Art

jBoulder laboratories

PB 151404

"Ho. 45

OPERATING INSTRUCTIONS

FOR

ARN-2 AUXILIARY LOG-LINEAR NOISE RECORDER

BY R. T. DISNEY AND C. A. SAMSON

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
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NATIONAL BUREAU OF STANDARDS

technical <Vtote

45

January, I960

OPERATING INSTRUCTIONS FOR THE ARN-2 AUXILIARY

LOG-LINEAR NOISE RECORDER

by

R. T. Disney and C. A. Samson

NBS Technical Notes are designed to supplement the Bureau's regular publications program. They provide a means for making available scientific data that are of transient or limited interest. Technical Notes may be

listed or referred to in the open literature. They are for sale by the Office of Technical Services, U. S. Department of Commerce, Washington 25, D. C.

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UNITED STATES DEPARTMENT OF COMMERCE

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Price $ »50

OPERATING INSTRUCTIONS FOR THE ARN-2 AUXILIARY

LOG-LINEAR RECORDER

R. T. Disney and C. A. Samson

National Bureau of Standards

Boulder, Colorado

Table of Contents

Page

1. Purpose 1 1. 1 General 1 1.2 Choice of Parameters 1 1. 3 The Measured Values 1 2. General Operation 2

2. 1 Block Diagram 2

2. 2 Function of Units 2

3. Operational Procedures 3

3. 1 General 3

3. 2 Checks and Adjustments 3

3. 2. 1 Power Supplies 3

3.2.2 Detector Meter 3

3.2.3 I. F. Amplifier 3

3.2.4 Detector 4

3.2.5 Log Linear Amplifier Integrator 5

3. 2. 6 Recording Meters 5

3. 2. 7 Calibration with Respect to the Power Recorder. 7

3. 3 Recording 8

4. Daily Operational Checks and Calibration 8

4. 1 General 8

4. 2 Power Supplies . 9

4.3 Detector Meter 9

4.4 First Daily Calibration 9

4. 5 Completion of Daily Log Sheet . 9

4.6 Second Daily Calibration 10

4.7 Recording 10

5. Miscellaneous Information 10

5. 1 Connection to A or B Rack 10

5.2 Stamping the Record 11

5.3 Chart Drive Time Setting 11

5.4 Tube Checks 12

5. 5 Detector Meter Scales 12

5. 6 Log-Gate Timer Setting 12
Table of Contents (cont'd)

Page

6. Records Processing of Log and Voltage 13

6. 1 General 13

6. Z Editing before Scaling , 13

6.3 Scaling 13

6.4 Editing after Scaling 14

6.5 Analysis of the Records 14

6.6 Disposition of Data 15

7. Table of Contents 15
Operating Instructions for the ARN-2 Auxiliary

Log-Linear Noise Recorder

R. T. Disney and C. A. Samson

1. Purpose

1. 1 General

1 The auxiliary equipment for the ARN-2 recorder installed in

the C rack is for the purpose of measuring the deviation of the average

voltage and the average logarithm of the voltage with respect to the

average power. The reason for measuring these additional parameters of the noise is to determine to a much greater extent the

interference value of the recorded noise to a number of types of

communication systems. By measuring the average value of the three

parameters, it is possible to reconstruct the average amplitudeprobability distribution required to give the values recorded . From

this distribution, considerable information can be derived as to the

performance of a particular communication system in the presence of

3 noise .

1.2 Choice of Parameters

The average voltage and average logarithm of the voltage were

chosen as the parameters to be measured for a number of reasons.

First, it was thought highly desirable to use a parameter of the noise

envelope that could be described easily and simply mathematically.

The power (V ), the voltage (V), and the log of the voltage (log V) fell

nicely into this classification, and discarded such parameters as peak

or quasi-peak values. The next consideration was to use three parameters that could be represented by fairly well separated points on the

amplitude -probability plot. The power is influenced most by the high

voltage, low-probability values, while the log is influenced most by the

low voltage, high-probability values . The voltage value falls approximately midway between the other two values. The third factor

considered was the ease of obtaining the values from a circuitry standpoint. The voltage required only an averaging and metering circuit

while the log required a logarithmic amplifier, averaging and metering

circuit. All of this is rather straightforward circuitwise.

1. 3 The Measured Values

The actual measurements made are deviations of the average

voltage and average log in db below the power. The reason for making

the deviation measurement was twofold. First, the deviation could be
- 2 -

measured directly more accurately than measuring, for instance, the

power and voltage independently and comparing the two. Second, the

dynamic range of any system used to measure any characteristic of

radio noise must necessarily be large. The ARN-2 power recorder

was already in successful operation providing a constant power level

take off point in the servo loop. Therefore, the required dynamic

range of the voltage and log measuring circuitry could be reduced so

the average values would fall within a 20 to 30 db range.

2. General Operation

2. 1 Block Diagram

The signal is taken through an isolation resistor just prior to

the input to the parabolic amplifier in the servo loop of the power

recorder. This signal voltage is fed into the input of another 51 kc

1. F. amplifier (see block diagram, Fig. 1). The output is connected

to the input of a 51 kc amplifier-detector. The output of the detector

is connected to the inputs of the log and linear amplifiers, integrators,

and metering circuits. These outputs are connected to recording

meters through the log -gate timer to record directly in db below the

power.

2. 2 Function of Units

The I. F. amplifier and detector are quite similar to the

corresponding units in the power recorder. The log-linear amplifierintegrator is a two channel integrator with separate inputs for each

channel from the detector. The log input is at the detector output level

and the linear input is 30 db below the log input. The log signal is

connected to a logarithmic amplifier. The output of this amplifier is

averaged by an R-C integrating network with a time constant of about

thirty seconds and recorded. The linear signal is averaged using an

R-C integrating circuit with a time constant of approximately fifty

seconds. The averaged signal is fed into a d. c. amplifier, then into a

logarithmic amplifier, and then into another d. c. amplifier which

drives the recorder. The function of the log-gate timer is to prevent

the log and linear recorders from recording a nonvalid reading with

respect to the power reading. If the average power at the output of the

detector is one db from the reference point, the integrator -control unit

will require 200 to 240 seconds to step the attenuator. Therefore, if a

period of four minutes elapses from the time of the last attenuator

step, the power reading must be within 1 db of the true power reading,

and valid log and linear readings may be obtained with respect to the

power reading. The log-gate timer insures that this necessary fourminute interval has passed from the time of the last attenuator step

before the log and linear readings are displayed on the recording
- 3 -

meters. The log-gate timer also drives the recorder pens to the

right-hand side of the charts during the three-minute period when the

attenuator forward drive is connected just after a frequency change.

3. Operational Procedures

3. 1 General

By means of the daily checks and adjustments, the correct

operation of the C rack independent of the power recorder is assured

and the calibration insures the correct operation in conjunction with

the power recorder.

3. 2 Checks and Adjustments

The following steps should be taken to insure the proper

functioning of the C rack itself.

3.Z. 1 Power Supplies - Check the panel meters indicating the output voltage of the power supplies to insure the proper supply voltages.

If the output meter for the 75 volt supply does not indicate 75 volts

+ 1 volt, open the drawer and adjust VOLT ADJ on the 75 volt power

supply chassis (see Fig. 2) so that the meter reads exactly 75 volts.

Next check the output meter for the 300 volt supply, and if it does not

read 300 volts + 5 volts, adjust VDC ADJ on the top of the 300 volt

supply chassis so that the 300 volt reading is obtained.

3.2.2 Detector Meter - All checks on the equipment are made in

reference to the detector meter reference point (0 db on the meter with

the meter selector switch in the db position). Therefore, the first

step in checking the operation of the equipment is to adjust the meter

controls to give the proper meter reading. To accomplish this, turn

the meter selector switch to the ZERO position. The meter should

now read at meter ZERO, the last line on the left-hand side of the

meter scale. If the meter does not read meter ZERO, open the drawer

and adjust the ZERO ADJUST (R 39) located on the detector chassis

(see Fig. 3). Next turn the meter selector switch to REF. The

detector meter should now read db. If it does not, adjust the RANGE

ADJUST (R 44) located on the detector chassis. Recheck the meter

ZERO, and if this requires readjustment recheck the REF adjustment,

since there is some interaction between the two controls.

3.2.3 I. F. Amplifier - (A word of caution is advisable at this time.

The detector reference voltage is 300 volts. During the switching

operation of the power recorder, a relay (Re 1) on the detector chassis

is energized by the muting voltage from the power recorder. This
- 4 -

relay switches the detector output to the 300 volt supply giving and

maintaining the reference reading for the period (90 to 180 seconds)

that the cam operated switch in the E-A power recorder is closed. No

adjustments utilizing the detector meter or the log-linear recording

meters should be made during this period). With minimum output on

51 kc, connect the output of the alignment oscillator directly to the

input, 1 1, on the I. F. amplifier chassis. The gain control (R8) of the

I. F. amplifier should be set so that an input from the alignment

oscillator of approximately 65 db will give the detector reference output (0 db on the scale). This adjustment is not critical at this time.

The exact setting is explained in paragraph 3. 2. 7. Now tune C 1 for

maximum reading on the detector meter. When the tuning of any

capacitor on the ARN-2 is found to give a peak reading with the adjust-*

ment screwdriver slot either parallel or perpendicular to the control

mounting screws, a check should be made to be sure a double peak is

obtained since in one position or the other, the capacitor will be at

maximum or minimum capacitance position.

3.2.4 Detector - With the output of the alignment oscillator still

connected to the input of the I. F. amplifier, adjust C2 on the detector

chassis for maximum detector meter reading. Next adjust the detector

bias. To do this, disconnect the input to the I. F. amplifier. Turn the

detector meter switch to the 60 db position. Adjust the BIAS (R 14)

control on the detector chassis to obtain approximately db reading on

the detector meter. This adjustment affects the detector linearity and

it may be necessary to readjust later to improve the linearity at low

detector output. Turn the detector meter switch back to the db

position and reconnect the alignment oscillator to the I. F. amplifier

input. Adjust the output of the alignment oscillator so that detector

Odb reference is read on the detector meter. The detector should be

linear, within + 1 db, over a range of 60 db, (from 10 db above

reference to 50~db below reference). To check the linearity, increase

the alignment oscillator output by 10 db. The detector meter should

now read + 10 db. Decrease the alignment oscillator by 20 db, and

change the detector meter selector switch to the 20 db position. The

reading at this point should be -10 db (20 db below reference on the

switch position +10 db meter reading = -10 db). Continue to

decrease the alignment oscillator in 10 db steps and check the detector

meter reading (with the detector meter switch in the appropriate

position) until a reading of -50 db has been obtained (60 db below

reference on the switch position +10 db meter reading = -50 db). The

detector meter reading should be within + 1 db at each of these steps.

If it is not within this limit at the lower input end (-30, -40, or

-50 db points) readjust the bias control to bring the reading within the

acceptable limits. If it is not within limits at the + 10 db point, try
- 5 -

replacing the 3A2 diode or checking the other tubes on the detector

chassis.

3.2. 5 Log Linear Amplifier Integrator - The d.c. amplifier

balance should be checked and reset if necessary. To check the

balance, turn the BAL- LONG -SHORT switch to the BAL position.

Then turn the meter switch to the BAL position. The detector meter

should now read at meter zero (the last line on the left-hand side of

the meter scale). If the meter reads far enough below the meter zero

so that the meter hand rests on the stop or if the meter reads above

-6 on the meter scale, open the drawer and adjust the AMPLIFIER

BALANCE (R33) control so that the meter reads meter zero. Return

the meter control to ZERO and the BAL-LONG-SHORT switch to

SHORT.

If required, the d. c. amplifier linearity may be checked in the

following manner, though normally it is not necessary to do so. Originally the test point, TP 1, on the detector chassis was connected

to the log tap on the detector output divider network. In most cases, it

has been connected to the linear tap on the output divider network. This

can be checked with the VTVM. With the input to the I. F. amplifier

from the alignment oscillator adjusted to give reference detector meter

reading, the voltage at TP 1 on the detector chassis should be 300 volts

if TP 1 is connected to the log output tap or 10 volts if connected to the

linear tap. If with the detector meter indicating reference, the voltage

at TP 1 is approximately 10 volts this point may be used to check the

d. c. amplifier linearity. If the voltage at this point varies more than

two volts from the 10 volt value, the detector unit should be replaced.

Set the alignment oscillator output so that exactly 10 volts is measured

at TP 1 on the detector chassis. Now check the voltage at TP 1 on the

amplifier~integrator chassis. There should be a 10:1 gain through the

d. c. amplifier so that a reading of 100 volts should be obtained at TP 1 on the amplifier -integrator chassis. The output of the alignment

oscillator should now be decreased so that the input to the d. c. amplifier (measured at TP 1 on the detector chassis) is decreased in 1 volt

steps down to 1 volt. The corresponding values of the output of the

d.c. amplifier should be ten times the input, that is 100, 90, 80, etc.

to 10 volts as measured at TP 1 on the amplifier-integrator chassis. If this varies by more than 10% of the correct value, the d.c. amplifier

tubes should be checked and replaced if necessary or if this does not

correct the linearity, the amplifier -integrator unit should be replaced.

3.2. 6 Recording Meters - First set the mechanical zero of both

recorders. To do this, disconnect the input to the recorders by

disconnecting the Cannon connector on the back of the recorder.
- 6 -

Adjust the mechanical zero adjustment (see Fig. 4) so that the

recording pens are marking on the first line on the left -hand side of

the chart paper. Reconnect the Cannon connector. To make the scale

adjustments, adjust the signal input to the I. F. amplifier from the

alignment oscillator so as to give detector reference reading on the

detector meter. Both recording pens should now be on the db lines

(the first line on the left-hand side of the chart paper). The chart

paper used should be E-A No. 4304 (sixty divisions with every fifth

line accentuated) on the log (left-hand) recorder, and 4303 (forty

divisions with every fifth line accentuated) on the linear (right-hand)

recorder. If either pen is not recording on the db line, appropriate

adjustment should be made. To correct the log recorder, adjust

RECORDER ZERO (R 15) on the amplifier-integrator chassis. To

correct the linear recorder, adjust the RECORDER ZERO (R47) on the

amplifier-integrator chassis. Next set the recorder range. Decrease

the I. F. amplifier input by 20 db by means of the alignment oscillator

output attenuator. This should give a reading of 20 db on the linear

chart (the last line on the right-hand side of the chart paper. If it does

not, correction should be made by adjusting the RECORDER RANGE

(R45) on the amplifier -integrator chassis until the linear recorder

indicates 20 db. Decrease the output of the alignment oscillator

another 10 db (total of 30 db below detector reference). The log

recorder should now read 30 db (the last line on the right-hand side of

the log chart). If it does not, correct the reading by adjusting

RECORDER RANGE (Rll) on the amplifier-integrator chassis. Return

the alignment oscillator to the output required to give detector

reference and again check the db point on the two recording meters

readjusting as above if necessary. If readjustment is necessary due to

the interaction of the ZERO and RANGE adjustments, the full range

(20 db for the linear and 30 db for the log) should be rechecked and

readjusted if necessary. If the db indication is correct on both

recording meters, the intermediate points should now be checked.

Decrease the alignment output by 10 db. Both recording meters

should now read within 0.5 db (one small chart division) of the 10 db

line (this is the fifth accented line from the left on each chart, the

accented lines being 0, 2.5, 5, 7.5, and 10 db). Decrease the alignment oscillator by another 10 db and the log and linear recorders

should indicate 20 db on the charts. If these intermediate points are

not recording correctly, appropriate remedial steps should be taken.

First recheck the db and full range settings of the recording meters.

If these are set properly, and both recorders indicate nonlinearity,

recheck the linearity of the detector (paragraph 3. 2.4). If the detector

meter indicates detector linearity within the prescribed limits but the

meter itself is suspect, the meter can be checked by measuring the

output voltage at TP 1 with the VTVM. If the detector meter and the
- 7 - VTVM agree, it can be assumed that the detector meter is correct.

However, if they disagree, it is highly recommended that a second

VTVM be used to obtain readings verifying the error in either the first

VTVM or the detector meter. If only the linear recorder is incorrect

at the intermediate points, linearity of the d.c. amplifier may be

checked (paragraph 3.2. 5). If after proper adjustment either the

detector or d.c. amplifier is found to be nonlinear, check and replace

bad tubes or if this does not correct the trouble, replace the unit.

3.2. 7 Calibration with Respect to the Power Recorder - After the

completion of the checks and adjustments indicated in paragraph 3.2. 1 through 3.2.6, the log and linear recorders within themselves are

functioning properly. At this point, it is necessary to adjust the gain

of the I.F. amplifier so that the proper relationship between the log

and linear recorders and the power recorder is established. The

log-linear recorder can be used in conjunction with either the A rack

(four lower frequencies) or the B rack (four higher frequencies) of the

power recorder. The selector switches on the front panel of the loggate timer and the I.F. amplifier-detector-amplifier integrator drawer

must both be in the appropriate position to record with the low (A rack)

or high ^B rack) power recorder (see paragraph 5. 1 for correct

connection). The A or B rack must be completely adjusted and in

proper operation prior to the time the following calibration procedure

is accomplished. The same procedure will be followed regardless of

which section of the power recorder is connected to the C rack. For

illustration purposes in this discussion, the assumption will be made

that the log-linear recorders are to be operated in conjunction with

the low (A rack) power recorder. Corresponding referenced units or

controls in the high (B rack) should be substituted when the connection

is changed to the B rack. Make sure that both the log -gate timer and

C rack input HIGH- LOW switches are in the LOW position. Make sure

the output of the C rack HIGH -LOW switch is connected to the input

terminal of the I.F. amplifier. Turn the BAL- LONG -SHORT switch to

the SHORT position and the log-gate timer IN-OUT switch to the OUT

position. On the A rack, connect the output of the alignment oscillator

to the dummy input terminal. Make sure the dummy antenna, channel

frequency, and alignment oscillator frequency are all on the same

frequency (it may be any one of the four low-frequency channels).

Place the STEP-MAN-AUTO channel switch in the MAN position and

the integrator switch in the REFERENCE LONG or SHORT position.

Set the A rack attenuator at 50 db and the detector meter switch

(A rack) at db. Adjust the alignment oscillator output so that the

A rack detector meter indicates detector reference (0 db on the db scale).
- 8 -

Turn the C rack detector meter switch to the db scale position. The

C rack detector meter should now read reference (0 db on the db

scale). If it does not read detector reference, open the drawer and

adjust the I. F. amplifier gain control (R8) so that the db reading is

obtained. Check the log and linear recording meters to determine that

they are reading on the db lines (if they are not, repeat the steps for

setting the recorder zero and range given in paragraph 3.2.6). If both

recording meters are indicating db, mark this point as (see

Figs. 13 and 14). Decrease the input to the C rack by 10 db by

increasing the A rack attenuator setting to 60 db. Both the log and

linear recording meters should now indicate 10 db. If they do, mark

this line 10 (if not, check zero and range adjustments as given in

paragraph 3.2.6). Again decrease the input to the C rack by 10 db by

increasing the A rack attenuator to 70 db. If both the log and linear

recording meters read 20 db within 0. 5 db (one small chart division)

mark the point indicated 20. Increase the A rack attenuator setting in

steps of 2 db (72, 74, 80) and mark the indicated point at each step

on the log chart as 22, 24, ---30. If the indicated value is more than

0. 5 db below the 20 db chart line, i. e. 18 or 19, and the chart zero

and range adjustments are properly set, return the A rack attenuator

to the 60 db point (10 db reading on the log and linear recording meters)

and mark each 2 db step on both charts from this point (the chart

deflection corresponding to the 62 db setting of the A rack attenuator

should be marked 12, etc.). This crowding of the scale at the higher

end is due to the effect of noise from the I. F. in the A or B rack.

Normally distortion of the scale will take place between 20 and 30 db

when the C rack is connected to the A rack and between 10 and 20 db

when the C rack is connected to the B rack (the I. F. gain is approximately 12 db higher in the B rack).

3. 3 Recording

The C rack is now calibrated and ready to record data. To

record, turn the BAL-L.ONG-SHORT switch to LONG, turn the detector

meter switch to ZERO, turn the log-gate timer IN-OUT switch to IN

and make sure the timer clock red hand is set at four minutes. Return

all switches on the A (and/or B) rack to normal operating position.

4. Daily Operational Checks and Calibration

4. 1 General

In order to insure good, usuable data, it is necessary to

perform certain daily checks and a daily calibration. These checks

and calibration should be made in the order given, especially with

respect to resetting the I. F. gain of the A or B rack (whichever the
- 9 -

C rack is connected to) and the I. F. gain or recorder scale adjustments in the C rack.

4. 2 Power Supplies

Read and record on the daily log sheet (see Fig. 15) the output

voltage of the 75 v. and 300 v. C rack power supplies. If the output of

the 75 v. supply varies by more than + 1 volt, reset the output voltage

(paragraph 3.2. 1). If the 300 volt supply varies more than + 5 volts,

reset the output voltage (paragraph 3.2. 1).

4. 3 Detector Meter

Note and record the reading of the detector meter with the

meter switch in the ZERO and REF positions. Since it is impossible

in most instances to actually "read" the needle position on the ZERO.

give some indication of relative position. For instance if the "reading"

is between meter zero and -6 db, indicate it by > ZERO. If it is -6 or

above, the reading can be given. If it is between meter zero and the

stop at the end of the pointer travel, it can be indicated as <ZERO. If

the pointer is resting on the stop, it can be noted as PEG or STOP. If

the ZERO or REF reading is incorrect, readjust as indicated in

Paragraph 3. 2. 2.

4.4 First Daily Calibration

This step should be completed before any I. F. gain adjustments

are made on the power recorder rack connected to the log-linear

recorder and before any further adjustments or readings are taken on

the C rack. Mark the recorder scale calibration on both the log and

linear charts as indicated in paragraph 3.2. 7 but ignoring the parts

dealing with the adjustment of the I. F. gain and readjustment of the

recorder ZERO and RANGE controls.

4. 5 Completion of Daily Log Sheet

Next record (in the same way meter ZERO is recorded) the

d.c. amplifier balance reading. If it falls outside the <ZERO or -6

reading, readjust (see paragraph 3.2.5). Check the detector linearity

over the -HO to -50 db range. If the reading is outside the + 1 db

tolerance at any 10 db point, correction should be made (see

paragraph 3.2.4). Check and record the log recorder chart reading at

the and 30 db points and the linear recorder chart reading at the

and 20 db points as indicated in paragraph 3. 2. 6. If any of these four

readings are off more than l/2 db (one small chart division) the

appropriate corrections should be made. Next, turn the detector
-IOmeter switch to the REF position. Read and record the I. F. amplifier,

detector, and amplifier integrator unit currents (No. 1, 2, and 3

respectively) from the panel meter.

4. 6 Second Daily Calibration

If any adjustments were made to the ZERO ADJUST or RANGE

ADJUST recording meter controls under 4.4, or if db reference on

the A (or B) rack detector meter did not correspond to db reference

on the C rack detector meter or if any adjustment of the A (or B) rack

I. F. amplifier was necessary to correct the diode factors, a second

chart calibration should be made. All I. Ft amplifier adjustments on

the A (or B) rack or C rack should be made prior to the second

calibration and then the calibration made (paragraph 3.2.7).

4. 7 Recording

All switches should now be put back in the record position (see

paragraph 3. 2. 8).

5. Miscellaneous Information

5. 1 Connection to A or B Rack

Since the log-linear recorder will operate with either the A or

B rack but not both simultaneously, it is necessary to change back and

forth from one to the other to obtain distribution information on all

eight frequencies. So that all stations will record on the same

frequencies simultaneously, the log-linear recorder should be connected

to the A rack on the first Monday after January 1 and then switched to

the opposite rack each Monday thereafter throughout the year. Thus,

on the first, third, fifth, etc. Monday of the year, the C rack will be

connected to the A rack while on the second, fourth, sixth, etc.

Mondays of the year, the C rack will be switched over to operate with

the B rack. In this way, at least fourteen days of operation should be

obtained on each frequency each month. In changing the operation of

the C rack from the A to B rack or the B to A rack, the daily calibration of the power recorder should first be completed (except for

resetting the I. F. gain of the rack connected to the C rack). The first

daily C rack calibration should be completed (paragraph 4.4) and the

log sheet completed (paragraph 4. 5). At this point, the C rack input

switch and the log-gate timer HIGH-LOW switch should both be turned

to correct position for the following week's recording. When this is

done, the diode factors on the control frequencies (51 kc for the

A rack and 2.5 for the B rack) should be rechecked. Even though the

output of the A and B racks are connected to the C rack by an isolating
- 11 -

resistor, connecting or disconnecting the C rack can cause a change of

0. 3 to 0.7 db in the A and B racks. The I. F. gain of the A and B

racks should now be adjusted so that the same diode factor is obtained

as obtained previously during the daily calibration of the A and B racks.

Since this is merely restoring the earlier diode reading, it is not

necessary to show any changes on the chart stamp or the calibration

summary sheet. The C rack I. F. gain adjustment and chart calibration should be performed as given in paragraph 3. 2.7.

5. 2 Stamping the Record

After the daily checks and calibration have been completed, the

log and linear charts should both be stamped with the station stamp

provided for this purpose. The stamp should be placed on the chart in a position as free from data as possible in order to facilitate the

reading of both the data and the information recorded on the stamp.

After stamping, place a check in the appropriate boxes following

Ly (log deviation), V^ (voltage deviation), HF (high frequency, B rack

connection), and LF (low frequency, A rack connection). Record the

date and approximate time the calibration was made and initial in the

space after operator. On Mondays, the chart should be stamped twice.

Once when the calibration for the previous week's frequencies has been

completed and again after the final calibration of the day for the

frequencies to be used during the following week. In this way, the time

recorded on the stamp will indicate which stamp refers to which part

of the record. When cutting the record over the weekend or holidays,

be sure to stamp the day3 s record on which no calibration was made

and fill in the check marks indicating the type of record and whether it

was connected to the HF or L.F rack. Also, the date the recording was

made. If this information is not recorded as the record is cut, the

danger of misplacing it in time sequence and losing the type and time

information is too great.

5. 3 Chart Drive Time Setting

The chart drive STOP-HOUR-MINUTE feed lever is placed in the

HOUR position for normal operation. The chart paper can be set to the

proper time by advancing the paper or moving it back through the chart

drive. The time should be set to correspond with the time on the power

recorder charts. Since the chart drives on the power and log-linear

recorders are independent spring drive clocks, the chart drive speed

may vary between the two. Therefore, it is necessary to check the

indicated time on both sets of recorders daily and reset the chart to

the correct time if necessary. If one chart drive and/or the other

gains or loses each day, the FAST-SLOW adjustment setting should be

corrected as indicated in the Esterline -Angus recorder handbook.
- 12 -

5.4 Tube Checks

As with the AR.N-2 power recorder, all of the tubes in the

C rack should be checked at least once every three months. If the tube

has been checked and the Gm noted or if the tube is a replacement

during the three-month period with its Gm recorded at the time of

replacement, it is not necessary to recheck during the regular tube

check. Any tube whose Gm value has dropped to 85% of the design

value or less must be replaced in order to achieve proper operation of

the equipment.

5. 5 Detector Meter Scales

Some confusion has been encountered in reading the value

obtained from the combination of the detector meter reading and the

scale factor indicated by the detector meter switch. The divisions on

the detector meter are indicated as db above reference, while the

scale factors indicated by the detector meter switch are in db below

reference. For this reason, it is necessary to subtract the scale

factor from the meter reading to obtain the correct reading in db's

from reference. The following examples illustrate this. If the meter

reading is +8 and the scale factor is 0, then the reading is +8 -0=+8db

or 8 db above reference. If the meter reading is +8 and the scale

factor is 40, then the reading is +8 -40 = -32 or 32 db below reference.

If the meter reading is -4 and the scale factor is 0, then the reading is

-4 -0 =; -4 or 4 db below reference. If the meter reading is -4 and the

scale factor is 20, the reading is -4 -20 = -24 or 24 db below

reference. Unfortunately, because of a combination of meter scale

limitations, it is impossible to read any value between 6 and 10 db

below reference, 26 and 30 db below reference, and 46 and 50 db

below reference.

5. 6 Log-Gate Timer Setting

The red hand on the timer should always be set for a fourminute delay. The timer settings are indicated for 60 cycle operation.

Therefore, if the line voltage supply is 60 cycle, set the red hand at

the four-minute mark. If the line voltage supply is 50 cycle, the red

hand should be set at three minutes forty seconds. This four -minute

delay in some cases may prevent a reading from being taken that could

have been obtained with a 2-l/2 or three-minute setting of the log-gate

timer However, if the power recorder is recording atmospheric

noise, the following time sequence should take place. The attenuator

will step up for as long as three minutes after a frequency change

(usually a shorter period of time is required for the attenuator to reach

the proper level if the noise is atmospheric in origin). At the end of

the three minutes, the attenuator programer will step up an additional
- 13 -

6 or 8 db (depending on whether it is the B or A rack attenuator). If the attenuator was at the correct level before the attenuator programer

stepped up the attenuator, it will have to step down a maximum of 8 db,

or possibly during sunrise periods 10 db. The time required for this

including the possible four minutes for the last step should not be more

than seven minutes. This then under extreme conditions leaves five

minutes from the last step to the end of the recording period, which is

ample time to get a valid log and linear reading. During periods of

sunrise and sunset when the average power is changing at the greatest

rate, a change of more than 10 to 12 db per hour would not be expected

on any frequency. On the basis of a linear change with time,

-T-jr or -r-jT of a db change would be the maximum change expected in

atmospheric noise power in a four -minute period. This is not enough

to ordinarily step the attenuator again in the four minutes if it is within

1 db at the beginning of the four-minute period. On the other hand, if

the noise is man-made in origin or signal, it can and very probably

will change more than the 1 db in a four -minute period, thus causing

the attenuator to step and preventing an erroneous reading from being

taken. While it is true, especially during periods of local thunderstorm activity, that some valid readings will be lost, it is felt that this

will be a small percentage of the nonvalid readings that will be

eliminated. Thus, the method of operation is felt to be worthwhile.

6. Records Processing of Log and Voltage

6. 1 General

General instructions relating to mailing, tabulating, and

frequency identification of the noise power records (ARN-2 manual,

pages 100-101) should be followed in processing log and voltage

records. Tabulation sheets should carry the designation "Log" or

"Voltage" under "TYPE OF MEASUREMENT. "

6. 2 Editing before Scaling

Before scaling log or voltage charts, check them against the

power record, and mark sections of the recording made during periods

when the power equipment is not operating normally. These sections

should not be scaled.

6. 3 Scaling

Operating with the four-minute timer setting, the record is

likely to show a single spike, in which case read (to the nearest

half db) the point of greatest deviation from chart zero. This is
- 14 -

actually a negative value (db below the power level), but the sign of the

deviation should not be recorded on the tabulation sheet. If there is

more than one spike, use the average of the point readings. When a point reading is not obtained, but rather a trace of varying amplitude,

record the average value of the varying portion. The greatest

deviation (20 or 30 db) side of both the log and voltage charts may be

distorted by noise generated in the first I. F. amplifier. It is,

therefore, necessary to check the values placed on the chart at the

daily calibration, both at the beginning and end of the period, before

scaling any values. Observe the point at which the calibration values

depart from the scale values by more than one -half db. Any values

read at deviations greater than this must be scaled using the calibration scale instead of the chart lines. Ordinarily there will be only a few readings falling in this category. If successive calibrations show

differences of more than 1 db for corresponding points on the chart

scale, the data between these calibrations should be discarded. When

using the calibration scale, use the dayJ s calibration for the record

from the preceding midnight to the following midnight. For days

when no calibration is made, use the previous calibration approximately half way through the period of no calibration and the following

calibration for the balance of the period. When two calibrations are

made for one day, use the first up to the time it was made and the

second from the time it was made.

6.4 Editing after Scaling

After tabulating the hourly values, check the log and voltage

tabulation sheets against each other, eliminating data from either log

or voltage tabulation if there is not a reading of the other parameter

for the same hour and day. For example, if there is a reading of the

log at a certain hour but none for the voltage, the log value should be

discarded; or if there is a voltage reading but none for the log,

discard the voltage reading. The recommended procedure is to place

a single red pencil mark through the discarded value. In all cases,

the log deviation should be equal to or greater than the voltage

deviation for the corresponding interval; if it is not, both values (log

and voltage) should be discarded, since an operational fault is

indicated.

6. 5 Analysis of the Records

After making the checks outlined above, determine a median

value of the deviations for the month at each hour (-see instructions for

determining the median value, ARN-2 Handbook, page 107). These

values are then recorded in the "Vdm" and "Ldm" columns on

Form RN-13. The Vdm and Ldm value recorded should be rounded
- 15 -

off to the nearest half db. For example, if the median is found to be

12. 2 db, record it as 12. db or if the median is 8. 4 db, record it as

8. 5 db. If the median is 10. 25, record this as 10. db, and if the

median is 10.75, record this as 11.0 db.

6. 6 Disposition of Data

The E-A records and the original copy of the tabulation sheets

should be sent to Boulder each month with the power recorder data.

7. References

1. W. H. Ahlbeck, W. Q. Crichlow, R. T. Disney, F. F. Fulton, Jr.

,

and C. A. Samson, "Instruction book for ARN-2 radio noise

recorder, serial numbers 1 to 10," January 3, 1958,

available from the authors.

2. W. Q. Crichlow, C. J. Roubique, A. D. Spaulding, and

W. M. Beery, "Determination of the amplitude -probability

distribution of atmospheric radio noise from statistical moments,"

J. Research NBS, 64-D (Radio Propagation), 49 (I960).

3. A. D. Watt, R. M. Coon, E. L. Maxwell, and R. W. Plush,

"Performance of some radio systems in the presence of thermal

and atmospheric noise," Proc. IRE, 46, (12) , 1914(1958).
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NATIONAL BUREAU OF STANDARDS CABLE DIAGRAM

ATMOSPHERIC RADIO NOISE RECORDER

"oobl flRN - 2

-

DWG. NO. 83452-

C
LOG CHART VOLTAGE CHART

Figure 13 Figure 14
TYPICAL VALUES ON DAILY LOG SHEET

Figure 15

U.S. DEPARTMENT OF COMMERCE

Frederick II. Mueller, Secretary NATIONAL BUREAU OF STANDARDS

A. V. Aslin, Director THE NATIONAL BUREAU OF STANDARDS

The scope of activities of the National Bureau of Standards at its major laboratories in Washington, D.C., and

Boulder, Colorado, is suggested in the following listing of the divisions and sections engaged in technical work.

In general, each section carries out specialized research, development, and engineering in the field indicated by

its title. A brief description of the activities, and of the resultant publications, appears on the inside of the front

cover. WASHINGTON, D.C.

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Optics and .Metrology. Photometry and Colorimetry. Photographic Technology. Length. Engineering

Metrology.

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Radicals Research. Atomic and Radiation Physics. Spectroscopy. Radiometry. Mass Spectrometry. Solid State Physics. Electron Physics. Atomic Physics. Neutron Physics. Radiation Theory. Radioactivity. X-rays. High

Energy Radiation. Nucleonic Instrumentation. Radiological Equipment.

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Physics.

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Digital Systems. Analog Systems. Application Engineering.

• Office of Basic Instrumentation. • Office of Weights and Measures. BOULDER, COLORADO

Cryogenic Engineering. Cryogenic Equipment. Cryogenic Processes. Properties of Materials. Gas Liquefaction. Radio Propagation Physics. Upper Atmosphere Research. Ionospheric Research. Regular Propagation

Services. Sun-Earth Relationships. VHF Research. Radio Warning Services. Airglow and Aurora. Radio

Astronomy and Arctic Propagation.

Radio Propagation Engineering. Data Reduction Instrumentation. Modulation Research. Radio Noise. Tropospheric Measurements. Tropospheric Analysis. Propagation Obstacles Engineering. Radio-Meteorology. Lower Atmosphere Physics.

Radio Standards. High Frequency Electrical Standards. Radio Broadcast Service. High Frequency Impedance Standards. Electronic Calibration Center. Microwave Physics. Microwave Circuit Standards. Radio Communication and Systems. Low Frequency and Very Low Frequency Research. High Fre- quency and Very High Frequency Research. Ultra High Frequency and Super II igh Frequency Research. Modulation Research. Antenna Research. Navigation Systems. Systems Analysis. Field Operations.

U5C0MM-NBS-81.