (kbps). Data transmission

requires modems specifically designed for operation in this band of the

radio spectrum. The AN/PRC-104 is capable of remote operation by

using the analog AN/GRA-39B radio remote control. See fig. 2-1.

Table 2-1. SCR Equipment.

Frequency 

Band

MAGTF SCR

Equipment Used

Operating 

Frequency 

Range

Typical 

Application

HF AN/PRC-104

AN/GRC-193

AN/MRC-138

AN/TSC-120

2-29.999 MHz Radio line of 

sight and 

beyond/long 

range

VHF AN/VRC-12 family:

AN/PRC-68

AN/PRC-77

SINCGARS family:

AN/PRC-119

AN/VRC-88 (A, D)

AN/VRC-89 (A, D)

AN/VRC-90 (A, D)

AN/VRC-91 (A, D)

AN/VRC-92 (A, D)

AN/GRC-213

AN/MRC-145

30-88 MHz Radio line of 

sight and 

relay/retransmission

AN/PRC-113

AN/VRC-83

116-150 MHz Critical line of

sight (ground

to air)

UHF AN/PRC-113

AN/VRC-83

AN/GRC-171

225-400 MHz Critical line of

sight (ground

to air)

AN/PSC-3

AN/PSC-5

SATCOM 

footprint
Radio Operator’s Handbook ______________________________ 2-3

High frequency communications are capable of traveling around the

world under the right conditions. This accounts for the large number of

signals and noise in the receiver (e.g., thunderstorms). Conversely, the

HF transmission may be intercepted and traced by the enemy who is

many hundreds of miles away. VHF and UHF communications are normally limited to line of sight; therefore, their range is restricted. UHF

transmissions may also be used in satellite communications, increasing

ranges to thousands of miles.

High Frequency Radio Employment Considerations. 

The primary advantage of using HF radio is its capability to provide

long-range, over the horizon (OTH) communication. Successful data

communications over the HF range depends on several factors: equipment siting, proper equipment grounding, types of antennas used, and

other considerations such as tactical employment of radio equipment,

path assessment and analysis, and frequency planning and assignment.

When commercial data terminal equipment (DTE) is used, users

employing HF radio equipment need to be aware of radio interference

and potential shock hazards that can easily affect unprotected DTE.

Whenever possible, HF radio equipment should be remoted from DTE.

Figure 2-1. AN/PRC-104 HF Radio.
2-4 _______________________________________________ MCRP 3-40.3B

High Frequency Radio Environmental Limitations

The primary limiting factors when using HF radios are frequency allocation and management and bandwidth availability. Frequency allocation

and management is concerned with frequency, time of day, time of year,

and location. The ability to reflect HF radio waves off the ionosphere to

a distant location is in a constant state of flux because of activity in the

ionosphere. The Sun’s radiation causes disturbances in the ionosphere,

with most changes taking place in what is known as the F layer (see

chapter 1 for more details). Sunrise and sunset can be the most difficult

times for HF communications. The F layer splits into two separate layers

around sunrise and recombines into one layer around sunset. These splits

affect transmission distances as the area “skipped over” increases and

decreases. At times, solar storms can eliminate all HF communications.

HF transmission paths must be constantly monitored to achieve a

dependable HF link. HF radio data communications capabilities are limited by the bandwidth that is imposed by legal constraints and the physics of the spectrum. The bandwidth available in the HF spectrum limits

the channel bandwidth, which limits data throughput. 

High Frequency Propagation

There are two modes of propagation in HF: ground wave and sky wave.

See figure 2-2.

Ground Wave. Ground wave propagation involves the transmission of a

signal along the surface of the ground. The maximum ground wave

range for most tactical HF communications is about 20 to 30 kilometers

(12 to 22 miles) for manpack equipment and 80 to 100 kilometers for

high-power vehicular and van equipment. The range may be decreased

by heavy vegetation (e.g., Camp Lejeune), mountainous terrain (e.g.,

Camp Pendleton), or dry desert soil (e.g., Twenty-nine Palms). A ground

wave circuit will generally be free of fading and may last for the entire

24-hour period without the need to change frequencies.
Radio Operator’s Handbook ______________________________ 2-5

Sky Wave. Beyond this range, it is necessary to communicate by sky

wave. Sky wave propagation involves the bending of the signal by the

ionosphere. Frequencies are very important, as those above a certain

value will not bend back to earth but will punch through the ionosphere

into outer space. On the other hand, lower frequencies are noisier and

become absorbed by the ionosphere. The reflective nature of the ionosphere will change when sunlight hits it each day. As a result, at least

two frequencies are usually required during a 24-hour period: a low,

night frequency and a higher, day frequency. 

Skip Zone

A skip zone is where no signals will be received from a particular transmitter for a particular frequency. Skip zones are formed when the nearest

point at which a sky wave is received is beyond the furthest point

at which a ground wave is received. By using an antenna with a high

Figure 2-2. HF Propagation. 

GROUND WAVE

SKIP ZONE 

SKIP ZONE 

SKY WAVE

SKY WAVE

IONOSPHERE
2-6 _______________________________________________ MCRP 3-40.3B

radiation take-off angle (i.e., the angle measured from the Earth’s surface to horizon up to the direction of propagation towards the ionosphere), HF radio waves can be bounced off the ionosphere and come

back to earth closer than they can with more commonly used antennas.

This can cause the skip zone to disappear if the waves do not punch

through. 

The use of high radiation take-off angles is called near-vertical incident

sky wave (NVIS) communications. The limit of the effective range of

NVIS communications is usually about 300 miles. NVIS communications require a horizontally polarized antenna and are done over frequencies between 2 and 12 MHz. Launch angles can be changed by altering

the antenna’s height above ground, but for most tactical applications

one-quarter wavelength above ground is sufficient. NVIS communications are particularly useful because they can be transmitted from moving vehicles. Used correctly, NVIS provides reliable, continuous

communications beyond the range of HF ground wave and VHF and

UHF line of sight. Multipath interference occurs when both the sky wave

and the ground wave signals from the transmitter arrive at different

times at the receiver. See figure 2-3. More detailed information on HF

propagation and antennas may be found in MCRP 6-22D, Antenna

Handbook. 

VERY HIGH FREQUENCY RADIO

The primary MAGTF VHF radio is the single-channel ground and airborne radio system (SINCGARS). SINCGARS is a family of lightweight combat radios that serves as the primary means of

communications for command and control and fire support on the battlefield. SINCGARS is the standard VHF-FM tactical radio for the Marine

Corps, replacing the AN/PRC-77 and the AN/VRC-12 family. The system provides high security against threat electronic warfare (EW) by

using frequency hopping with integrated COMSEC. It is capable of

voice and data transmission (up to 16 kbps under optimum conditions

and over limited distances) over the VHF-FM frequency range of 30 to

87.975 MHz. See MCRP 6-22A, Talk II SINCGARS Multiservice Communications Procedures for the Single-Channel Ground and Airborne

Radio System, for more details.
Radio Operator’s Handbook ______________________________ 2-7

There are seven different SINCGARS configurations available, depending on the requirements of the user. These configurations include the

manpack AN/PRC-119 (see figure 2-4 on page 2-8), typically used in

infantry operations, and vehicle-mounted variants. The radio provides

voice communications ranges of up to 8 km for the manpack and 35 km

for vehicular configurations. SINCGARS is capable of remote operation

by using the analog AN/GRA-39B radio remote control, the digital

HYX-57 wire-line ADAPTER, or the digital C-11561 (C)/U remote control unit (RCU).

The SINCGARS radio has undergone a systems improvement program

(SIP). This radio is referred to as the SINCGARS SIP. The primary

improvements relate to the data transmission capabilities of the system.

A forward error correction appliqué was implemented in the receiver

and/or transmitter, and a new packet data mode was created to better

support packet networks. In addition, an improved channel access protocol was added, which optimizes data throughput performance while minimizing impact on voice communications on the same SINCGARS

channel. 

Figure 2-3. Multipath Interference.

GROUND WAVE

SKY WAVE

IONOSPHERE
2-8 _______________________________________________ MCRP 3-40.3B

THE SINCGARS SIP radio is also available in a downsized version—

the result of an advanced systems improvement program (ASIP). This

radio is referred to as the SINCGARS ASIP. This radio will retain all the

functionality of the full-size SIP radio but is half the size. It weighs 7.6

pounds (including the battery). The radio is interchangeable with previous SINCGARS versions, including the capability to be mounted in

older vehicular adapter assemblies. A new feature of the SINCGARS

ASIP provides a retransmission capability while operating in the packet

data mode and will also employ a new, fast-channel access protocol for

improved operations in shared voice or data nets.

The AN/ARC-210 multipurpose radio supports single-channel air-to-air,

air-to-ground, and ground-to-air communications in tactical Navy and

Marine Corps fixed- and rotary wing aircraft. It can transmit and receive

VHF-FM, VHF-AM, and UHF signals. It is compatible with SINCGARS, HAVE QUICK, and HAVE QUICK II frequency hopping UHF

radios, and it can accept 25 preset, single-channel frequencies. The AN/

ARC-210 requires a TSEC/KY-58 encryption device to encrypt transmissions and decrypt received signals.

Figure 2-4. AN/PRC-119 SINCGARS Radio.
Radio Operator’s Handbook ______________________________ 2-9

Hand-Held Very High Frequency Radios

Radio operators may have the opportunity to use various commercial

off-the-shelf (COTS) VHF radios in the Fleet Marine Force (FMF). All

of these radios have been open-purchased by the user units and are not

part of the official Marine Corps table of equipment. Therefore, they

have not been assigned a table of authorization material control number

(TAMCN).

These hand-held radios are typically small, lightweight, battery-powered

equipment which provides clear (and in some cases secure) voice communications on up to 100 different channels. Some models come with

headsets and microphones. Hand-held radios are mostly used at the

infantry-squad level or in maritime prepositioning force (MPF) offloads. 

Very High Frequency Radio Employment Considerations 

Operator maintenance of the radio equipment, antennas, cable assemblies, and equipment grounding as well as proper planning and selection

are essential to reliable communications. Frequency separation, radio

antenna separation, remote rekeying when using COMSEC, and power

output are significant employment factors. SINCGARS may be limited

to the single-channel mode when operating with some Navy ships. When

SINCGARS is employed in the frequency hopping mode, the following

operating factors need to be taken into account: hopset (i.e., frequency

segment allocation), net sych time and mission date, antenna placement

(cosite interference is more of a concern than in the single-channel operating mode), and power setting. SINCGARS radios configured for different hopsets that dial into the same numbered net will not be able to

communicate. MCRP 6-22A provides detailed information on the

employment of SINCGARS.

VHF SCR is the primary communications system for combat and combat support units while on the move. The predominant mode of operation

is secure voice. However, use of VHF radio for data communications

will increase with the fielding of tactical information systems at the battalion level and below. Small, hand-held VHF radios are used at the

small-unit level in the MAGTF. These radios are often commercial items
2-10 ______________________________________________ MCRP 3-40.3B

that lack compatibility with SINCGARS and do not have integrated

COMSEC. Their use should be governed accordingly.

Very High Frequency Radio Environmental Limitations 

The primary limiting factors when using VHF radios are range and frequency availability. VHF radios can provide reliable communications

for ranges of up to 10 miles, depending on the equipment operating constraints and the operating environment. Unit location must be considered

when employing radios that operate in the VHF spectrum. Most circuits

are limited to radio line of sight, known as four-thirds earth curvature.

VHF radio signals essentially follow the curvature of the earth to a distance that is approximately one-third greater than the distance to the

horizon. Foliage interferes with VHF signals and may reduce normal

operating ranges to significantly less than 10 miles. 

Very High Frequency Propagation 

Radios in the SINCGARS family are the principal VHF transceivers

used by the Marine Corps. The mode of communications used in this

range is frequently referred to as frequency modulation. VHF will

extend slightly beyond line of sight due to diffraction or bending of the

signal by the atmosphere (see fig. 2-5). At frequencies in the 30-MHz

range, VHF will often act like HF ground wave. The range of reliable

communications is generally no more than 15 to 20 kilometers (9.3 to

12.4 mi) under normal field conditions for manpack equipment. Vehiclemounted equipment may communicate farther because of higher transmitter power and better antennas.

Figure 2-5. VHF Diffraction.

RECEIVING 

ANTENNA

DIFFRACTION

ANGLE

DIFFRACTED WAVE

EARTH

TRANSMITTING 

ANTENNA
Radio Operator’s Handbook _____________________________ 2-11

VHF LOS can also be plagued by multipath interference when the direct

ray and a reflected ray traveling over a slightly longer path combine at

the receiver antenna so that they periodically cancel or reinforce each

other (see fig. 2-6). The signal fades in and out over a period of time as a

result. Fading is not as great a problem with immobile equipment

because corrective action can be taken, but fading can cause significant

problems when one or more of the units are mobile. 

ULTRAHIGH FREQUENCY RADIO

Military UHF radio equipment operates in the 116 to 150 MHz upperVHF frequency range and the 225 to 400 MHz military UHF radio spectrum. MAGTF UHF radio sets such as the AN/PRC-113 (see figure 2-7

on page 2-12) are capable of data communications at 16 kbps under optimal conditions. MAGTF ground and airborne UHF radios incorporate

the HAVE QUICK Electronic Counter-Counter Measures capability and

operate in single-channel and frequency hopping modes. The HAVE

QUICK UHF radio is capable of remote operation by using the AN/

GRA-39B or HYX-57.

Ultrahigh Frequency Radio Employment Considerations 

UHF radios are used for forward air control (FAC) ground-to-air communication. Line of sight between radios is critical for reliable communications. Significant range differences are encountered between UHF

radios employed for ground-to-air and ground-to-ground communications. Greater range is achieved when employed from ground-to-air

because of the increased line of sight. When UHF radios are employed in

RECEIVING 

ANTENNA DIRECT WAVE

WAVE

REFLECTED

EARTH

TRANSMITTING 

ANTENNA

Figure 2-6. VHF LOS.
2-12 ______________________________________________ MCRP 3-40.3B

the frequency hopping mode, the following operating factors must be

understood for proper operation: hopset, time of day, antenna placement,

and power setting.

Ultrahigh Frequency Radio Environmental Limitations

The primary limiting factor when using UHF radios is range (i.e., critical

line of sight). Critical line of sight can be described as “what you see is

what you get.” As long as the radio’s antenna has optical line of sight to

another radio’s antenna, the two will be able to transmit and receive. For

this reason, UHF radios are used primarily in air-to-ground communications.

Figure 2-7. AN/PRC-113. UHF Radio.
Radio Operator’s Handbook _____________________________ 2-13

Ultrahigh Frequency-Tactical Satellite 

The AN/PSC-5 is a portable, battery-operated, half-duplex UHF transceiver. It is employed for long-range communications. It weighs approximately 14 pounds including antenna and batteries. The AN/PSC-5

provides two-way voice and data communications by satellite. It operates on the UHF frequency band of 225- to 400-MHz range. It provides

2,400 to 16,000-bits per second (bps) data rate, depending on mode setting. Only one operator is required to operate it. The United States

Marine Corps UHF tactical SATCOM system supports and augments

the high precedence command and control and common-user, singlechannel requirements of a Marine air-ground task force and its major

subordinate headquarters.

The space segments used by the AN/PSC-5 are the Fleet Satellite Communications, leased satellite communications, and UHF follow-on satellites. All the satellites are located in geosynchronous orbits and permit

interconnections among mobile, ground terminals. The one-way distance

to servicing satellites is approximately 25,000 miles, resulting in a

round-trip propagation delay of approximately one-quarter of a second.

The shape of the satellite footprints is roughly circular but elongated

from north to south. This is caused by the angle at which the signal hits

the Earth’s surface and by the curvature of the Earth’s surface.

Multiple-access schemes can operate either with fixed-channel assignments to the various users or with channels being assigned in varying

fashion according to demand. The latter is called demand assigned multiple access (DAMA). With demand assignment, the user makes a channel request, and a channel is allocated after a brief time lag. The DAMA

scheme of operation is employed on UHF-tactical satellite (TACSAT) to

share available channels more efficiently. The radio systems are compatible with the KY-57 (wideband mode only), the KY-99 and ANDVT

(narrowband mode only), and the KG-84C (wideband or narrowband)

COMSEC equipment. This radio equipment is also capable of remote

operations by using the AN/GRA-39B (narrowband mode) or HYX-57

(wide-band mode).
2-14 ______________________________________________ MCRP 3-40.3B

TACSAT Radio Employment Considerations. Because of TACSAT’s limited availability, the MAGTF employs TACSAT primarily to support

critical, long-range communications requirements (e.g., communications

support for deep reconnaissance operations or connectivity to the tactical

echelon of a MEU[SOC] when deployed ashore). The AN/PSC-5 is the

primary DAMA-capable, TACSAT radio available to the MAGTF (see

fig. 2-8). TACSAT limitations include the competition for available frequency resources and channel time on the satellite. If only narrow band

channels are available, channel-data rates are limited to 2,400 bps. Channel congestion, noise, and network saturation will affect the information

flow on satellite channels and will require a significant reduction in the

data transmission rates to sustain data communications. Transmit power

selection can be critical. Increasing the transmit power can decrease net

effectiveness. Larger directional antennas provide increased signal gain,

which increases the transmitted signal power. Antennas for these systems are lightweight and fragile and, therefore, require constant maintenance and inspection for proper operation. Satellites are shared

resources. Exact frequency, bandwidth, and power of every carrier transmitted through the satellite is strictly controlled by a higher authority.

TACSAT Radio Environmental Limitations. The primary environmental

limitations on TACSAT radios are signal propagation delay, location on

the Earth, terrain masking, and weather effects. Timing between DTE

can be a critical factor in SATCOM because the satellite, acting

as a relay between radios, is about 25,000 miles away. There is

Figure 2-8. AN/PSC-5 UHF TACSAT Radio.
Radio Operator’s Handbook _____________________________ 2-15

approximately a one-fourth second propagation delay between sending

and receiving stations. This delay can interfere with systems that automatically retransmit if an acknowledgment is not received after a very

short time-out period. As unit location changes, the “look angle” (i.e.,

angle above the horizon) to the satellite can affect net reliability. The

orbit of a satellite allows it to cover a certain footprint on the earth. Satellites in equatorial orbit can cover large portions of the Earth, both north

and south of the equator, but as the user moves closer to the Earth’s

poles, the TACSAT terminal may exceed the satellite footprint. This will

cause intermittent or lost communications. Terrain can also have this

effect by interfering with the satellite and TACSAT terminal line of

sight. Thunderstorms, heavy snowstorms, and hail also affect satellite

transmissions by damaging antennas and changing the electromagnetic

environment.

Ultrahigh Frequency Propagation

UHF frequency propagation is used for ground-to-air, air-to-air, satellite,

and tactical multi-channel communications. Communications are limited

to LOS but may extend for more than 500 kilometers as long as the aircraft is high enough to be within LOS (see fig. 2-9). It is even possible

for UHF communications ranges to a satellite to be more than 35,000

kilometers.

DATA COMMUNICATIONS

SCR can also transmit and receive data by using terminal devices such

as the digital message system (DMS)—previously called and more commonly known as the digital communications terminal (DCT)—and the

tactical communications interface module (TCIM). The DCT, data

Figure 2-9. UHF LOS.

DIRECT WAVE (LOS)

EARTH

TRANSMITTING 

ANTENNA
2-16 ______________________________________________ MCRP 3-40.3B

automated communications terminal (DACT), and the TCIM are critical

in enabling data communications at the tactical level over SCRs.

Digital Message System-AN/PSC-2

The DMS-AN/PSC-2 is a hand-held communications device that can be

operated with either a standard military radio or telephone field wire

equipment. The DMS is used to compose, edit, display, transmit, and

receive information. By menu selection, formatted text, free text, and

digitized map messages are transmitted over tactical communications

equipment. DMS is being used directly for air support, fire support

coordination, reconnaissance, medical evacuation, and other functions.

DMS uses a burst transmission capability which reduces the vulnerability to enemy radio direction finding and jamming.

Data Automated Communications Terminal

The DACT is a small, tactical computer and communications terminal

which gives users the capability to receive, process, and transmit various

messages, to include text and symbology, used by tactical data systems.

The DACT will effectively replace the DCT when it achieves full operational capability in FY 03, and it will provide much greater functionality

below battalion levels. This will include an embedded global positioning

system (GPS) receiver, the ability to share a common picture of the battlespace, automated data exchange, and MAGTF command, control,

communications, computers, and intelligence (C4I) network connectivity. The DACT will be transportable by foot-mobile Marines and

mounted in tactical or armored vehicles. 

Tactical Communications Interface Module 

The TCIM provides the communications link between the tactical computers of the communications and information systems within the

MAGTF and the local and wide area networks, switched backbone

(SBB), and radio nets. There are two versions of the TCIM card: an

internal personal computer asynchronous transfer card to mount directly

in the computer, and an external version with the card mounted in a portable chassis. TCIM software was developed for open-systems architectures. Small computer systems interfaces (SCSI) provide interoperability

between the TCIM and other Marine Corps computers. 
Chapter 3

Equipment Siting and Grounding 

Techniques

Two factors play an important role in equipment siting: optimum communications and camouflage. It is often difficult to find communications

sites which are hidden from enemy view, fire, and direction finding and

afford good communications connectivity. The ideal location for a radio

antenna is as far away from cover as possible, such as a bare mountain

top or in the middle of a large field. However, this goes against the commander’s tactical requirement for troops and equipment to be camouflaged and concealed as much as possible. Therefore, planning the

location of equipment must be detailed to achieve the best results. See

Appendix A for a review on topographical maps and grid coordinates. 

HIGH FREQUENCY

In the presence of hills (without large trees), the following guidelines for

ground wave links should be used:

l Locate HF antennas just below the top of the hill in the direction of

desired communications. Often the signal will be greater below than

on the top. This will also minimize interference and/or jamming from

the opposite direction.

l Move the antenna back from the hill if a hill is between the operator

and the distant station with which the operator wishes to communicate. The signal strength can vary widely in the region immediately

behind a hill. If it is necessary to set up behind a hill, then it may also

be necessary to set up a variety of antennas located at different distances from the hilltop to see which one offers the best performance.

Long-distance, HF sky wave signals of more than several hundred kilometers are often best transmitted and received at angles just above the

horizon level. Obstacles on the horizon will cause the signal to travel a
3-2 _______________________________________________ MCRP 3-40.3B

higher path angle and may reduce the circuit reliability as a result (see

fig. 3-1). Wire fences between the operator and the horizon will also

lessen the chances of getting through (see fig. 3-2).

An HF ground wave signal will follow the terrain much better than

higher frequency signals. It will be weakened by trees (more so when

ACTUAL PATH

REQUIRED PATH

Figure 3-1. Low HF Horizon Angles.

Figure 3-2. Effect of Wire Fences and Power Lines.
Radio Operator’s Handbook ______________________________ 3-3

they have leaves) and rugged terrain, but the signal may still get through

(see fig. 3-3).

VERY HIGH FREQUENCY AND ULTRAHIGH FREQUENCY

Obstacles such as trees, buildings, and hills between a transmitter and

receiver will weaken the signal or stop it. Aircraft flying along the path

will also interfere with reception (see fig. 3-4). A clear signal path

INTENDED PATH

SIGNAL PATH

Figure 3-3. HF Ground Wave Path.

Figure 3-4. Aircraft Along Signal Path.
3-4 _______________________________________________ MCRP 3-40.3B

between the transmitter and the intended receiver, especially for LOS

communications, is preferred. The antenna must be positioned as high as

possible to overcome obstacles, especially if communication is in the

direction of trees or buildings (see fig. 3-5). Keep equipment as far back

as possible from obstacles in the direction of the signal path to prevent

interference or damage to equipment.

In some situations, solid obstacles may actually improve a link by providing a sharper surface to diffract over or reflect from (see fig. 3-6).

INTENDED DIRECTION

 BETTER 

 GOOD 

 BAD

Figure 3-5. Antenna Obstacles.

Figure 3-6. Diffraction Over Building.
Radio Operator’s Handbook ______________________________ 3-5

Under certain conditions, spherical water towers and walls of buildings

(facing the proper direction) may enable communication around interfering terrain or vegetative obstacles (see fig. 3-7).

Transmitting over water allows VHF to go farther, but fading may occur.

If communicating over water is unavoidable, and fading occurs, the signal may be improved by raising or lowering the antenna. The antenna

may also be positioned so a hill or rise is between it and the water but not

high enough to block the LOS to the other antenna (see fig. 3-8).

Figure 3-7. Reflection off Spherical Water Tower.

Figure 3-8. Multipath Fading and Terrain Shielding.

TERRAIN SHIELDING

DIRECT PATH

REFLECTED PATH

DIRECT PATH

REFLECTED

PATH
3-6 _______________________________________________ MCRP 3-40.3B

Nothing is more compromising to a unit’s location than an antenna farm

stretched along a ridge line (see fig. 3-9). The enemy will realize that a

major command post is nearby. The advantage of placing an antenna on

a ridge line is the ability to talk in many directions without land being in

the way. If communication is needed in only one direction—away from

the enemy—put some terrain shielding between the antenna farm and

the enemy (see figures 3-10 and 3-11). This way, the enemy won’t be

able to intercept communications or jam circuits as easily. However, it’s

not always necessary to talk from hilltop to hilltop. Talking from hillside

to hillside or along the valley floor may be a better option in some

instances. The enemy will certainly have a harder time locating a unit

this way. 

Figure 3-9. Ridge Line Antenna Farm.

Figure 3-10. Low Antenna Profile.
Radio Operator’s Handbook ______________________________ 3-7

The body can act as an antenna and affect the quality of the radio signal,

particularly backpack and hand-held VHF sets with short antennas. The

effect of the body on signal strength depends on frequency, antenna

length, and the position of the antenna or set relative to the operator’s

body (see fig. 3-12 on page 3-8). 

Backpack Sets (AN/PRC-119)

Maximum radiation (i.e., best performance) is to the front when the set is

on the operator’s back with a 3-foot whip antenna. The operator should

then try facing in the direction of distant communications. This effect is

most noticeable at frequencies greater than 50 MHz.

When the set is on the ground, and the operator is very close to the set,

maximum radiation will probably occur through the operator’s body. If

the operator is a couple of feet away, the operator may act as a reflector

and either improve or interfere with the signal.

Hand-Held Sets (AN/PRC-68)

The antenna of the hand-held AN/PRC-68 is much smaller than the AN/

PRC-119’s, and the operator’s body affects directional characteristics to

INTENDED

 PATH

 

 ENEMY

Figure 3-11. Terrain Shielding.
3-8 _______________________________________________ MCRP 3-40.3B

a greater extent, particularly when the antenna is lowered. This radio

will normally be in the front jacket pocket, and best performance is then

over the back. The higher frequencies are strongly affected when the

antenna is lowered. Holding the radio in hand a few inches away from

the body will modify the radiation pattern and can substantially lower

performance to the sides at the higher frequencies. The directional characteristics of the antenna-body combination can be used to some advantage in reducing interference arriving from directions other than that of

the signal. Trial and error is necessary to make this judgment.

VHF Siting

Position the antenna to reflect the directive pattern away from the wall or

fence in the intended direction of communication when using VHF

antennas near a metal-walled building or high, metal fence. For frequencies between 30 and 50 MHz, the antenna should be placed approximately 2 meters (6.5 feet) away; between 50 and 88 MHz, no more than

1 meter (3.2 feet) away. Communications may be reduced if antennas are

placed more than 2 meters from the radio. The distance may be varied a

Figure 3-12. Direction of Best Communications.
Radio Operator’s Handbook ______________________________ 3-9

foot or so in each direction, while receiving, to find the position where

the signal is the strongest when setting up the equipment. If frequencies

are changed later, the optimum position will have to be redetermined at

that time by the same method.

UHF Siting

At UHF and (to a much lesser degree) VHF frequencies, if an operator

cannot see a person, then they probably cannot communicate—especially in heavy vegetation. Often, the signal has to travel up to the tops of

the trees and move along the treetops and down to the receiver (see fig.

3-13). This will weaken it considerably. In vegetation, the antenna

should be positioned away from trees that are in the direction of the signal and erected as high as possible. Changing the location of the antenna

is also an option. Both horizontal and vertical orientations may be used

with the AS-4225 Parabolic Grid Antenna with UHF multi-channel

(MUX) radio equipment. Horizontal polarization is usually better for

passing through the trees, but if the signal is skimming over the tops of

the trees (probably unnoticeable) or over water, then the polarization

should be vertical (see fig. 3-14 on page 3-10).

Figure 3-13. VHF Vegetative Propagation.
3-10 ______________________________________________ MCRP 3-40.3B

GROUNDING TECHNIQUES

Poor grounding is probably the most important cause of a weak HF signal. Communication distances can easily be cut in half by improper

grounding of the antenna. More importantly, the hazards involved with

improper grounding coupled with high transmitter powers are bad burns,

electrical shocks, or even death (see fig. 3-15).

Grounding prevents electrical shock to operator and improves signal

strength, particularly in HF.

HORIZONTAL VERTICAL

Figure 3-14. AS-4225 with AB-1356 Antenna Polarization.
Radio Operator’s Handbook _____________________________ 3-11

Ground Stake

The ground stake provided with the antenna should be driven deeply into

the soil, making certain all connections are tight and clean. Soil moisture

and salinity around the ground stake are very important for good grounding. If a dry or a damp location is available, choose the damp spot. If

everything is bone dry, a couple of gallons of water poured around the

stake may help. Adding a pound or two of salt from the mess tent to the

soil around the stake before soaking it may help even more.

If a regulation ground stake is not available, there are many field-expedient means for grounding. The primary concern is to provide an electrical

path from the equipment case, using braided copper or heavy gauge

wire, to a buried metallic object that is in good contact with the ground.

All cable connections and grounds should be free of grease, paint, or

rust. Cables should be as short as possible. 

Some useful grounds are—

l Metal fence posts.

l Steel reinforcing rods.

Figure 3-15. Shock Hazards of Ungrounded Equipment.
3-12 ______________________________________________ MCRP 3-40.3B

l Metal pipes.

l Metal plumbing (must not be connected to flammable liquid or gas).

l Metal building frames.

Ground Radials

A ground radial system (i.e., counterpoise) is necessary to reduce the

amount of power lost in the earth (see fig. 3-16). This is particularly

important for HF whips, inverted As, and other vertical antennas. The

radial system design is usually a compromise between performance,

portability, and time to install the system. Ground radials help to establish a known reference point of electrical ground. Without them, electrical ground may be some distance beneath the Earth’s surface. Known

electrical ground is important not only for formation of the wavefront off

the antenna, but it also affects launch angles from antennas. 

Radials are attached metal-to-metal to a central point (a metal plate is

often convenient). The radio frequency (RF) ground is attached to the

central plate (Figure 3-17).

Wire diameter is not critical; select a diameter small enough to be lightweight and transportable, but large enough to prevent breakage. The

largest number of radials to transport should be consistent with weight

and bulkiness limitations. It is not necessary to make them greater than

one-quarter wavelength at the lowest operating frequency.

LENGTH OF RADIAL = b

GROUND PLATE TO WHICH

RADIALS ARE ATTACHED

(OTHER THAN A CIRCULAR

DESIGN IS OK)

b

Figure 3-16. Radials.
Radio Operator’s Handbook _____________________________ 3-13

One-quarter wavelength = 74.9 meters 

 frequency (MHz)

Suggested dimensions:

If the site is semipermanent (i.e., several days or more), the number of

radials should be increased to 100, and their length doubled.

Make radial systems for each antenna prior to an operation. Short stakes

at the ends may be used to hold them in position when deploying.

Ground all radios, where possible. 

5 meters (15-foot whip): N (number of radials) = at least 30

(one every 12°)

b (length of radial) = 7 meters

(23 feet)

10 meters (32-foot whip): N = at least 30

b = 14 meters (46 feet)

WHIP ANTENNA 

GROUND RADIALS 

 RF GROUND 

 STAKE 

(METAL OR WOOD)

Figure 3-17. Equipment Configuration.

(reverse blank)
Chapter 4

Antennas

This chapter will discuss high frequency and very high frequency antennas. Antenna designs that work for HF sometimes work for VHF and

vice versa. The main difference is size; HF antennas are considerably

larger than VHF antennas. Ultrahigh frequency antennas are generally

limited to whips. When determining the best antenna to employ with a

circuit, consult MCRP 6-22D for more detailed information on antenna

propagation characteristics, as well as construction considerations and

procedures.

HIGH FREQUENCY ANTENNAS

Vertical Whip

A vertical whip antenna (i.e., whip) will most likely be used with an HF

radio. The whip is particularly good for ground wave communications in

many directions at one time, at distances of 20 to 30 kilometers. Unfortunately, while it is radiating in all directions at the same time, it is also

picking up interference from all directions. It is useless if using sky wave

over a distance of 100 kilometers, because of the high radiation angles

required. (NOTE: Launch angles off vertically polarized whip antennas

are maximum below 45°.) A vertical whip’s performance by sky wave,

however, improves with increased path distances.

A vehicle-mounted whip, tied down fairly close to the vehicle, may be

efficiently employed in short- and intermediate-distance HF sky wave

communications. A whip, tied back only a little, may be useful in longdistance HF sky wave applications.

Sloping Wire 

If an HF circuit is only a single point-to-point ground link or a ground

wave net with all other terminals being located in the same direction, a
4-2 _______________________________________________ MCRP 3-40.3B

sloping wire may be used, if available. The radiating length of the AT984 “Fishreel” antenna (a 45-foot long, wire antenna which can be used

with the AN/PRC-104) can be varied by either connecting or disconnecting the alligator clips. (Antenna length is measured from the radio equipment.) See Table 4-1 to determine how long an antenna should be cut to

form an assigned frequency.

 

The far end of the antenna should be connected to a rope with a weight,

such as a stone or brick or other nonconducting material tied to the end.

The weighted end should be thrown over a tree so that the antenna forms

a 30° to 45° angle to the ground. Angles higher than 45° should be used

for ground wave, and lower angles for sky wave. The high end should be

opposite the direction of the intended receiver (see fig. 4-1).

Table 4-1. Sloping Wire Antenna Lengths.

Frequency Length

MHz (Feet) (Meters)

5 45 13.7

9 25 7.6

12 15 4.6

DESIRED

DIRECTION

45

45 DEGREE SLOPING WIRE

Figure 4-1. 45° Sloping Wire Antenna.
Radio Operator’s Handbook ______________________________ 4-3

AS-2259 Near-Vertical Incidence

Another HF antenna is the AS-2259 (see fig. 4-2). Although not suitable

for frequencies under 3.5 MHz, this antenna can be used for both ground

wave and sky wave. The AS-2259 will often enable an operator to communicate in a skip zone when a whip antenna will not. In addition, it can

sometimes be used effectively to communicate by sky wave over a hill

or mountain obstacle that would otherwise block a ground wave signal.

More detailed information regarding HF NVIS antennas can be found in

MCRP 6-22D.

Horizontal Half -Wave Dipole (Doublet)

The horizontal half-wave dipole (also known as the doublet) is frequently used for short to medium HF sky wave paths (up to about 1,500

kilometers). It is usually installed at one-quarter wavelength of the operating frequency above ground (see fig. 4-3 on page 4-4). The major

drawback of this antenna is the unusually long length required (up to 71

Figure 4-2. AS-2259.
4-4 _______________________________________________ MCRP 3-40.3B

meters [233 feet] at 2 MHz). NOTE: A 2 percent or greater error in

length means less efficiency and a loss of radiated power.

Inverted L

Inverted L antennas are useful for NVIS propagation (see fig. 4-4).

Because of their construction, they also yield better ground wave radiation than whip antennas. Inverted L antennas can be effectively

employed with a wider range of frequencies than can horizontal halfwave dipole antennas.

Antenna Enhancements

Several pieces of equipment which improve the capabilities of standard

Marine Corps communications equipment are available from commercial sources. These items are not stocked in the Marine Corps supply

system. They must be purchased directly from commercial sources.

Figure 4-3. Doublet Antenna.
Radio Operator’s Handbook ______________________________ 4-5

They include—

l Tilt whip adapter (TWA)—used with the vertical whip antennas

issued with AN/MRC-138 radio. These antennas can be tilted to

obtain the correct angles for NVIS communications. The TWA made

for the AN/MRC-138 is one piece and has a simple design. When fitted with a TWA and only the top four sections of the AT-1011

antenna, the AN/MRC-138 can be operated on the move.

l Whip loading coil (WLC)—used with the WTA for the AN/MRC138. This device makes the antenna more efficient at lower frequencies.

l Whip to wire adapter (WWA)—screws into the top one-inch-diameter section of the AT-1011, thus allowing the operator to use the oneinch-diameter section of the AT-1011 as the mast for field-expedient

antennas.

INSULATORS

ANTENNA WIRE

RADIO

GROUND

LEAD WIRE

Figure 4-4. Inverted L.
4-6 _______________________________________________ MCRP 3-40.3B

l Whip-base adapter (WBA)—allows the whip antennas for Army HF

radios to be used with Marine Corps HF radios. The whip antennas

for Army HF radios are of a different size than the whip antennas for

Marine Corps HF radios. 

For further information about commercial equipment which can improve

the capabilities of Marine Corps radios, contact the G-6/S-6 sections of

higher headquarters.

VERY HIGH FREQUENCY ANTENNAS

OE-254

This antenna is used with VHF-FM radios to increase the operating

range beyond that of a normal whip. The two elements hanging down

from the antenna form a ground-plane similar to the ground radials discussed in chapter 3. The effect is to act as an artificial ground and greatly

increase the signal range. The antenna radiates in all directions at the

same time. The OE-254’s elements allow it to tune to frequencies

between 30 and 88 MHz without manually adjusting either the groundplane or radiating elements’ length. Figure 4-5 illustrates the OE-254

antenna.

Vertical Whip

VHF whip antennas are usually limited in range from 15 to 20 miles. A

whip antenna is omnidirectional; therefore, it has the potential to produce a great deal of radio-wave interference with the radios in the area. It

is important when using a whip antenna or any antenna to keep maximum distance between antennas. Use of hills and other terrain features

to block off unwanted signals will improve desired signal strength.

When using whip antennas with backpack or hand-held equipment, body

position may increase the transmitted and received signal. This is

because the human body acts as an antenna. If experiencing communication problems, the operator should try facing in different directions to

improve the reception of the signal. 
Radio Operator’s Handbook ______________________________ 4-7

ANTENNA LENGTH 

The length of an antenna must be considered in two ways. It has both a

physical and an electrical length, and the two are never the same. The

reduced velocity of the wave on the antenna and a capacitive effect

(known as end effect) make the antenna seem longer electrically than it

is physically. The contributing factors are the ratio of the diameter of the

antenna to its length and the capacitive effect of terminal equipment

(e.g., insulators, clamps, etc.) used to support the antenna. 

To calculate the physical length of an antenna, use a correction of 0.95

for frequencies between 3.0 and 50.0 MHz. The following figures are for

a half-wave antenna. 

Figure 4-5. OE-254 Antenna.

MAST SECTION

TAPE

STRAIN CLAMP

GUY ASSEMBLY

CABLE ASSY, RF

CONNECTOR

ADAPTER

ANTENNA 

ASSY

GUY 

PLATE

41’-9”

33’-8”

25’ MAX

MAST ASSEMBLY

GUY 

PLATE
4-8 _______________________________________________ MCRP 3-40.3B

Length (meters) = 150 x 0.95/Frequency in MHz 

 = 142.5/Frequency in MHz

Length (feet) = 492 x 0.95/Frequency in MHz

= 468/Frequency in MHz 

The length of a long-wire antenna (one wavelength or longer) for harmonic operation is calculated by using the following formula:

Length (meters) = 150(N-0.05)/Frequency in MHz

Length (feet) = 492(N-0.05)/Frequency in MHz

N = number of half-wave lengths in the total length of the antenna.

For example, if the number of half-wavelengths is 3 and the frequency in

MHz is 7, then:

Length (meters) = 150(N-0.05)/Frequency in MHz 

= 150(3-.05)/7

= 150 x 2.95/7

= 442.50/7

= 63.2 meters
Chapter 5

Interference

Radio frequency interference is always present in a military environment. It may come from a single source or a combination of many

sources including natural or manmade frequency interference, poor

equipment condition, improper equipment usage, frequency interference, use of unauthorized frequencies, and frequency reuse.

NATURAL INTERFERENCE

Natural radio noise has two principal sources: thunderstorms (atmospheric noise) and stars (galactic noise). It is especially noticeable at

night when the lower frequencies propagate farther than in the daytime.

The only way to reduce this type of interference is to use a directional

antenna to prevent receiving the interference from all directions. However, this will not eliminate the noise coming from the direction of the

received signal. Use of a higher frequency will also help, although if a

sky wave circuit is used, care must be exercised not to pick the highest

frequency at which the signal will be refracted to Earth by the ionosphere (i.e., the critical frequency).

MANMADE INTERFERENCE

Most manmade interference comes from electrical sources such as

power generators, alarm systems, power lines, auto ignition, fluorescent

lighting, faulty electrical relay contacts, and electrified railroads. Manmade interference also includes enemy jammers (see chapter 7). The key

to combating this form of interference is to isolate communications

equipment from manmade interference. The interference from known

sources such as generators can be greatly reduced if an antenna is positioned so that an obstacle (e.g., a hill) is between it and the source. This

must be done so that the same obstacle will not block the intended radio

path. If the interference is not coming from the same direction as the

intended signal, then a directional antenna should be used.
5-2 _______________________________________________ MCRP 3-40.3B

POOR EQUIPMENT CONDITION AND IMPROPER USAGE

The condition of radio equipment and how it is being used may result in

interference. There are several steps that should be taken to lessen this

possibility. These include making certain that shielded cables are used

where required, ensuring connectors are properly connected to cables,

and making sure that antennas within a group are as far apart as possible.

All antenna leads (transmission lines), power lines, and telephone lines

should be as short as possible when they are on the ground and should

not cross. If lines do cross, they must cross at 90° angles to each other,

and they must be separated from each other by standoffs. Lines threaded

through the trees near an antenna serve as pipelines for interference to

and from antennas. Finally, ensure that all radio equipment is grounded.

FREQUENCY INTERFERENCE AND INTERMODULATION

Frequency interference is one of the easiest communications problems to

prevent, but it must be done by the CIS officer, CIS chief, and frequency

manager during the development of the CIS plan. This type of interference is caused primarily by two radio transmitters using the same frequency, but it can also happen when different frequencies are used. Most

of these problems can be eliminated by good frequency planning. However, if frequency interference does occur the following steps can be

taken to improve communications:

l Identify the source of the interference. If it is a VHF or HF ground

wave transmission, it will probably be within the immediate area and

will only occur when the offending transmitter is keyed. The other

operator is probably transmitting on a different frequency and has no

way of knowing that he is interfering with anyone else’s ability to

transmit.

l Get the interfering operator to lower their transmitter power as long

as it does not degrade their circuit.

l Put as much distance as possible between the affected unit’s equipment. This may involve using a hill or other object to block the signal.

l Change to a directional antenna. 
Radio Operator’s Handbook ______________________________ 5-3

l Remember that the receiver of interference may also cause someone

else interference and, whenever possible, should lower his power and

use a directional antenna.

l Report interference to the CIS officer or CIS chief.

USE OF UNAUTHORIZED FREQUENCIES

There is one final source of frequency interference: the use of unauthorized frequencies. This practice is illegal and has the potential to disrupt

a carefully engineered frequency plan, introduce interference to other

frequencies and circuits, and prevent other units from fulfilling their

mission. Radio operators should never use unauthorized frequencies.

FREQUENCY REUSE

There are not enough radio frequencies available for all radio operators

to have their own channel. When HF propagation conditions are favorable, Marines may discover that their radio frequency is being used by

foreign or United States military personnel in other countries. VHF FM

frequencies often have to be reused within the same operation by more

than one unit. The exercise frequency manager will try to make certain

that users of the same frequency are as far away as possible from each

other, but some units (United States Marine Corps and Army, in particular) will join at some stage in the operation. When this occurs, the first

common, higher headquarters should be informed to settle the problem.

(reverse blank)
Chapter 6

Radio Operations Under

Unusual Conditions

OPERATIONS IN DESERT AREAS 

Capabilities and Limitations

SCR is usually the primary means of communications in the desert. It

can be employed effectively in desert climate and terrain to provide the

highly mobile means of communications demanded by widely dispersed

forces. However, desert terrain provides poor electrical ground, and

counterpoises are needed to improve operation. 

Techniques for Operations 

For the best operation in the desert, radio antennas should be located on

the highest terrain available. Transmitters using whip antennas in the

desert will lose one-fifth to one-third of their normal range because of

the poor electrical grounding characteristics of desert terrain. For this

reason, it is important to use complete antenna systems such as horizontal dipoles and vertical antennas with adequate counterpoises.

Equipment Considerations 

Some SCRs automatically switch on their second blower fan if their

internal temperature rises too high. Normally, this happens only in temperate climates when the radios are transmitting. This may disturb

Marines unaccustomed to radio operation in the desert environment.

Operation of the second fan, however, is quite normal. RF power amplifiers used in AM and SSB sets are liable to overheat severely and burn

out. They should be turned on only when necessary (signal reception is

not affected). Since the RF power amplifiers take approximately 90 seconds to reach the operating mode, the standing operating procedure

(SOP) of units using the equipment should allow for delays in replying.
6-2 _______________________________________________ MCRP 3-40.3B

Dust affects communications equipment such as SSB/AM RF power

amplifiers. Dust covers should be used whenever possible. Some

receiver-transmitter units have ventilating ports and channels that can

get clogged with dust. These must be checked regularly and kept clean to

prevent overheating. 

Batteries. Wet cell batteries do not hold their charge efficiently in intense

heat. Electrolyte evaporates rapidly and should be checked weekly

(more often, if warranted). Add distilled water as needed. Extra containers of distilled water should be carried in the vehicle. Maintenance of

vehicle batteries, beyond adding water, must be done only by authorized

motor-transport personnel according to applicable Marine Corps Orders

and SOPs. Dry battery supplies must be increased, since hot weather

causes batteries to fail more rapidly.

Electrical Insulation. Wind-blown sand and grit will damage electrical

wire insulation over a period of time. All cables that are likely to be

damaged should be protected with tape before insulation becomes worn.

Sand will also find its way into parts of items such as “spaghetti cord”

plugs, either preventing electrical contact or making it impossible to join

the plugs. Carry a brush, such as an old toothbrush, and use it to clean

such items before they are joined.

Condensation. In deserts with relatively high dew levels and high

humidity, overnight condensation can occur wherever surfaces (such as

metals exposed to air) are cooler than the air temperature. This condensation can affect electrical plugs, jacks, and connectors. All connectors

likely to be affected by condensation should be taped to prevent moisture

from contaminating the contacts. Plugs should be dried before inserting

them into equipment jacks. Excessive moisture or dew should be dried

from antenna connectors to prevent arcing.

Static Electricity. Static electricity is prevalent in the desert. It is caused

by many factors, e.g., wind-blown dust particles. Extremely low humidity contributes to static discharges between charged particles. Poor

grounding conditions exacerbate the problem. Be sure to tape all sharp

edges (tips) of antennas to cut down on wind-caused static discharges

and the accompanying noise. If you are operating from a fixed position,
Radio Operator’s Handbook ______________________________ 6-3

ensure that equipment is properly grounded. Since static-caused noise

diminishes with an increase in frequency, use the highest frequencies

that are available and authorized. 

Maintenance Improvement 

In desert areas, the maintenance of SCRs becomes more difficult

because of the large amounts of sand, dust, or dirt that enter the equipment. Radios equipped with servomechanisms are particularly affected.

To reduce maintenance downtime, keep the radios in dustproof containers as much as possible. It is also important to keep air vent filters clean

to allow cool air to circulate to prevent overheating. Preventive maintenance checks should be made frequently. Also, keep a close check on

lubricated parts of the equipment. If dust and dirt mix with the lubricants, moving parts may be damaged. 

OPERATIONS IN JUNGLE AREAS

Capabilities and Limitations 

SCR communications in jungle areas must be carefully planned because

the dense jungle growth significantly reduces the range of radio transmission. However, since SCR can be deployed in many configurations,

especially manpacked, it is a valuable communications asset. Mobility is

also an advantage of SCR. The capabilities and limitations of SCR must

be carefully considered when used by forces in a jungle environment.

Climate and density of jungle growth limits SCR communications in

jungle areas. The hot and humid climate increases the maintenance problems of keeping equipment operable. Thick jungle growth acts as a vertically polarized absorbing screen for RF energy that reduces transmission

range. Therefore, increased emphasis on maintenance and antenna siting

is necessary when operating in jungle areas. 

Techniques for Operations 

The main problem in establishing SCR communications in jungle areas

is the siting of the antenna. 
6-4 _______________________________________________ MCRP 3-40.3B

Apply the following techniques to improve communications in the

jungle: 

l Antennas should be located in clearings on the edge farthest from the

distant station and as high as possible. 

l Antenna cables and connectors should be kept off the ground to

lessen the effects of moisture, fungus, and insects. This also applies to

all power and telephone cables. 

l Complete antenna systems, such as ground planes and dipoles, are

more effective than fractional wavelength whip antennas. 

l Vegetation must be cleared from antenna sites. If an antenna touches

any foliage, especially wet foliage, the signal will be grounded. 

l Vegetation, particularly when wet, acts like a vertically polarized

screen and absorbs much of a vertically polarized signal. Horizontally

polarized antennas are preferred to vertically polarized antennas.

Maintenance Improvement 

Because of moisture and fungus, the maintenance of SCR in tropical climates is more difficult than in temperate climates. The high relative

humidity causes condensation to form on the equipment and encourages

the growth of fungus. Operators and maintenance personnel should

check the appropriate TMs for any special maintenance requirements.

Some techniques for improving maintenance in jungle areas are— 

l Keep the equipment as dry as possible and in lighted areas to retard

fungus growth. 

l Keep all air vents clear of obstructions so air can circulate to cool and

dry the equipment. 

l Keep connectors, cables, and bare metal parts as free of fungus

growth as possible. Use moisture fungusproofing paint (MFP) to protect equipment after repairs are made or when equipment is damaged

or scratched. 
Radio Operator’s Handbook ______________________________ 6-5

High Frequency Expedient Antennas 

Dismounted patrols and units of company size and below can greatly

improve their ability to communicate in the jungle by using expedient

antennas. While moving, they are generally restricted to using the short

and long antennas which come with the radios. However, when they are

not moving, these expedient antennas will allow them to broadcast farther and receive more clearly. 

Note: An antenna that is not “tuned” or “cut” to the operating frequency is not as effective as the whips that are supplied with the radio. 

Circuits inside the radio “load” the whips properly so that they are

“tuned” to give maximum output. Whips are not as effective as a tuned

doublet or tuned ground-plane, but the doublet or ground-plane must be

tuned to the operating frequency. 

OPERATIONS IN A COLD WEATHER ENVIRONMENT

Capabilities and Limitations

SCR equipment has certain capabilities and limitations that must be

carefully considered when operating in extremely cold areas. However,

in spite of significant limitations, SCR is the normal means of communications in such areas. 

One of the most important capabilities of SCR in cold weather areas is

its versatility. Vehicular-mounted radios can be moved relatively easily

to almost any point where it is possible to install a command headquarters. Smaller, manpacked radios can be carried to any point accessible by

foot or aircraft. 

A limitation on radio communications that radio operators must expect

in extremely cold areas is interference by ionospheric disturbances.

These disturbances, known as ionospheric storms, have a definite

degrading effect on sky wave propagation. Moreover, either the storms

or the auroral (e.g., Northern Lights) activity can cause complete failure

of radio communications. Some frequencies may be blocked out completely by static for extended periods of time during storm activity.
6-6 _______________________________________________ MCRP 3-40.3B

Fading, caused by changes in the density and height of the ionosphere,

can also occur and may last from minutes to weeks. The occurrence of

these disturbances is difficult to predict. When they occur, the use of

alternate frequencies and a greater reliance on FM or other means of

communications are required.

Techniques for Operations 

Whenever possible, SCR for tactical operations in cold weather areas

should be installed in vehicles to reduce the problem of transportation

and shelter for operators. This will also help solve some of the grounding

and antenna installation problems caused by the climate. 

Because of permafrost and deep snow, it is difficult to establish good

electrical grounding in extremely cold areas. The conductivity of frozen

ground is often too low to provide good ground wave propagation. To

improve ground wave operation, use a counterpoise to offset the degrading effects of poor electrical ground conductivity. Remember to install a

counterpoise high enough above the ground so that it will not be covered

by snow. 

In general, antenna installation in arcticlike areas presents no serious difficulties. However, installing some antennas may take longer because of

adverse working conditions. A few tips for installing antennas in

extremely cold areas are—

l Mast sections and antenna cables must be handled carefully since

they become brittle in very low temperatures. 

l Antenna cables should be constructed overhead to prevent damage

from heavy snow and frost, whenever possible. Nylon rope guys, if

available, should be used in preference to cotton or hemp because

nylon ropes do not readily absorb moisture and are less likely to

freeze and break. 

l Antennas should have extra guy wires, supports, and anchor stakes to

withstand heavy ice and wind loading.

Some Marine Corps radios that are adjusted to a particular frequency in

a relatively warm place may drift off frequency when exposed to
Radio Operator’s Handbook ______________________________ 6-7

extreme cold. Low battery voltage can also cause frequency drift. When

possible, allow a radio to warm up several minutes before placing it into

operation. Since extreme cold tends to lower output voltage of a dry battery, try warming the battery with body heat before operating the radio

set. This minimizes frequency drift. Flakes or pellets of highly electrically charged snow are sometimes experienced in northern regions.

When these particles strike the antenna, the resulting electrical discharge

causes a high-pitched static roar that can blanket all frequencies. To

overcome this static, antenna elements can be covered with polystyrene

tape and shellac.

Maintenance Improvement 

The maintenance of SCR equipment in extreme cold presents many difficulties. Radios must be protected from blowing snow, since snow will

freeze to dials and knobs and blow into the wiring to cause shorts and

grounds. Cords and cables must be handled carefully since they may lose

their flexibility in extreme cold. All radio equipment and power units

must be properly winterized. Check the appropriate technical manual

(TM) for winterization procedures. A few tips for maintenance in arctic

areas are discussed in the following paragraphs.

Power Units. As the temperature goes down, it becomes increasingly difficult to operate and maintain generators. They should be protected as

much as possible from the weather.

Batteries. The effect of cold weather on wet and dry cell batteries

depends upon the type and kind of battery, the load on the battery, the

particular use of the battery, and the degree of exposure to cold temperatures. 

Shock Damage. Damage may occur to vehicular SCR by the jolting of

the vehicle. Most synthetic rubber shock mounts become stiff and brittle

in extreme cold and fail to cushion equipment. Check the shock mounts

frequently and change them, as required. 

Winterization. Check the TMs for the SCR and power source to see if

there are special precautions for operation in extremely cold climates.
6-8 _______________________________________________ MCRP 3-40.3B

For example, normal lubricants may solidify and permit damage or malfunctions. They must be replaced with the recommended arctic lubricants. 

Microphones. Moisture from your breath may freeze on the perforated

cover plate of your microphone. Use standard microphone covers to prevent this. If standard covers are not available, improvise a suitable cover

from rubber or cellophane membranes or from rayon or nylon cloth. 

Breathing and Sweating. A SCR generates heat when it is operated.

When it is turned off, the air inside cools and contracts and draws cold

air into the set from the outside. This is called breathing. When a radio

breathes, and the still-hot parts come in contact with subzero air, the

glass, plastic, and ceramic parts of the set may cool too rapidly and

break. 

When cold equipment is brought suddenly into contact with warm air,

moisture will condense on the equipment parts. This is called sweating.

Before cold equipment is brought into a heated area, it should be

wrapped in a blanket or parka to ensure that it will warm gradually to

reduce sweating. Equipment must be thoroughly dry before it is taken

back out into the cold air or the moisture will freeze. 

Vehicular-Mounted Radios. These radios present special problems during

winter operations because of their continuous exposure to the elements.

Proper starting procedures must be observed. The radio’s power switch

must be off prior to starting the vehicle; this is a particularly critical

requirement when vehicles are slave started. If the radio is cold soaked

from prolonged shutdown, frost may have collected inside the radio and

could cause circuit arcing. Hence, time should be allowed for the vehicle

heater to warm the radio sufficiently that any frost collected within the

radio has a chance to thaw. This may take up to an hour. Once the radio

has been turned on, it should warm up for approximately 15 minutes

before transmitting or changing frequencies. This allows components to

stabilize. If a vehicle is operated at a low idle with radios, heater, and

lights on, the batteries may run down. Before increasing engine revolutions per minute to charge the batteries, radios should be turned off to

avoid an excessive power surge. A light coat of silicon compound on
Radio Operator’s Handbook ______________________________ 6-9

antenna mast connections helps to keep them from freezing together and

becoming hard to dismantle. 

OPERATIONS IN MOUNTAINOUS AREAS

Capabilities and Limitations

Operation of SCRs in mountainous areas has many of the same problems

as in northern or cold weather areas. Also, the mountainous terrain

makes the selection of transmission sites a critical task. In addition, the

terrain restrictions encountered frequently make radio relay stations necessary for good communications. 

Maintenance Improvement 

Because of terrain obstacles, SCR transmissions will frequently have to

be by line of sight. Also, the ground in mountainous areas is often a poor

electrical conductor. Thus, a complete antenna system, such as a dipole

or ground-plane antenna with a counterpoise, should be used. The maintenance procedures required in mountainous areas are very often the

same as maintenance in northern or cold weather areas. The varied or

seasonal temperature and climatic conditions in mountainous areas make

flexible maintenance planning a necessity. 

OPERATIONS IN SPECIAL ENVIRONMENTS

Urbanized Terrain 

SCR communications in urbanized terrain poses special problems. Some

problems are similar to those encountered in mountainous areas. There

are problems of obstacles blocking transmission paths. There is the problem of poor electrical conductivity because of pavement surfaces. There

is also the problem of commercial power-line interference. VHF radios

are not as effective in urbanized terrain as they are in some other areas.

The power output and operating frequencies of these VHF radios require

a line of sight between antennas. Line of sight at street level is not

always possible in built-up areas. 
6-10 ______________________________________________ MCRP 3-40.3B

HF radios do not require or rely on line of sight as much as VHF radios

because operating frequencies are lower, and power output is greater.

The problem is that HF radios are not organic to small units. To overcome this, the VHF signals must be retransmitted. 

Retransmission stations in aerial platforms can provide the most effective means if they are available. Organic retransmission is more likely to

be used. The antenna should be hidden or blended in with surroundings.

This will help prevent the enemy from using it as a landmark to “home

in” his artillery bombardment. Antennas can be concealed by water towers, existing civilian antennas, or steeples. 

The following steps should also be taken within urbanized terrain: 

l Park radio-equipped vehicles inside buildings for cover and concealment. 

l Dismount radio equipment and install it inside buildings (in basement, if available). 

l Place generators against buildings or under sheds to decrease noise

and provide concealment (adequate ventilation must be provided to

prevent heat buildup and subsequent failure of generator). 

Nuclear, Biological, and Chemical Environment 

One of the realities of fighting on the modern battlefield is the presence

of nuclear weapons. The explosion of a nuclear weapon causes a tremendous blast, followed by intense heat and strong radiation. The ionization

of the atmosphere by a nuclear explosion will have degrading effects on

communications because of static and the disruption of the ionosphere. 

Another effect of a nuclear explosion that is an even greater danger to

radio communications is the electromagnetic pulse (EMP). EMP is a

strong pulse of electromagnetic radiation, many times stronger than the

static pulse generated by lightning. This pulse can enter the radio

through the antenna system, power connections, and signal input connections. In the equipment, the pulse can break down circuit components

such as transistors, diodes, and integrated circuits. It can melt capacitors,

inductors, and transformers. EMP can destroy a radio. 
Radio Operator’s Handbook _____________________________ 6-11

Defensive measures against EMP call for proper maintenance, particularly the shielding of equipment. When the equipment is not in use, all

antennas and cables should be removed to decrease the effect of EMP on

the equipment. Effective grounding is necessary to reduce effect of EMP.

EMP is a danger to SCR equipment, but contamination is a danger to

Marines. Contamination from any portion of the nuclear, biological, and

chemical (NBC) environment has adverse effects on both equipment and

personnel. 

(reverse blank)
Chapter 7

Electronic Warfare

Electronic warfare (EW) is the military action involving the use of electromagnetic energy (i.e., radio frequency waves) to attack personnel,

facilities, or equipment with the intent of degrading, neutralizing, or

destroying enemy combat capability. EW includes electronic attack

(EA), electronic protection (EP), and electronic warfare support (ES). 

EA includes actions taken to prevent or reduce the enemy’s effective use

of the electromagnetic spectrum and employment of weapons that use

electromagnetic or directed energy. EP represents actions taken to protect personnel, facilities, and equipment from any effects of friendly or

enemy employment of electronic warfare that degrade, neutralize, or

destroy friendly combat capability. ES involves actions taken by, or

under direct control of, an operational commander to search for, intercept, identify, and locate sources of intentional or unintentional radiated

electromagnetic energy for the purpose of immediate threat recognition.

Each radio operator must be aware of what the enemy will try to do. The

enemy is well equipped to conduct EW, and the different techniques the

enemy uses have specific purposes in the enemy’s EW effort.

ELECTRONIC ATTACK TECHNIQUES

Enemy forces employ a large number of radio direction finder (RDF)

sets and communications intelligence (COMINT) analysts to exploit

friendly use of the electromagnetic spectrum. The enemy’s goal is to

locate and destroy as many command and control, fire support, and intelligence sites as possible during the first critical phase of the battle. When

the enemy locates sites that the enemy cannot or does not want to

destroy, these sites become prime targets for imitative electronic deception (IED) or jamming. Imitative electronic deception is the enemy’s use

of a compatible radio and a language expert to enter a friendly radio net.

The enemy IED experts are very good at their jobs. If they are permitted

to enter into a net, they will create much confusion for friendly forces.
7-2 _______________________________________________ MCRP 3-40.3B

Jamming is an effective way to disrupt control of the battle. All it takes

is a transmitter, tuned to your frequency, with the same type of modulation and with enough power output to override the signal at your

receiver. 

There are many types of jamming signals that may be used against a

radio operator. Some are very difficult to detect and some are impossible

to detect. For this reason, an operator must always be alert to the probability of jamming and react accordingly when the radio has been silent

for an inordinate amount of time. The radio operator should also be able

to quickly identify the various types of jamming signals. These

include— 

l Random noise.

l Random pulse.

l Stepped tones.

l Wobbler.

l Random keyed modulated continuous wave.

l Tone.

l Rotary.

l Pulse.

l Spark.

l Recorded Sounds.

l Gulls.

l Sweep-through.

Capture Effect and Jamming Techniques

An inherent characteristic in FM communications is that a given station

transmitting a signal will capture those receivers on the same frequency

and in range for the receiver to detect the signal. This is the basis for netted communications for VHF FM radios. This FM capture effect is undesirable when receivers in a net are “captured” by a transmitter not in that

net. This could be friendly interference or enemy interference. Friendly

interference is usually unintentional whereas enemy interference is usually intentional. 
Radio Operator’s Handbook ______________________________ 7-3

Obvious Jamming

Radio operators are mostly aware of obvious interference (e.g., jamming) by an enemy, such as stepped tones (e.g., bagpipes), randomkeyed Morse Code, pulses, and recorded sounds. The purpose of this

type of jamming is to block out reception of friendly transmitted signals

and to cause a nuisance to the receiving operator. An operator can usually detect when the enemy is using this type of jamming.

Subtle Jamming

This type of jamming is not obvious at all. With subtle jamming, no

sound is heard from the receiver. The radio does not receive incoming

friendly signals, yet everything seems normal to the operator. 

Operator Actions

Radio operators must be able to determine whether or not their radios are

being jammed. This is not always easy. Threat jammers may employ

obvious or subtle jamming techniques. These techniques may consist of

powerful unmodulated or noise-modulated carrier signals transmitted to

the operator’s receiver. Unmodulated jamming signals are characterized

by a lack of noise. Noise-modulated jamming signals are characterized

by obvious interference noises. If radio operators suspect that their

radios are the targets of threat jamming, the following procedures will

help them to make this determination.

Meaconing, Intrusion, Jamming, and Interference Report

If the radio operator suspects jamming or enemy intrusion on the net,

then the radio operator should report it immediately to higher headquarters. Such information is vital for the protection and defense of radio

communications.

Field meaconing, intrusion, jamming, and interference (MIJI) reports

serve two purposes. First, initial MIJI reports facilitate battlefield evaluations of the enemy’s actions or intentions and provide data for tactical

countermeasures, as appropriate. Second, complete and accurate followup reports ensure MIJI incidents are documented and evaluated on a
7-4 _______________________________________________ MCRP 3-40.3B

national level, thus providing data for a continuing study of foreign electronic warfare capabilities and activities. 

MIJI reports may be transmitted over nonsecure electronic means when

secure communications are not available; however, the textual content of

the MIJI report will be secured by an off-line (i.e., manual) system.

Reports will be prepared in the format outlined in the following paragraphs. Brevity numbers pertinent to specific line item information are

provided for some items. These brevity numbers must be encoded in the

numeral cipher or authentication system prior to transmission. The two

types of field MIJI reports are— 

l MIJI 1—an abbreviated initial report containing only those items of

information necessary to inform headquarters of the incident and

enable them to initiate evaluatory or retaliatory actions as appropriate.

l MIJI 2—consists of 40 lines and is completed by higher headquarters.

The MIJI 1 Report. This report is forwarded through the chain of command to the combat operations center by the operator who is experiencing the MIJI incident. A separate report is submitted for each MIJI

incident. The MIJI report includes—

l Item 1—type report. When being transmitted over nonsecure communications means, the numerals 022 are encrypted as Item 1 of the

MIJI 1 report. When being transmitted over secure communications

means, the term MIJI 1 is used as Item 1 of the MIJI 1 report. 

l Item 2—type MIJI incident. When being transmitted over nonsecure

communications means, the appropriate numeral preceding one of the

items below is encrypted as Item 2 of the MIJI 1 report. When being

transmitted over secure communications means, the appropriate term

below is used as Item 2 of the MIJI 1 report. 

 1 Meaconing

 2 Intrusion

 3 Jamming

 4 Interference
Radio Operator’s Handbook ______________________________ 7-5

l Item 3—type of equipment affected. When being transmitted over

nonsecure communications means, the appropriate numeral preceding one of the terms below is encrypted as Item 3 of the MIJI 1 report.

When being transmitted over secure communications means, the

appropriate term below is used as Item 3 of the MIJI 1 report.

 1 Radio

 2 Radar

 3 Navigational aid

 4 Satellite

 5 Electro-optics

l Item 4—Frequency or channel affected. When being transmitted over

nonsecure communications means, the frequency or channel affected

by the MIJI incident is encrypted as Item 4 of the MIJI 1 report.

When being transmitted over secure communications means, the frequency or channel affected by the MIJI incident is Item 4 of the MIJI

1 report. 

l Item 5—victim designation and call sign of affected station operator.

The complete call sign of the affected station operator is Item 5 of the

MIJI 1 report over both secure and nonsecure communications

means. 

l Item 6—coordinates of the affected station. When being transmitted

over nonsecure communications means, the complete grid coordinates of the affected station are encrypted as Item 6 of the MIJI 1

report. When being transmitted over secure communications means,

the complete grid coordinates of the affected station are Item 6 of the

MIJI 1 report. 

The MIJI 2 Report. This is a complete report containing all details of the

MIJI incident. Due to the number of items which require encryption

when the report is transmitted over a nonsecure circuit, it is recommended that the report be delivered by messenger whenever possible.

The higher headquarters’ operations officer, intelligence officer, or the

electronic warfare officer is responsible for ensuring that a complete

message report of the incident is submitted to the Joint Command and

Control Warfare Center (JC2WC) within 24 hours of the incident. 
7-6 _______________________________________________ MCRP 3-40.3B

ELECTRONIC PROTECTION TECHNIQUES

Communications security (COMSEC) is an integral part of electronic

protection. COMSEC is the protection resulting from all measures

designed to deny unauthorized persons information of value that might

be derived from the possession and study of telecommunications or to

mislead unauthorized persons in their interpretation of the results of such

possession and study. COMSEC includes transmission, cryptographic,

emission, and physical security. 

The goal of COMSEC is to protect friendly communications from

enemy exploitation while ensuring unimpeded use of the electromagnetic spectrum. The organization must be able to employ communications equipment effectively in the face of enemy efforts.

COMSEC requirements must be integrated into communications systems planning and must focus on providing secure communications

without impairing reliability or responsiveness. Modern communications equipment includes features such as an integrated encryption capability and frequency hopping capability, which contribute to

communications protection. However, the security of our communications depends on the proper operation of communications equipment and

adherence to proper procedures. 

Transmission security

Transmission security (TRANSEC) is that component of COMSEC that

results from all measures designed to protect transmissions from interception and exploitation by means other than cryptoanalysis. A message

transmitted in the clear is the enemy’s greatest source of information.

After the enemy has intercepted your radio transmission, the enemy’s

language specialists will extract all possible intelligence from it. The

enemy hopes to learn essential elements of friendly information (EEFI).

Critical information that must be protected can be remembered by the

key words SELDOM UP. 
Radio Operator’s Handbook ______________________________ 7-7

Each letter indicates a class of information as follows: 

l Strength—number of personnel, size of unit.

l Equipment—type, quantity, condition. 

l Logistics—procedure for resupply, depots.

l Disposition—were, what positions, map coordinates.

l Organization—how, what, chain of command, forces structure.

l Movement and morale—where, how, when and good or bad. 

l Units—type, designation.

l Personalities—who, where.

Using TRANSEC is absolutely essential for the radio operator. When the

radio must be used, keep transmission time to an absolute minimum (20

seconds absolute maximum: 15 seconds maximum preferred); preplan

your messages to avoid compromising any essential element of information. If you must send EEFI items, use brevity lists, if possible, and also

encrypt the message. These measures decrease your transmission, help

prevent RDF, and deny the enemy valuable information. Included under

transmission security are the authentication procedures that must be followed to protect against the enemy’s IED. Every radio operator must be

aware of the dangers of and guard against IED. 

Strict radio discipline and adherence to authorized procedures are key to

ensuring TRANSEC over SCR networks. SINCGARS radios should be

operated in a frequency hopping mode to provide maximum protection

against enemy EW capabilities. Other TRANSEC measures include—

l Well-trained operators thoroughly familiar with proper communications procedures and equipment operation. (This includes all Marines

who may operate SCR, not just CIS personnel.)

l Avoidance of unauthorized transmission and testing and maximum

use of data networks to minimize transmission time and opportunity

for enemy direction finding.

l Use of transmitter, antenna, and power combinations that produce

minimum wave propagation and emission intensity consistent with

reliable communications.
7-8 _______________________________________________ MCRP 3-40.3B

l Strict adherence to authorized frequencies.

l Use of authentication systems to protect against imitative deception

on nonsecure nets.

l Use of changing call signs and frequencies on nonsecure nets.

l Prompt response to and reporting of enemy jamming. (Operators

should continue to operate on assigned frequencies in a secure mode,

unless otherwise directed by a competent authority, and should

attempt to work through the interference.)

l Strict adherence to all emission control (EMCON) restrictions and

observance of radio silence.

l Use of communications means that do not radiate in the electromagnetic spectrum such as messengers, visual and sound signaling, and

local wire loops.

l Use of terrain masking to shield transmission systems from enemy

EW systems.

l Remoting of transmitters and avoiding the clustering of antennas.

Cryptosecurity

Cryptosecurity deals with codes, key lists, and communications security

devices. This is the third line of defense for the radio operator. If the

radio operator uses a security device on the radio, the enemy will not get

anything for the language specialists to work on. However, do not get a

false sense of security. The need for emission control and transmission

security still exists—probably more so—because, if the enemy can’t get

information, the enemy might attempt to destroy or jam your station.

Also, it is very important for all radio operators to use only authorized

codes and to realize that using homemade codes is dangerous. Homemade codes offer no protection at all. Their use is not authorized and is a

serious violation of security. 

This also includes trying to “talk around” a classified or sensitive piece

of information. The enemy intelligence personnel are not fools, and trying something like “talking around” critical information does more harm

than good. If critical information must be transmitted, it should be

encrypted or sent by secure means. In a situation when it is not possible

to send by a secure means or to encrypt a message that must be sent, the
Radio Operator’s Handbook ______________________________ 7-9

possibility of what friendly forces will lose against what the enemy

could gain must be weighed. Other factors, such as how fast the enemy

could react to the information and what delaying the message for

encryption could mean, must also be considered. 

Emission Security

Emission security (TEMPEST) is the component of COMSEC

that results from all measures taken to deny unauthorized persons

information of value that might be derived from interception and analysis of compromising emanations from cryptosecurity equipment and

telecommunications systems. The operation of communications and

information systems may result in unintentional electromagnetic emissions. Although tactical equipment is designed to reduce the possibility

of such emissions, COTS equipment is not. Unintentional emissions are

extremely susceptible to interception and analysis and may disclose classified information. Commanders must follow applicable regulations providing guidance on control and suppression of such emissions. 

Physical Security

Physical security is the COMSEC component that results from all physical measures necessary to safeguard classified equipment, material, and

documents from access or observation by unauthorized persons. The

access to classified cryptographic information must be tightly controlled.

When a commander or designated representative has determined that an

individual has a need to know and is eligible for access, then access to

classified cryptographic information will be formally authorized. The

authorization process must include an introduction to the unique nature

of cryptographic information, its unusual sensitivity, the special security

regulations governing its handling and protection, and the penalties prescribed for its disclosure. Reportable violations include—

l Loss of material.

l Unauthorized viewing.

l Capture of individuals having access to COMSEC information. 
7-10 ______________________________________________ MCRP 3-40.3B

Currently fielded COMSEC equipment is unclassified for external viewing when appropriate covers are in place and no keying material is visible. Consequently, the exposure of such equipment to casual viewing by

uncleared personnel, whether by accident or as the result of operational

necessity, does not constitute a reportable violation. 

EP techniques are divided into two categories: preventive and remedial.

Preventive EP are those procedures that can be used to avoid enemy EA

attempts. Remedial EP apply to jamming only; there are no remedial

measures once a unit has been intercepted, detected, or deceived.

ELECTRONIC WARFARE SUPPORT TECHNIQUES 

Interception

The enemy is focused on intercepting your radio signal. To do this, all

the enemy needs is a radio receiver that operates in the same mode and

on the same frequency you are using to transmit. The mere fact that you

are operating gives the enemy valuable information. It tells the enemy

that you are in the area. By the number of stations operating on the same

frequency, the enemy can estimate the size of the unit. If your net is

operating in the clear, the enemy’s language specialists can understand

exactly what is said for even more information. When analyzing the traffic pattern, the enemy can figure out which station is the net control station (NCS) and identify the headquarters. Usually, in U.S. forces, the

NCS is the radio used by the operations officer or section of the highest

headquarters operating in the net. By further traffic analysis, the enemy

can determine changes in the level of activity that could mean a movement or upcoming operation. 

Radio Direction Finding

Interception is only one of the many dangers that the radio operator will

face. After knowing friendly forces are in the area, the enemy will try to

locate their position by using radio direction finding (RDF). A radio

direction finder consists of a radio receiver, a directional antenna, and

other specialized equipment. With RDF equipment, the approximate azimuth (i.e., bearing) to a transmitting radio can be determined. One
Radio Operator’s Handbook _____________________________ 7-11

azimuth gives a general indication of direction. The intersection of two

azimuths by different RDF stations is called a cut and gives a general

indication of distance. The intersection of three or more azimuths is

called a fix and gives a general location. The ideal fix is the exact intersection of three or more bearings. However, exact intersection is seldom

achieved.

Terrain, weather, variations in radio wave propagation characteristics,

the inherent RDF equipment, and operator inaccuracies, prevent an ideal

fix. The fix that is obtained is called an actual fix. Although the actual

fix may not be usable for immediate targeting purposes, it is more than

enough for intelligence analysts to develop targeting data. Airborne

direction finding is more accurate than ground-based direction finding

but normally requires further analysis for targeting.

RDF ability to intercept electronics equipment emissions and determine

a bearing depends on the power output of the targeting transmitter and its

antenna radiation patterns. Experience indicates RDF accuracy of 500-

meter (547-yard [yd]) circular error of probability (CEP) is considered a

very good RDF fix. Normally, 50 percent of the CEPs are approximately

1,500 meters (1,640 yds) when the direction finder is located within 20

to 25 kilometers (12.4 to 15.5 mi) of the forward line of own troops

(FLOT). Many threat forces will fire on a 1,500-meter (1,640-yd) CEP if

they have sufficient massed artillery, and further analysis of terrain and

radio intercept can reduce the target area or identify an important target. 

(reverse blank)
Appendix A

Map Coordinates

Field coordinates are often expressed in universal transvers

grid coordinates and usually consist of 6-digit numbers. The t

used by the radio operator is a 1 to 50,000 scale topographi

has grid lines drawn on it, which are 1,000 meters (1 kilomet

apart. (See fig. A-1.)

To locate grid coordinate 632018, locate vertical line 63 (632

figure and draw a vertical line 2/10 of the way (632018) bet

63 and 64. Likewise, find horizontal line 01 (632018) a

LONE PINE

OLD MINEM IN E RO AD

MAIN ROAD

LON E PIN E FOR K

61

02

01

00

99

62 63 64 

(1:5

Figure A-1. Topographic Map.
horizontal line 8/10 of the way (632018) between it and line 02. 

drawn lines intersect at Lone Pine.

Similarly, the intersection of the Lone Pine Fork with the Main 

the figure would be represented as 638004, and the Old Mine w

618012.

Although the use of the 6-digit number is generally sufficient 

use, a more exact coordinate will identify the 100,000 meter sq

the grid zone designation to avoid confusion between differe

with identical grid line numbers.

A more detailed explanation of the complete coordinate may b

centered at the bottom of a 1 to 50,000 scale topographic ma

order in which the grids are read can be remembered by u

expression read-right-up.
Appendix B

Time Zones

The world is divided into 24 time zones, each one bearing a u

netic letter name (ROMEO, UNIFORM, etc.) or time zone n

must be applied to local time to arrive at the world standard 

is Coordinated Universal Time (UTC). This standard time is 

in the Marine Corps as ZULU time. (See fig. B-1.) The time 

roughly 15° apart in longitude.

ZULU TIME = LOCAL TIME - TIME ZONE NUMBER.

LOCAL TIME = ZULU TIME + TIME ZONE NUMBER.

Y X W V U I T H S G R Q P D O C N B Z A E F 

12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 345 6 7 8 9 

Figure B-1. Standard Time Zones of the World
If a Marine is in the UNIFORM time zone, (also referred to as th

8 zone), 8 hours must be added to the local time to get ZULU ti

table B-1.) On the other hand, in the ROMEO or PLUS 5 tim

1300 ZULU would equate to 0800 local. During the summer, ho

a Marine is located in an area where daylight savings time is o

one hour must be subtracted from the time zone number; i.e., the 

zone becomes the PLUS 7 zone for local time purposes.

AUTODIN communications (i.e., worldwide) ZULU time sh

used in all messages. Within the operational area, however, loca

usually used. To avoid confusion, the time zone should always b

e.g., 1100 LOCAL or 1900 ZULU.

Table B-1. CONUS Time Zones.

Civilian

Time Zone

Military

Time Zone ZULU Local

Time

ZULU

Time

EDT QUEBEC +4 0800 Q 1200 Z

EST CDT ROMEO +5 0700 R 1200 Z

CST MDT SIERRA +6 0600 S 1200 Z

MST PDT TANGO +7 0500 T 1200 Z

PST UNIFORM +8 0400 U 1200 Z
 Appendix C

Prowords

Word or

Phrase Meaning

ALL AFTER I refer to the portion of the message that 

ALL BEFORE I refer to the portion of the message that 

BREAK I hereby indicate the separation of the 

other portions of the message. Or: I h

pleted the text of the message, signatur

etc. (When break-in is permitted, receivi

tor may interrupt the transmitting op

request retransmission of a portion of a 

This proword is the interruption sign.)

CORRECTION An error has been made in this transm

message indicated). The correct 

is_______. That which follows is a corr

sion in answer to your request for verific

DISREGARD 

THIS TRANSMISSION

This transmission is in error. Disregard 

proword shall not be used to cancel any 

that has been completely transmitted 

which receipt or acknowledgment 

received.)

DO NOT 

ANSWER

Stations called are not to answer this c

for this message, or otherwise to transm

nection with this transmission. When 

word is employed, the transmission 

ended with the proword OUT.
EXECUTE Carry out the purpose of the message or si

which this applies. To be used only with th

utive method.

EXECUTE TO 

FOLOW 

Action on the message or signal which fol

to be carried out upon receipt of the p

EXECUTE. To be used only with the 

tive method.

EXEMPT The addressee designations immediately 

ing are exempted from the collective net c

FIGURES Numerals or numbers follow.

FLASH Precedence FLASH.

FROM The originator of this message is indicated 

address designation immediately following

IMMEDIATE Precedence IMMEDIATE.

INFO The addressee designations immediately 

ing are addressed for information.

I READ BACK The following is my response to your instr

to read back.

I SAY AGAIN I am repeating transmission (or portion

cated.

I SPELL I shall spell the next word phonetically.

I VERIFY The following message (or portion) has be

ified at your request and is repeated. To b

only as a reply to verify.

MESSAGE 

FOLLOWS

A message which requires recording is a

follow. (Transmitted immediately after the 

Word or

Phrase Meaning
NUMBER Station serial number.

OUT This is the end of my transmission to 

response is necessary.

OVER This is the end of my transmission to y

response is necessary. Go ahead and tran

PRIORITY Precedence PRIORITY.

READ BACK Repeat this entire transmission back to m

as received.

RELAY TO Transmit this message to all addressees 

address designations immediately follow

ROGER I have received your last transmission 

rily.

ROUTINE Precedence ROUTINE.

SAY AGAIN Repeat all of your last transmission. Fo

identification data means: “Say again 

indicated).” (“Repeat” is not used becau

signal for naval gunfire and artillery to f

SIGNALS 

FOLLOW

The groups which follow are taken fro

book. (This proword need not be used o

marily employed for conveying sign

intended for use when tactical signals a

on nontactical nets.)

SILENCE, 

SILENCE, 

SILENCE

Cease transmission immediately. (Silen

maintained until instructed to resume. 

authentication system is in force, tran

imposing silence are to be authenticated

Word or

Phrase Meaning
SILENCE 

LIFTED

Resume normal transmissions. (Silence 

lifted only by the station imposing it or by 

authority. When an authentication system 

force, transmissions lifting silence are 

authenticated.)

SPEAK 

SLOWER

Your transmission is too fast. Reduce sp

transmission.

THAT IS 

CORRECT

You are correct, or what you have transm

correct.

THIS IS This transmission is from the station whose 

nation immediately follows.

TIME That which immediately follows is the t

date-time group of the message.

TO The addressees whose designations imme

follow are to take action on this message.

UNKNOWN 

STATION

The identity of the station with whom 

attempting to e

communications is unknown.

VERIFY Verify entire message (or portion indicate

the originator and send correct version. 

used only at the discretion of or by the ad

to which the questioned message was direc

WAIT I must pause for a few seconds.

WAIT OUT I must pause longer than a few seconds.

Word or

Phrase Meaning
WILCO I have received your message, understa

will comply. (To be used only by the a

Since the meaning of ROGER is includ

of WILCO, the two prowords are ne

together.)

WORD AFTER I refer to the word that follows.

WORD BEFORE I refer to the word that precedes.

WORDS TWICE Communication is difficult. Transmit(t

phrase (or each code group) twice. Thi

may be used as an order, request, or as 

tion.

WRONG Your last transmission was incorrect. T

version is.

Word or

Phrase Meaning

(reve
Appendix D

Phonetic Alphabet

Letter Word Pronunciation

A ALFA AL FAH

B BRAVO BRAH VOH

C CHARLIE CHAR LEE

D DELTA DELL TAH

E ECHO ECK OH

F FOXTROT FOKS TROT

G GOLF GOLF

H HOTEL HOH TELL

I INDIA IN DEE AH

J JULIETT JEW LEE ETT

K KILO KEY LOH

L LIMA LEE MAH

M MIKE MIKE

N NOVEMBER NOVEMBER

O OSCAR OSS CAH

P PAPA PAH PAH

Q QUEBEC KEH BECK

R ROMEO ROW ME OH

S SIERRA SEE AIR RAH

T TANGO TANG GO
U UNIFORM YOU NEE FORM

V VICTOR VIK TAH

W WHISKEY WISS KEY

X XRAY ECKS RAY

Y YANKEE YANG KEY

Z ZULU ZOO LOO

Letter Word Pronunciation
Appendix E

Phonetic Numerals

Number Pronunciation

1 WUN

2 TOO

3 TREE

4 FOW-er

5 FIFE

6 SIX

7 SEV-en

8 AIT

9 NIN-er

0 ZERO

(reve
Appendix F

Prosigns

Prosign M

AA .....................................................................................................

AB .....................................................................................................

AR .....................................................End of transmission. No rece

AS...................................................................... I must pause for a f

AS AR ..................I must pause longer than a few seconds. Will ca

B ..................................................................................................Mo

BT......................................................................................................

C ........................................................................................................

DE......................................................................................................

EEEEEEEE .......................................................................................

EEEEEEEE AR .......................................This message is in error. D

F....................................................................................................Do 

FM .....................................................................................................

G ......................................................Repeat this entire transmission 

GR ...................................................................................................G

GRNC ................................. The groups in this message have not be

HM HM HM..................................................... Emergency silence s
IMI .........................................................................................................

INFO .................................The address designations immediately follo

addressed for informa

INT..................................................................................................Inter

IX ......................Action on the message or signal which follows is to b

out upon receipt of 

J.......................................................................Verify with originator an

K.................................This is the end of my transmission to you and a 

is n

NR......................................................................... Numerals or numbe

O...................................................................................... Immediate pre

P ........................................................................................... Priority pre

R...........................................................................................Routine pre

T.............................................................................................................

TO ............................................................................................Action a

WA ..................................................................................................... W

WB .................................................................................................. Wor

XMT.......................................................................................................

Y.................................................................... Emergency command pre

Z...............................................................................................Flash pre
Appendix G

Instructions for Preparing

Field Messages

1. Place the protector insert under the message blanks to lim

ber of copies produced. Retain one copy in the book as a 

Classify cover in accordance with contents (see fig. G-1).

2. Use BLOCK CAPITAL letters for all entries except the 

Use necessary punctuation.

3. To assign precedence and classification use table on the ne

4. If a classified message is to be transmitted, secure voic

clear, check appropriate block.

5. Show organization originating message in FM (from) bloc

6. Show organization(s) for whom the message is intended 

block.

7. Block labeled date-time group is for communication perso

8. Draft the message in brief but clear terms.

9. Message drafters are responsible for all message drafting 

to include the use of brevity codes. 
PRECEDENC E TABLE SECURITY CLASSIFICATION 

Z - FLASH TOPSEC - TOP SECRET

O- SECRET - SECRET IM MEDIATE

P - PRIORITY CONF - CONFIDENTIA

R - ROUTINE UNCLAS - UNCLASSIFIE

PROTECTOR INSERT

Place this under the last copy of each message written.

SAMPLE MESSAGE

PREC.

TO:

BT

BT

TOR TOD

SEND

SECURE

VOICE

SEND

CLEAR

RELEASING OFFICER’S SIGNA

CLASS

INFO.

DTG FM:

X

Figure G-1. Sample Message.
Appendix H

Radio Log

(

Radio Circuit Log (Marine Corps)

Circuit Bn TAC Station Call A2C Other stations

Net ID/Frequency

556

Net Control Station X4L J4Z

M2P

Operator PFC Jones, A Net Call Sign S5F

Supervisor Sgt. Smith, J Page 01 of 10 Date 6 OCT 99

Time Call Transmission 

0800Z Assumed watch

0801 B6D DE A2C

A2C DE B30

A2C DE D5F

K

K

K

0804 B3D C3E

D5F DE A2C AR

0808 A2C DE B3D

B3D DE A2C

A2C DE B3D

K

K

P 23140OZ SEP 99 C Files

0810 B3D DE A2C AR 

0812 B6D DE A2C Abbreviated Calls Authorized AR 

0815 C4E DE D5F K 

DE E K

DE F MSG 0 231414Z SEP 99

FM D5F3

TO C4E3

BT

Classified (Use Actual Classification)

Report to CAR Dealer at 1000 Today for 

Liaison

BT

K

(reve
 Appendix I

Metric System Conversion Tabl

The basic unit of the metric system is the meter (m). The me

inches long. This is 3.37 inches longer than the English yard

are multiples or fractional parts of the meter are designated b

to the word “meter.”

1 millimeter (mm) = 0.001 meter or 1/1000 mete

1 centimeter (cm)= 0.01 meter or 1/100 meter 

1 decimeter (dm) = 0.1 meter of 1/10 meter

1 decameter (dkm) = 10 meters

1 hectometer (hm) = 100 meters

1 kilometer (km) = 1000 meters

The Metric Measurement in Most Common Use

10 millimeters = 1 centimeter

10 centimeters = 1 decimeter

10 decimeters = 1 meter

1000 meters = 1 kilometer

To Convert 

Length Multiply by

Inches to centimeters 2.54

Feet to meters 0.3048

Yards to meters 0.9144

Miles to kilometers 1.609

Millimeters to inches 0.03937

Centimeters to inches 0.3937

Decimeters to inches 3.937

Decimeters to feet 0.328

Meters to inches 39.37
Meters to feet 3.28

Meters to yards 1.0936

Decameters to feet 32.8

Hectometers to feet 328.1

Kilometers to feet 3281

Kilometers to yards 1093.6

Kilometers to miles 0.62

Examples:

To change 90 kilometers to miles: 90 x .62 = 55.8 miles

To change 90 kilometers to feet: 90 x 3281 = 295,290 feet

To change 50 yards to meters: 50 x 0.9144 = 45.72 meters
Appendix J

Authentication

Authentication systems are provided to prevent unauthorized 

tions from entering friendly radio nets to disrupt or confuse 

The only authentication systems authorized are those approv

by the National Security Agency. If a special or emergency r

arises, notify the CIS officer (G-6/S-6).

INSTRUCTIONS

There are two methods of authentication that are authorize

challenge and reply authentication and transmission authentic

operational distinction is that challenge and reply require

communications, whereas transmission authentication does no

Challenge and Reply Authentication

Challenge and reply authentication will be used whenever po

called party will always make the first challenge. Besides val

authenticity of the calling station, this practice prevents an en

tor from entering a net to obtain correct authentication respon

in another net. The party making the call may countercha

called party using a different challenge.

Note: In challenge and reply authentication, only the statio

ing is verified. Do not accept a challenge as an authenticatio

When a caller desires authentication, he must invite a challen

ing that he is prepared to authenticate.

Another challenge should be made if an incorrect reply is re

standby is requested, or if an unusual delay occurs between 

and reply.
Users will occasionally misauthenticate because of such prob

having the wrong system, misreading the table, etc. The challen

tion should attempt to pinpoint the difficulty and then rechalleng

Never give the challenge and reply in the same transmissi

authentication).

Transmission Authentication

Transmission authentication is used to validate the authenticit

message when it is impossible or impractical to use challenge a

authentication (see table J-1).

For Instructional Purposes Only

Table J-1. Sample AKAC-874 Transmission Authenticat

18 19 20 21 22 

0 SD IU PY UT JG 

2 FG KG AG RG YR 

4 VF DY KU JM RW 

6 HD ML DT SC DA 

8 RD NB MG GR LJ 

10 BJ FR SR EF MB 

12 JH SP PO QS VX 

14 TY OL RM OL FS 

16 DR IJ AO MJ HD 

18 JH TL KY BG UY 

20 SD WM SR DE GC 

22 MJ AP GH FD JG 

24 BN PC FI KI RW 
WHEN TO AUTHENTICATE

Transmission should be authenticated—

l When any station suspects imitative deception on any c

when contacting a station following one or more un

attempts to contact that station.

l When any station is challenged or requested to authentic

not to be interpreted as requiring stations to break an impo

for the sole purpose of authenticating.

l When directing radio silence, listening silence, or requirin

to break an imposed silence.

l When transmitting contact and amplifying reports in plain 

l When transmitting operating instructions that affect the m

ation; e.g., closing down a station or watch, changing frequ

than normal scheduled changes, directing establishment o

communication guard, requesting artillery fire support, dire

cation of units, etc.

l When transmitting a plain language cancellation.

l When making initial radio contact or resuming contact 

longed interruptions.

l When transmitting to a station that is under radio listening 

l When authorized to transmit a classified message in the cle

l When forced, because of no response by the called statio

message in the blind (transmission authentication).

Note: Authentication is not required when making initial co

a scheduled call sign and frequency change since only bon

tions will know their assigned call sign and frequency fo

period in use.

For detailed authentication instructions refer to the automated 

cations-electronics operations instructions.

(reve
Appendix K

International Morse Code

Dots and dashes are used in various distinctive combination

sent the letters of the alphabet, the numerals from 0 to 9, an

igns (see fig K-1). The dots and dashes of the Morse Code ar

by keying a transmitter and causing it to transmit short and lo

The dash is 3 times the length of the dot. The dots and dashes 

letter are spaced from each other by a period of time equal i

one dot. Letters are spaced from each other by a period of tim

three dots. Words are spaced by a period of time equal to sev

a. Letters

b. Figures

A J S 

E N W 

F O X 

G P Y 

H Q Z 

I R 

B K T 

C L U 

D M V 

1 5 9

2 6 0

3 7

4 8

Figure K-1. Morse Code.

(reve
Appendix L

Frequency Prediction Means

Radio signals propagate from a transmitter to a receiver in diff

depending on the selected frequency of the radio. The two 

resources for Marines to predict the best frequency to propa

given path are to use the Joint Spectrum Center (JSC) or t

Corps’ system planning, engineering, and evaluation device 

See figure L-1 on page L-2.

JSC is a Department of Defense agency that is responsible for 

the electromagnetic analysis to the uniformed services. L

Annapolis, Maryland, JSC can perform a variety of propagat

tions on all ranges of frequencies. Once a quarter, JSC publish

HF frequency predictions for selected paths that the Marine 

requested. A compilation of frequency predictions are held 

offices of the major subordinate commands within the Marine 

The second method is SPEED. SPEED is computer software 

communications system planners to do rapid analysis of r

propagation. The SPEED comes with electronic maps of the E

allow true line of sight data for the planners, as well as HF p

prediction. SPEED is available down to the battalion level.
RADIOS, RADARS,

 SENSORS PLRS

SINCGARS

 RADIO

PATH PROFILING

 SPEED SUPPORTS...

 AREA COVERA

 AND REFEREN

 UNIT PLACEME

FREQUENCY

 HOPSET

GENERATION

TRI-TAC

 SW ITCHING A

 MULITICHANN

 PROGRAMMI

Figure L-1. SPEED.
Appendix M

Position and Navigation System

Global positioning system (GPS) and position location report

(PLRS) are new systems that radio operators may be required 

GLOBAL POSITIONING SYSTEM

Global positioning system is a space-based navigation system 

to provide 24-hour continuous worldwide, all-weather precis

and time measurement. The GPS consists of a space segment 

control segment (monitors stations on Earth), and user segm

receivers). The system operates by satellites sending out two 

nonchanging frequencies. The GPS receiver receives the sig

mitted by the satellites and computes the users position. GPS 

an all-weather, jam-resistant, continuous system) gives us

accurate navigation; worldwide, three-dimensional position 

velocity; and time information. As a passive, receive-only sy

can be employed at the individual level in such nondescrip

jungles, mountain ranges, or deserts. (See fig. M-1 on page M

POSITION LOCATION REPORTING SYSTEM

PLRS is a system of UHF radios, signal and message proc

user input and output devices configured as master stations 

units that provide the user of the system with position naviga

mation and limited digital communications. PLRS works by t

ual units in the network time sharing a single frequency ba

master station records the arrival time of the signal bursts from 

unit at given locations, the range between sender and recei

computed. If units are beyond line of sight for the master st

PLRS will automatically enable any user unit to serve as an 

relay. The full PLRS performance can be provided over a 

kilometer operating area. This operating area can be extende

by 300-kilometer area through the use of airborne relays p

PLRS-equipped aircraft. 
ENHANCED POSITION REPORTING SYSTEM

Enhanced position location reporting system (EPLRS) share

characteristics with PLRS, but provides a significant increase 

communications capability over PLRS. Various data rates supp

variety of broadcast and point-to-point modes are currently a

EPLRS will provide a dedicated data communications c

between regiment and battalion tactical data networks (TDNs) w

ground combat element, when fielded in FY-00. This network 

be extended to lower echelons throughout the MAGTF. EPLRS 

serve as a source for automated friendly position location info

and navigation information in a hybrid community with PLRS

data throughput is reduced.

W H EN THE GPS IS COM PLETELY

IN STALLED, AT LEAST FO UR SATELLITES

W ILL ALWAYS BE IN VIEW W ORLDW IDE

AND W ILL CONTIN UOUSLY TR ANSMIT

THEIR POSITION AND TIME OF

TRANSMISSION.

GPS RECEIVER

MEASURES TRANSIT T

OF EACH SIGNAL AND

COMPUTES USER POS

AND DESIRED NAVIGA

DATA.

Figure M-1. Global Positioning System.
REG

REG

REG

Bn

Bn Co Co

AN /M R C -1

 LOS MUX

EPLRS

SINCGARS 

Plt

Plt

Plt

DIV

Bn

Figure M-2. EPLRS Concept of Employment.

(reve
Appendix N

Size of Dipole and Inverted L

Antennas

ACCORDING TO WAVELENGTH MEASUREME

Size of dipole and inverted L antennas according to w

measurements (in feet and inches).

 

Table N-1. Size of Antennas

Frequency 1/2 Wavelength 1/4 

Wavelength

1/8 

Wavelength 

Wa

2.00 225 ft 6 in 112 ft 9 in 56 ft 4 1/2 in 1,12

2.50 180 ft 4 3/4 in 90 ft 2 1/3 in 45 ft 1 in 901 

3.00 150 ft 4 in 75 ft 2 in 37 ft 7 in 751 

3.50 128 ft 10 1/4 in 64 ft 5 in 32 ft 2 in 644 

4.00 112 ft 9 in 56 ft 4 1/2 in 28 ft 21/2 in 563 

4.50 100 ft 2 2/3 in 50 ft 11/3 in 25 ft 2/3 in 501 

5.00 90 ft 2 1/3 in 45 ft 1 in 22 ft 6 2/3 in 450 

5.50 82 ft 41 ft 20 ft 6 in 410 

6.00 75 ft 2 in 37 ft 7 in 18 ft 9 1/2 in 375 

6.50 69 ft 4 2/3 in 34 ft 8 1/3 in 17 ft 4 in 346 

7.00 64 ft 5 in 32 ft 2 1/2 in 16 ft 1 1/4 in 322 

7.50 60 ft 1 2/3 in 30 ft 1 in 15 ft 1/3 in 300 

8.00 56 ft 4 1/2 in 28 ft 2 1/4 in 14 ft 1 in 281 

8.50 53 ft 3/4 in 26 ft 6 1/8 in 13 ft 3 1/8 in 265 

9.00 50 ft 1 1/3 in 25 ft 2/3 in 12 ft 1/3 in 250 

9.50 47 ft 5 2/3 in 23 ft 8 3/4 in 11 ft 10 1/3 in 237 

.
10.00 45 ft 1 in 22 ft 6 2/3 in 11 ft 1/4 in 225 ft 6 

10.50 42 ft 11 2/3 in 21 ft 5 3/4 in 10 ft 8 3/4 in 214 ft 9 

11.00 41 ft 20 ft 6 in 10 ft 3 in 205 ft 

11.50 39 ft 2 2/3 in 19 ft 7 1/2 in 9 ft 9 2/3 in 196 ft 1 

12.00 37 ft 7 in 18 ft 9 1/2 in 9 ft 4 3/4 in 187 ft 1

12.50 36 ft 1 in 18 ft 1/2 in 9 ft 1/4 in 180 ft 4 

13.00 34 ft 8 1/3 in 17 ft 4 in 8 ft 8 in 173 ft 5 

13.50 33 ft 5 in 16 ft 8 1/2 in 8 ft 4 1/4 in 167 ft 3

14.00 32 ft 2 1/2 in 16 ft 1 1/4 in 8 ft 2/3 in 161 ft 3

14.50 31 ft 1 1/4 in 15 ft 6 2/3 in 7 ft 9 1/3 in 155 ft 6 

15.00 30 ft 1 in 15 ft 1/3 in 7 ft 6 1/4 in 150 ft 4 

15.50 29 ft 1 1/8 in 14 ft 6 1/2 in 7 ft 3 1/4 in 145 ft 5 

16.00 28 ft 2 1/4 in 14 ft 1 1/8 in 7 ft 1/2 in 140 ft 1

16.50 27 ft 4 in 13 ft 8 in 6 ft 10 in 136 ft 

17.00 26 ft 6 1/3 in 13 ft 3 1/8 in 6 ft 7 1/2 in 132 ft 7 

17.50 25 ft 9 1/4 in 12 ft 10 2/3 in 6 ft 5 1/3 in 128 ft 1

18.00 25 ft 2/3 in 12 ft 6 1/3 in 6 ft 3 1/8 in 125 ft 3 

18.50 24 ft 4 1/2 in 12 ft 2 1/4 in 6 ft 1 1/8 in 121 ft 1

19.00 23 ft 8 3/4 in 11 ft 10 3/8 in 5 ft 11 1/4 in 118 ft 8 

19.50 23 ft 1 1/2 in 11 ft 6 3/4 in 5 ft 9 3/8 in 115 ft 7 

20.00 22 ft 6 1/2 in 11 ft 3 1/4 in 5 ft 7 2/8 in 112 ft 9 

20.50 22 ft 11 ft 5 ft 6 in 110 ft

21.00 21 ft 5 3/4 in 10 ft 8 1/8 in 5 ft 4 3/8 in 107 ft 4 

21.50 20 ft 11 3/4 in 10 ft 5 1/8 in 5 ft 3 in 104 ft 1

22.00 20 ft 6 in 10 ft 3 in 5 ft 1 1/2 in 102 ft 6 

22.50 20 ft 1/2 in 10 ft 1/4 in 5 ft 1/8 in 100 ft 2 

Table N-1. Size of Antennas

Frequency 1/2 Wavelength 1/4 

Wavelength

1/8 

Wavelength 

2 

Wave

(M

(continued)
23.00 19 ft 7 1/3 in 5 ft 9 2/3 in 4 ft 10 1/8 in 98 ft 

23.50 19 ft 2 1/4 in 9 ft 7 1/8 in 4 ft 9 in 95 ft 

24.00 18 ft 9 1/2 in 9 ft 4 3/4 in 4 ft 8 3/8in 93 ft 

24.50 18 ft 5 in 9 ft 2 3/8 in 4 ft 7 1/4 in 92 ft 

25.00 18 ft 1/2 in 9 ft 1/4 in 4 ft 6 1/8 in 90 ft 

25.50 17 ft 8 1/4 in 8 ft 10 1/8 in 4 ft 5 in 88 ft 

26.00 17 ft 4 1/8 in 8 ft 8 in 4 ft 4 in 85 ft 

26.50 17 ft 1/4 in 8 ft 6 1/8 in 4 ft 3 in 85 ft 

27.00 16 ft 8 3/8 in 8 ft 4 1/4 in 4 ft 2 1/8 in 83 ft 

27.50 16 ft 4 3/4 in 8 ft 2 3/8 in 4 ft 1 1/8 in 81 ft 

28.00 16 ft 1 1/4 in 8 ft 2/3 in 4 ft 1/3 in 80 ft 

28.50 15 ft 9 1/8 in 7 ft 11 in 3 ft 11 1/2 in 79 ft 

29.00 15 ft 6 2/3 in 7 ft 9 1/3 in 3 ft 10 2/3 in 77 ft 

29.50 15 ft 3 1/2 in 7 ft 7 3/4 in 3 ft 10 in 76 ft 

30.00 15 ft 3/8 in 7 ft 6 1/8 in 3 ft 9 in 75 ft 

Table N-1. Size of Antennas

Frequency 1/2 Wavelength 1/4 

Wavelength

1/8 

Wavelength 

Wa

(continue

(rever
Appendix O

Field Repair and Expedients

Section I. Antenna Repair

Antennas are sometimes broken or damaged, causing either a 

cations failure or poor communications. If a spare is availab

the damaged antenna. When there is no spare, you may have t

an emergency antenna. The following paragraphs are sugg

repairing antennas and antenna supports and on constructing 

ing emergency antennas. 

REPAIR TECHNIQUES 

Whip Antennas 

When a whip antenna is broken into two sections, the por

antenna that is broken off can be connected to the portion atta

base by joining the sections as shown in figure O-1 on page O

method illustrated in figure O-1A, when both parts of the br

are available and usable. Use the method shown in figure O-1B 

portion of the whip that was broken off is lost, or when the wh

damaged. To restore the antenna to its original length, add 

wire that is nearly the same length as the missing part of the w

lash the pole support securely to both sections of the antenna

two antenna sections thoroughly to ensure good contact befor

ing them to the pole support. If possible, solder the connectio

Wire Antennas 

Emergency repair of a wire antenna may involve the repair 

ment of the wire used as the antenna or transmission line; or

or replacement of the assembly used to support the antenna. 
When one or more wires of an antenna are broken, the antenn

repaired by reconnecting the broken wires. To do this, lower the 

to the ground, clean the ends of the wires, and twist the wires 

Whenever possible, solder the connection. 

If the antenna is damaged beyond repair, construct a new one. M

that the lengths of the wires of the substitute antenna are the sam

as the original. 

Antenna supports may also require repair or replacement. A s

item may be used in place of a damaged support and, if prope

lated, can be of any material of adequate strength. If the radia

ment is not properly insulated, field antennas may be shorted to 

and rendered ineffective. Many commonly found items can be 

field expedient insulators. The best of these items are plastic or 

include plastic spoons, buttons, bottle necks, and plastic ba

effective than plastic or glass but better than no insulators at all a

and rope, or both, in that order. The radiating element—th

antenna wire—should touch only the antenna terminal and be ph

POLE OR 

BRANCH

CABLE OR 

TAPE 

LASHING

CABLE OR 

TAPE 

LASHING

BREAK

A B

REPLACEM

FIELD 

POLE OR 

BRANCH

(LENGTH OF

BROKEN

ANTENNA)

Figure O-1. Emergency Repair of Broken Whip.
separated from all other objects, other than the supporting ins

ure O-2 shows various emergency insulators. 

Guys 

Lines used to stabilize the supports for an antenna are called g

lines are usually made of wire, manila rope, or nylon rope

breaks, it may be repaired by tying the two broken ends toge

rope is too short after the tie is made, it can be lengthened 

another piece of dry wood or cloth. If a guy wire breaks

PLASTIC SPOON

NYLON ROPE

BUTTON

PLASTIC BAG

BOTTLE NECK

WOOD(DRY)

RUBBER OR CLOTH STRIP(DRY)

NYLON ROPE

BEST

GOOD

FAIR

Figure O-2. Improvised Insulators.
replaced with another piece of wire. Figure O-3 shows a m

repairing a guy line with a spoon. 

Masts 

Some antennas are supported by masts. If a mast breaks, it 

replaced with one of same length. If long poles are not ava

replacements, short poles may be overlapped and lashed toget

rope or wire to provide a pole of the required length. Figure O-3 

method of making an emergency repair to masts. 

Figure O-3. Repaired Guy Lines and Masts.
TIPS FOR CONSTRUCTION AND ADJUSTMEN

Constructing the Antenna 

The best kinds of wire for antennas are copper and alumin

emergency, however, use any type that is available. 

The length of most antennas is critical. The emergency ante

be the same length as the antenna it replaces. 

Antennas supported by trees can usually survive heavy win

the trunk of a tree or a strong branch is used as a support. T

antenna taut and to prevent it from breaking or stretching a

sway, attach a spring or old inner tube to one end of the antenn

technique is to pass a rope through a pulley or eyehook, attac

to the end of the antenna, and load the rope with a heavy wei

the antenna tightly drawn. 

Guys used to hold antenna supports are made of rope or wire

that the guys made of wire will not affect the operation of th

cut the wire into several short lengths and connect the pieces w

tors. 

Adjusting the Antenna 

An improvised antenna may change the performance of a rad

the following methods to determine if the antenna is operating 

A distant station may be used to test the antenna. If the sign

from this station is strong, the antenna is operating satisfacto

signal is weak, adjust the height and length of the antenna an

mission line to receive the strongest signal at a given setting 

ume control of the receiver. This is the best method of tuning 

when transmission is dangerous or forbidden. 

In some radio sets, the transmitter is used to adjust the antenn

the controls of the transmitter in the proper position for nor

tion; then, tune the system by adjusting the antenna height, t
length, and the transmission line length to obtain the best tran

output. 

Impedance-matching a load to its source is an important conside

transmissions’ systems. If the load and source are mismatched

the power is reflected back along the transmission line tow

source. This reflection not only prevents maximum power tran

can also be responsible for erroneous measurements of other par

or even cause circuit damage in high-power applications. 

The power reflected from the load interferes with the incident (

ward) power, causing standing waves of voltages and current 

along the line. The ratio of standing-wave maxima to minima is 

related to the impedance mismatch of the load; therefore the s

wave ratio (SWR) provides the means of determining impeda

mismatch. 

WARNING

SERIOUS INJURY OR DEATH CAN RESULT FROM CO

WITH THE RADIATING ANTENNA OF A MEDIUM- OR HIG

ER TRANSMITTER. TURN THE TRANSMITTER OFF WHIL

 ING ADJUSTMENTS TO THE ANTENNA.
Section II. Field Expedient Antennas

SINCGARS VHF radios provide the primary means of comm

for Marine Corps forces around the world. The SINCGARS 

ates in both single-channel and frequency hopping modes. It i

for CIS personnel to remember that when using the SINCGAR

the frequency hopping mode, field expedient VHF antennas 

be used. CIS personnel should only use the whip antenna or t

antenna when operating in the frequency hopping mode.

HIGH FREQUENCY, FIELD EXPEDIENT 

OMNIDIRECTIONAL ANTENNAS 

Vertical antennas are omnidirectional; i.e., they transmit a

equally well in all directions. Most manpack portable ra

vertical whip antenna. A vertical antenna can be improvised 

metal pipe or rod of the correct length, held erect by means of 

lower end of the antenna should be insulated from the ground 

it on insulating material. A vertical antenna may also be a 

ported by a tree or a wooden pole (see fig. O-4). For sho

INSULATOR

GROUND 

STAKE

GROUND

STAKE

ANTENNA 

WIRE

ANTENNA 

WIRE

WOODEN 

POLE

INSULATOR

INSULATOR

Figure O-4. Field Substitutes for Support of Vertica

Wire Antennas.
antennas, the pole may be used without guys (if properly supp

the base). If the length of the vertical mast is not long enough to 

the wire upright, it may be necessary to modify the connection a

of the antenna. 

End-Fed Half-Wave Antenna 

An emergency, end-fed half-wave antenna can be construct

available materials such as field wire, rope, and wooden insulat

electrical length of this antenna is measured from the antenna 

on the radio set to the far end of the antenna (see fig. O-5). Cons

antenna longer than necessary, then shorten it, as required, u

results are obtained. The ground terminal of the radio set should 

nected to a good Earth ground for this antenna to function effici

Center-Fed Doublet Antenna 

The center-fed doublet is a half-wave antenna consisting of two, 

wavelength sections on each side of the center. Constructio

improvised doublet antenna for use with FM radios is shown i

O-6. 

INSULATORS

GROU

STA

ANTENNA 

WIRE

WOODEN 

MAST

Figure O-5. End-Fed Half-Wave Antenna.
Doublet antennas are directional broadside to their length, wh

the vertical doublet antenna essentially omnidirectional. This 

the radiation pattern is doughnut shaped. The horizontal doub

is bidirectional. 

The length of a half-wave antenna may be computed by usi

mula in Chapter 4. Cut the wires as closely as possible to 

length because the length of the antenna wires is important. 

A transmission line is used for conducting electrical energy 

point to another, and it is used to transfer the output of a transm

antenna. Although it is possible to connect an antenna directly 

mitter, the antenna generally is located some distance away. I

lar installation, for example, the antenna is mounted outsid

transmitter is inside the vehicle. A transmission line, therefor

sary as a connecting link. 

Center-fed half-wave FM antennas can be supported entirely 

of wood. A horizontal antenna of this type is shown in figu

vertical antenna in figure O-7B on page O-10. These anten

rotated to any position to obtain the best performance. If the 

erected vertically, the transmission line should be brought ou

tally from the antenna for a distance equal to at least one-

antenna’s length before it is dropped down to the radio set. 

WOODEN 

MAST QUARTERWAVE

QUARTERWAVE

GROU ND S

INSULATORS

Figure O-6. Half-Wave Doublet Antenna.
A similar arrangement for a short, center-fed half-wave an

shown in figure O-8. The ends of this antenna are connected to a 

dry wood, such as a bamboo pole, and the bend in the pole h

antenna wire straight. Another pole, or bundle of poles, serve

mast. 

Figure O-9 shows an improvised vertical half-wave antenna. T

nique is used primarily with FM radios. It is effective in heavily 

VERTICALLY

POLARIZED

HORIZONTALLY

POLARIZED

INSULATORS

QUARTERWAVE

TRANSMISSION

LINE

A B

Figure O-7. Center-Fed Half-Wave Antenna.

BAMBOO POLES

LASHING

WIRE

1 TURN LOOP

1 TURN LOOP

QUARTERWAVE

QUARTERWAVE

Figure O-8. Bent Bamboo Antenna. 
areas to increase the range of portable radios. The top guy w

connected to a limb or passed over the limb and connected 

trunk or a stake. 

HIGH FREQUENCY, FIELD EXPEDIENT DIRECTIO

ANTENNAS 

The vertical half-rhombic antenna (fig. O-10 on page O-1

long-wire antenna (fig. O-11 on page O-12) are two field 

GROUND 

STAKE

GROUND 

STAKE

INSULATO R

INSULATO R

INSULATO R

INSULATO R

ANTENNA WIR E

ANTENNA

 W IRE

Figure O-9. Improvised Vertical Half-Wave Antenn
directional antennas. These antennas consist of a single wire, pr

two or more wavelengths long, supported on poles at a height 

meters (10 to 20 feet) above the ground. The antennas will, h

operate satisfactorily as low as 1 meter (approximately 3 feet) a

ground. The far end of the wire is connected to ground through 

ductive resistor of 500 to 600 ohms. Use a resistor rated at least 

the wattage output of the transmitter to ensure the resistor is no

out by the output power of the transmitter. A reasonably good 

such as a number of ground rods or a counterpoise, should be 

both ends of the antenna. The radiation pattern is directional. Th

nas are used primarily for either transmitting or receiving high fr

signals. 

Figure O-10. Vertical Half-Rhombic Antenna.

RESISTOR

RESISTOR

Figure O-11. Long-Wire Antenna.
The Vee antenna is another field expedient, directional anten

sists of two wires forming a Vee with the open area of the Ve

toward the desired direction of transmission or reception (see 

To make construction easier, the legs may slope downwar

apex of the Vee (this is called a sloping Vee antenna [see fi

page O-14]). 

The angle between the legs varies with the length of the legs 

achieve maximum performance. 

When the antenna is used with more than one frequency or w

use an apex angle that is midway between the extreme an

mined by the chart.

To make the antenna radiate in only one direction, add nonind

minating resistors from the end of each leg (not at the apex) 

Figure O-12. Vee Antenna.

INSULATORS

10’

10’

10’
The resistors should be approximately 500 ohms and have a po

ing at least one-half that of the output power of the transmitt

used. Without the resistors, the antenna radiates bidirectiona

front and back. 

The antenna must be fed by a balanced transmission line. 

Figure O-13. Sloping Vee Antennas.

INSULATORS

INSULATO

RESISTORS

RESISTOR
Use table O-1 to determine the angle and the length of the leg

Table O-1. Leg Length for Vee Antennas.

Antenna 

Length 

(Wavelength)

Optimum 

Apex Angle 

(Degrees)

1 90

2 70

3 58

4 50

6 40

8 35

10 33

(reve
Appendix P

Radio Operator’s Checklist

Before you operate any radio set, get the appropriate equipment technical manual (TM) and carefully study the operating instructions. Refer to

the panel diagrams, connections diagrams, and the paragraphs covering

the description of components during the preliminary starting procedure.

Make sure that the proper cables are connected to the proper panel connectors, and that the controls are correctly set. Even the most experienced operators should check their preliminary procedures against the

TM references from time to time to insure accuracy and avoid damaging

the equipment. Use the operational checklist and the equipment performance checklist to determine what to do to remedy any problems

encountered during starting procedures and operation. 

STEPS IN OPERATING RADIO SETS 

Radio sets issued to a unit vary in type according to the communications

requirements of the unit. For example, some sets may be completely

contained in one assembly, while others may consist of separate components that must be properly connected to assemble a complete radio set.

The following steps are generally required in operating a radio set. 

Check the Set for Completeness 

Make sure that all the necessary components and accessories are on hand

and ready for use. Refer to the equipment basic issue items list in the

TM. Never operate the transmitter without the antenna attached. 

Inspect the Condition of the Knobs, Dials, Switches, and 

Controls 

Look for knobs, dials, switches, and controls that are loose on their

shafts, bind when being operated, won’t operate, or are damaged in any

other way. Make corrections where possible or report the faulty
P-2 _______________________________________________ MCRP 3-40.3B

condition to the CIS officer or CIS chief. Make sure that all knobs and

exterior parts are on the set. Immediately report any that are missing. 

Check the Condition of Plugs, Receptacles, and Connectors 

Do not attempt to connect the set for operation until you are sure that the

plugs and connectors are clean and in good condition, and the receptacles to which they must be connected are also clean and in good condition. 

Check the Connections Diagrams 

The connections diagrams in the equipment TM show the type and number of cables required to interconnect the components of the radio set for

each type of operation. The radio set may be damaged if cables are connected to the wrong receptacles. 

If the connectors don’t match, it is possible to physically damage the

pins or sleeves of the connector. 

If a cable is connected to a receptacle into which it fits but does not

belong, it may cause serious electrical damage to the equipment and, in

some cases, injury to the operator. 

Make Sure of Dial, Switch, and Control Settings 

Some radio sets can be seriously damaged if the switches, dials, and controls are not set to the required initial settings before applying power or

making the initial timing adjustments. Before applying power, check the

equipment TM to be sure you performed all preliminary starting procedures. Be sure radios installed in vehicles are turned off before starting

the vehicle’s engine to avoid damage to radio equipment. 

Follow the Starting Procedure 

The equipment TM covers, in detail, the proper procedure for starting

the radio set. If there is a specific sequence for starting the set, it is

described in the manual. Perform the operations in the proper sequence.
Radio Operator’s Handbook ______________________________ P-3

Apply Power 

After the proper connections are made, and all switches are properly set,

power may be applied to the set. 

Allow the Set to Warm Up 

Radio sets usually require a warm-up period when first applying power

in order to stabilize the equipment. In some cases, it is possible to damage a set by attempting to operate a set without allowing a warm-up

period. Most sets are protected against such damage, but it is foolish to

risk damage to a radio set by trying to put it on the air before it is ready. 

Tune to the Desired Frequency (Channel) 

Tune the transmitter to the frequency of the desired channel according to

the procedures in the equipment TM. Use the methods that are given in

the TM to check for correct tuning. 

Check the Set for Normal Operation 

While the set is in operation, check the indicators frequently to be sure

that the set is operating correctly. If anything unusual occurs during

operation, investigate it immediately. When necessary, turn off the

power to the set and refer to the operational checklist and the equipment

performance checklist in the equipment manual. If the corrections given

in the operational checklist and the equipment performance checklist

will not correct the trouble, report the condition to the unit electronics

maintenance shop. Make sure that the condition of the set and the action

taken are properly recorded on the maintenance records. 

Use the Proper Procedure to Turn Off the Set 

After operation (or if the set is being turned off because of improper

operation) make sure that the controls, switches, and dials are properly

set (this may not be required on some radios). Proceed to shut down the

components of the set in the sequence specified in the equipment manual. Simple radios may require nothing more than turning the power
P-4 _______________________________________________ MCRP 3-40.3B

switch to its OFF position, but more complex sets may require elaborate

shutdown procedures. 

Operating Hints

Use a handset or headset, rather than a loudspeaker, if the incoming signal is weak. Make sure that the microphone or handset is in good condition. Speak directly into the microphone; speak slowly and distinctly. 

Make sure that the vehicle’s battery voltage (if radio set is vehicularmounted) is within the correct range. Keep the engine running to charge

the battery. Move the set or the vehicle, if necessary, to improve reception. 

Lack of communications or poor communications may be caused by—

l Too great a distance between radio sets. 

l Poor choice of location (siting) at one or both ends of the circuit. 

l Terrain—hills or mountains. 

l Noise and interference. 

l Not enough transmitter power. 

l Defective equipment. 

l Improper adjustment of equipment. 

l Ineffective antenna. 

l Improper frequency assignment.

Poorly maintained equipment and improper operation can be just as

effective in preventing communications as excessive distance or mountainous terrain. To avoid problems, observe the following precautions at

all times: 

l Study the TMs for the equipment you are using. They provide complete operating instructions and maintenance procedures. 

l Keep your radio set clean and dry. 

l Handle your radio set carefully.
Appendix Q

Glossary

Section I. Acronyms

AC................................................................................ alternat

AF ....................................................................................audio 

AM ......................................................................... amplitude m

ASAP .......................................................................... as soon 

ASIP.........................................advanced systems improveme

bps......................................................................................bits 

C4I ............................... command, control, communications, 

and i

CDT ...................................................................... Central Day

CEOI. ......................... communications-electronics operating 

CEP ................................................................circular error of 

CIS ..........................................communications and informati

cm.............................................................................................

COMINT..................................................... communications i

COMSEC .......................................................... communicatio

CONUS............................................................. continental Un

COTS ...............................................commercial off-the-shelf 

CST ....................................................................... Central Stan

DACT...................................... data automated communicatio

DAMA ..................................................demand assigned mult

db .............................................................................................

DC........................................................................................ dir

DCT .......................................................digital communicatio

dm ............................................................................................

dkm ..........................................................................................

DMS......................................................................digital mess
DTE.....................................................................data terminal eq

DTG ................................................................................. date-tim

EA ................................................................................... electron

EDT....................................................................... Eastern Daylig

EEFI ........................................essential elements of friendly info

EMCON .......................................................................... emission 

EMP ........................................................................electromagne

EP..............................................................................electronic pr

EPLRS ................................enhanced position location reportin

ES.....................................................................electronic warfare 

EST ....................................................................... Eastern Standa

EW ................................................................................electronic 

FAC ......................................................................... forward air c

FLOT ..............................................................forward line of ow

FM.......................................................................... frequency mo

FMF ............................................................................Fleet Mari

FMFM............................................................ Fleet Marine Force 

GHz.............................................................................................g

GPS .................................................................. global positionin

HF ..................................................................................... high fr

Hz.................................................................................................

hm ............................................................................................he

ID ......................................................................................... ident

IED................................................... imitative electromagnetic d

IR .................................................................................................

JC2WC................................Joint Command and Control Warfar

JSC .........................................................................Joint Spectrum 

KHz............................................................................................. k

km .............................................................................................. k

kbps...........................................................................kilobytes pe

kW................................................................................................ 
LOS........................................................................................ l

LSB .................................................................................. lowe

LUF.....................................................................lowest usable 

m ..............................................................................................

MAGTF ...................................................... Marine air-ground 

MCRP ...............................................Marine Corps reference 

MCWP ..........................................Marine Corps warfighting 

MDT...................................................................Mountain Day

MEU(SOC) ........ Marine expeditionary unit (special operation

MFP ..........................................................moisture funguspro

MHz .........................................................................................

mi .............................................................................................

MIJI.................................... meaconing, intrusion, jamming, i

mm ...........................................................................................

MPF ...........................................................maritime prepositio

MST .................................................................. Mountain Stan

MUF............................................................. .maximum usable 

MUX ........................................................................................

NBC ......................................................nuclear, biological, an

NCS...............................................................................net con

NVIS ...................................................... near vertical incidenc

ohm ......................a unit of electrical resistance (named for G

OTH ................................................................................ over t

prosign ............................................................................... prec

proword............................................................................ proc

PDT........................................................................ Pacific Day

PLRS................................................... position location report

PST.........................................................................Pacific Stan

RCU ............................................................................remote c

RDF..........................................................................radio direc

RF..................................................................................... radio 

RFI ............................................................... radio frequency i

SAA .............................................................satellite access au

SATCOM ...........................................................satellite comm
SBB............................................................................. switched b

SCR........................................................................... single chan

SCSI ....................................................small computer systems in

SHF ......................................................................... super-high fr

SID .......................................................... sudden ionospheric dis

SINCGARS................. single-channel ground and airborne radi

SIP............................................................ systems improvement 

SOP .............................................................standing operating p

SPEED ...................system planning, engineering, and evaluatio

SSB ..................................................................................single s

SWR...........................................................................standing-w

TACSAT............................................................................tactical 

TAMCN ...............................table of authorized materiel control 

TCIM ......................................tactical communications interface 

TDN ......................................................................... tactical data 

TEMPEST................... an unclassified name referring to the me

to ensure computer 

TM ................................................................................. technica

TOD ........................................................................................ tim

TRANSEC ...............................................................transmission 

TWA................................................................................ tilt whip 

UHF ........................................................................... ultrahigh fr

USB.................................................................................. upper s

UTC .............................................................Coordinated Univer

UTM........................................................... universal transverse m

UV............................................................................................. ul

VHF .......................................................................... very high fr

WBA ............................................................................ whip-base 

WLC...............................................................................whip loa

WWA ........................................................................whip to wire 

yd .................................................................................................
Section II. Definitions

A

amplitude modulation (AM). Modulation in which the ampl

carrier wave is varied above and below its normal value in 

with the intelligence of the signal being transmitted.

analog. A continuously variable signal which conveys info

the change of the value or magnitude of the signal. The 

change in either amplitude, phase, frequency, or duration.

antenna gain. The effectiveness of a directional antenna as c

a standard nondirection antenna. It is usually expressed as t

decibels of standard antenna input power to directional ant

power that will produce the same field strength in the desired 

For a receiving antenna, the ratio of signal power values prod

receiver input terminals is used. The more directional an ante

higher is its gain.

authentication. A security measure designed to protect a co

tions system against acceptance of a fraudulent transmissions 

tion by establishing the validity of a transmission, m

originator.

B

baseband. In a carrier (or subcarrier) wire or radio transmissi

the band of frequencies occupied by the signal before it mo

carrier (or subcarrier) frequency to form the transmitted or rad

black. The black designation is applied to all wire lines and 

within a terminal or switching facility which handle encrypted 

brevity code. A code which provides no security but which 

sole purpose the shortening of messages rather than the conc

their content.
bulk encryption. An application of on-line cryptographic op

where the encryption and decryption process is performed at de

points of technical interface within a communications system; in

put signals from various subscriber terminals thereby being 

graphically processed at these points. The operation is perfo

bulk; i.e., two or more channels processed simultaneously by on

security device.

C

call sign. Any combination of characters or pronounceable word

identifies a communication facility, a command, an authority, an 

or a unit; used primarily for establishing and maintaining com

tions.

carrier. (1) The radio wave produced by a transmitter when th

modulating signal, or any other wave, recurring series of pulses, 

current capable of being modulated. Also called carrier wav

wave generated locally at a receiver that, when combined with 

bands of a suppressed carrier transmission and a suitable detec

duces the modulating wave.

communications security (COMSEC). The protection resulti

all measures designed to deny unauthorized persons inform

value which might be derived from the possession and study of 

munications, or to mislead unauthorized persons in their interpre

the results of such possession and study. Communications 

includes cryptosecurity, transmission security, emission secur

physical security of communications security materials and info

critical frequency. The highest frequency at which a given wav

given time will, if transmitted vertically, be refracted back to ea

layer of the ionosphere.

cryptography. The art or science which pertains to the variou

and methods for rendering plain text unintelligible, and reco

unintelligible texts into intelligible language; application of tha

by means other than cryptanalysis.
D

data. Representation of facts, concepts, or instructions in a 

manner suitable for communication, interpretation, or pro

humans or by automatic means. Any representations such as 

or analog quantities to which meaning is or might be assigned

date-time group (DTG). The date and time, expressed in 

zone suffix, the message was prepared for transmission. (Ex

six digits followed by the zone suffix; first pair of digits denot

second pair the hours, third pair the minutes.)

decibel (dB). A unit used to express the magnitude of a chang

or sound level. A change of three decibels is the change in pow

a pure sine wave that is just barely detectable by the human e

ference in decibels between two signals is 10 times the com

rithm of their ratio of powers or 20 times the common logarit

ratio of voltages or currents. One decibel is one-tenth of a bel

digital. A signal having discrete states, usually two, such as th

or absence of a voltage. The signal is given meaning by 

numerical values or other information to the various possible 

tions of the discrete states of the signal.

directed net. A net in which no station other than the net con

can communicate with any other station, except for the trans

urgent messages, without first obtaining the permission of the 

station.

E

electromagnetic radiation. Radiation made up of oscillati

and magnetic fields and propagated with the speed of light.

electronic warfare (EW). Any military action involving the u

tromagnetic and directed energy to control the electromagneti

or to attack the enemy. The three major subdivisions within 
warfare are: electronic attack, electronic protection, and electro

port measures.

F

free net. A net in which any station may communicate with a

station in the same net without first obtaining permission from 

control station to do so.

frequency. The number of complete cycles per unit of time fo

odic quantity such as alternating current, sound waves, or v

objects. Frequency is expressed in hertz, kilohertz, megahertz, a

hertz. 

frequency band. A continuous range of frequencies extending 

two limiting frequencies.

Frequency hopping. A method of jumping from frequency to fr

in synchronization with one another in a random order at a rate 

100 times per second. Frequency hopping is the preferred m

communication with SINCGARS radios. 

frequency modulation (FM). Frequency modulation is the pr

varying the frequency (rather than the amplitude) of the carrier 

accordance with the variations of the modulating signals. The am

or power of the FM carrier does not vary during modulation

quency modulation system is practically immune to atmosph

man-made interference.

frequency spectrum designation. VLF (very low frequency): b

kHz (0.03 MHz). LF (low frequency): 30-300 kHz (0.03-0.3 M

(medium frequency): 300-3000 kHz (0.3-3 MHz). HF (high fre

3-30 MHz. VHF (very high frequency): 30-300 MHz. UHF (u

frequency): 300-3000 MHz. SHF (super high frequency): 3000

MHz (3-30 GHz). EHF (extremely high frequency): 30-300 GH
G

ground wave. A radio wave that is propagated over the earth 

narily affected by the presence of the ground and the tropos

ground wave includes all of the components of a radio wav

earth except ionospheric and tropospheric waves. The groun

refracted because of variations in the dielectric constant of 

sphere, including the condition known as a surface duct.

guard. To maintain a continuous receiver watch with transm

for immediate use. A complete log is to be kept.

H

half-duplex—Refers to a mode of transmission in which co

tion between two terminals occurs in either direction, but i

direction at a time. This is the typical mode of operation for t

gle-channel radios. 

hertz (Hz). A unit of frequency equal to one cycle per second

I

imitative communication deception (ICD). The introductio

tion into enemy systems which imitate the enemy’s emissions

in the clear. In plain text. When cryptographic devices are n

protect a transmitted signal.

ionosphere. A region in the earth’s outer atmosphere wher

electrons are present in quantities sufficient to affect the prop

HF radio waves. It begins about 30 miles above the earth a

above 250 miles, with the height depending on the season of y

time of day. The chief layers of the ionosphere and their ap

heights are: 

D layer—30 to 60 miles

E layer—60 to 90 miles

F layer—90 to 250 miles
J

jamming (electromagnetic). The deliberate radiation, reradia

reflection of electromagnetic energy for the purpose of preve

reducing an enemy’s effective use of the electromagnetic spectr

with the intent of degrading or neutralizing the enemy’s combat 

ity.

L

line of sight (LOS). The straight unobstructed path between two 

link. In communications, a general term used to indicate the exis

communications facilities between two points.

log. A chronological record of station events.

N

needline. A requirement to establish communications between t

or agencies.

net (communications). An organization of stations capable o

communications on a common channel or frequency.

net call sign. A call sign which represents all stations within a n

net control station. A communications station designated to 

traffic and enforce circuit discipline within a given net. Also call

O

obstacle gain. The increase in signal strength obtained over a lo

communications path where a mountain obstacle or range of 

located about halfway between transmitting and receiving antenn

obstacle gain offsets some of the path losses normally expected.
operating signals. Three letter groups used as necessary in c

with operations or communications to convey orders, in

requests, reports, and information to facilitate communication

P

precedence. In communications, a designation assigned to a m

the originator to indicate to communications personnel the rel

of handling and to the addressee the order in which the messa

noted.

procedure sign (prosign). One or more letters or characters

nation thereof, used to facilitate communications by conveyin

densed standard form certain frequently used orders, in

requests, and information related to communications.

procedure word (proword). A word or phrase limited to 

phone procedure used to facilitate communication by conve

mation in a condensed standard form. 

Propagation. A phenomenon by which any wave moves from 

to another.

pulse code modulation (PCM). The form of modulation in 

modulating signal is sampled, and the sample quantitized an

that each element or information consists of different kinds a

bers of pulses and spaces.

pulse position modulation (PPM). A form of pulse mod

which intelligence is conveyed by varying the time interva

successive pulses are displayed from their normal times of oc

push to talk operation. Voice communications on a circuit in 

tion at a time in which operation of a switch is required prior 

ing transmission.
R

radio frequency (RF). A frequency in which coherent electrom

radiation of energy is useful for communications purposes. Th

range is from approximately 10 kilohertz to 100,000 megahertz.

radio silence. A condition in which all or certain radio equipme

ble of radiation is kept inoperative. (In combined or U.S. joint 

Service communications the frequency bands and/or types of eq

affected will be specified.)

red. Designation applied to transmission lines, equipment, syste

or areas passing unencrypted signals.

S

satellite communications. Use of communication satellites, 

reflecting belts of dipoles or needles, or reflecting orbiting bal

extend the range of radio communications by returning signals 

from the orbiting objective, with or without amplification.

simplex. Refers to a mode of operation in which commu

between two terminals can take place in only one direction.

skip distance. The minimum separation at which radio wave

specified frequency can be transmitted at a specific time betw

points on the earth by reflection from the regular ionized laye

ionosphere.

skip zone. A region, in relation to a given transmitter, in which n

would be predicted, either due to direct repetition or due to r

waves.

sky wave. A radio wave that reaches the receiving location afte

tion from the ionosphere.
T

tactical radio net. A functional radio net used by a comm

immediate and direct control of the fire and maneuver or mo

his subordinate units.

traffic. All transmitted and received messages.

transceiver. A radio transmitter and receiver combined in on

having switching arrangements such as to permit use of one o

cuit components for both transmitting and receiving.

transducer. A device that transfers or changes one type of e

another form. An example is a loudspeaker, which change

energy into acoustic (mechanical) energy.

(reve
Appendix R

References and Related 

Publications

Joint Publication (Joint Pub)

1-02 Department of Defense Dictionary of Military 

Associated Terms

Marine Corps Doctrinal Publication (MCDP)

6 Command and Control

Marine Corps Warfighting Publications (MCWPs)

6-2 MAGTF Command and Control Operations (u

 development)

6-22 Communications and Information Systems

Marine Corps Reference Publications (MCRPs)

6-22A TALK II-SINCGARS Multiservice Communic

Procedures for the Single-Channel Ground 

and Airborne Radio System

6-22B Multiservice Procedures for Spectrum Manage

in a Joint Environment

6-22D Antenna Handbook (under development)

Army Field Manuals (FMs)

11-32 Combat Net Radio Operations

24-11 Tactical Satellite Communications

24-18 Tactical Single-Channel Radio Communication

Techniques

24-19 Radio Operator’s Handbook

(reve