NTIA Report 02-390

Man-Made Noise Power Measurements

at VHF and UHF Frequencies

Robert J. Achatz

Roger A. Dalke

U.S. DEPARTMENT OF COMMERCE

Donald L. Evans, Secretary

Nancy J. Victory, Assistant Secretary

for Communications and Information

December 2001
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iii

Product Disclaimer

Certain commercial equipment, instruments, or materials are identified in this report to specify

the technical aspects of the reported results. In no case does such identification imply

recommendation or endorsement by the National Telecommunications and Information

Administration, nor does it imply that the material or equipment identified is necessarily the best

available for the purpose.
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v

CONTENTS

Page

FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi

TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii

ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1. INTRODUCTION ...........................................................1

1.1 Background and Terminology ...........................................2

1.1.1 Noise Voltage Representations ...................................2

1.1.2 Instantaneous Noise Power ......................................2

1.1.3 Statistics of Instantaneous Noise Power ............................3

1.1.4 Average Noise Power ..........................................4

1.1.5 Antenna Average Noise Power ...................................5

1.1.6 Noise Power Statistics ..........................................5

1.2 Predicted Noise Power .................................................6

2. MEASUREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.1 Frequencies .........................................................7

2.2 Measurement Sites and Duration .........................................7

2.3 Equipment ..........................................................8

2.4 Data Acquisition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3. DATA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

3.1 APD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

3.2 24-hour Summaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

4. RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

5. CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

6. REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

APPENDIX: NOISE MEASUREMENT SYSTEM SPECIFICATIONS . . . . . . . . . . . . . . . . . . 31
vi

FIGURES

Page

Figure 1. Natural and man-made antenna noise figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Figure 2. Block diagram of noise measurement system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Figure 3. Block diagram of spectrum analyzer shown in Figure 2 . . . . . . . . . . . . . . . . . . . . . . 8

Figure 4. APD of system noise power at 137.5 MHz with residential equipment 

configuration. Gain and noise figure are 44.7 dB and 1.8 dB respectively . . . . . . . 10

Figure 5. 137.5 MHz noise from measurements at Lakewood, Colorado residence on 

Tuesday, April 27, 1999 at 10:28:26 AM. Noise figure is 10.0 dB . . . . . . . . . . . . . 12

Figure 6. 137.5 MHz noise from measurements at Boulder, Colorado residence on 

Friday, May 21, 1999 at 03:38:55 PM. Noise figure is 8.1 dB . . . . . . . . . . . . . . . . . 12

Figure 7. 137.5 MHz noise from measurements at downtown Boulder, Colorado on 

Friday, July 9, 1999 at 11:06:35 AM. Noise figure is 25.8 dB . . . . . . . . . . . . . . . . . 13

Figure 8. 137.5 MHz noise from measurements at downtown Denver, Colorado on 

Monday, August 30, 1999 at 10:52:04 AM. Noise figure is 16.7 dB . . . . . . . . . . . . 13

Figure 9. 402.5 MHz noise from measurements at Lakewood, Colorado residence on

Wednesday, May 26, 1999 at 12:57:44 PM. Noise figure is 1.7 dB . . . . . . . . . . . . . 14

Figure 10. 402.5 MHz noise from measurements at Boulder, Colorado residence on 

Thursday, May 13, 1999 at 12:58:50 PM. Noise figure is 2.3 dB . . . . . . . . . . . . . . 14

Figure 11. 402.5 MHz noise from measurements at downtown Boulder, Colorado on 

Thursday, July 1, 1999 at 12:51:52 PM. Noise figure is 3.1 dB . . . . . . . . . . . . . . . . 15

Figure 12. 402.5 MHz noise from measurements at downtown Denver, Colorado on

Wednesday, August 25, 1999 at 09:52:57 AM. Noise figure is 8.6 dB . . . . . . . . . . 15

Figure 13. 761.0 MHz noise from measurements at Lakewood, Colorado residence on 

Thursday, April 29, 1999 at 11:55:15 AM. Noise figure is 2.8 dB . . . . . . . . . . . . . 16

Figure 14. 761.0 MHz noise from measurements at Boulder, Colorado residence on 

Wednesday, May 19, 1999 at 12:56:22 PM. Noise figure is 2.1 dB . . . . . . . . . . . . . 16
vii

FIGURES (cont.)

Page

Figure 15. 761.0 MHz noise from measurements at downtown Boulder, Colorado on 

Monday, July 5, 1999 at 02:55:56 PM. Noise figure is 2.5 dB . . . . . . . . . . . . . . . . 17

Figure 16. 761.0 MHz noise from measurements at downtown Denver, Colorado on 

Friday, August 27, 1999 at 07:31:10 PM. Noise figure is 2.5 dB . . . . . . . . . . . . . . 17

Figure 17. 137.5 MHz median, mean, and peak power at Lakewood, Colorado residence on

Tuesday, April 27, 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 18. 137.5 MHz median, mean, and peak power at Boulder, Colorado residence on 

Friday, May 21, 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 19. 137.5 MHz median, mean, and peak power at downtown Boulder, Colorado on

Friday, July 9, 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Figure 20. 137.5 MHz median, mean, and peak power at downtown Denver, Colorado on

Monday, August 30, 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Figure 21. 402.5 MHz median, mean, and peak power at Lakewood, Colorado residence on

Wednesday, May 26, 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Figure 22. 402.5 MHz median, mean, and peak power at Boulder, Colorado residence on

Thursday, May 13, 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Figure 23. 402.5 MHz median, mean, and peak power at downtown Boulder, Colorado on

Thursday, July 1, 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Figure 24. 402.5 MHz median, mean, and peak power at downtown Denver, Colorado on

Wednesday, August 25, 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Figure 25. 761.0 MHz median, mean, and peak power at Lakewood, Colorado residence on

Thursday, April 29, 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Figure 26. 761.0 MHz median, mean, and peak power at Boulder, Colorado residence on

Wednesday, May 19, 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Figure 27. 761.0 MHz median, mean, and peak power at downtown Boulder, Colorado on

Monday, July 5, 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
viii

FIGURES (cont.)

Page

Figure 28. 761.0 MHz median, mean, and peak power at downtown Denver, Colorado on

Friday, August 27, 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Figure 29. Cumulative distributions of 137.5 MHz residential median, mean, and 

peak power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Figure 30. Cumulative distributions of 137.5 MHz business median, mean, and 

peak power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Figure 31. Cumulative distributions of 402.5 MHz residential median, mean, and 

peak power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 32. Cumulative distributions of 402.5 MHz business median, mean, and 

peak power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 33. Cumulative distributions of 761.0 MHz residential median, mean, and 

peak power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Figure 34. Cumulative distributions of 761.0 MHz business median, mean, and 

peak power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

TABLES

Page

Table 1. Natural and Man-made Fam (dB above kT0b) at Measurement Frequencies . . . . . . . . 6

Table 2. System Noise Figures (dB above kT0b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Table 3. Measured Fm for All Frequencies and Environments . . . . . . . . . . . . . . . . . . . . . . . . 25
*

 The authors are with the Institute for Telecommunication Sciences, National Telecommunications and

Information Administration, U.S. Department of Commerce, Boulder, CO 80305.

MAN-MADE NOISE POWER MEASUREMENTS AT VHF AND UHF FREQUENCIES

Robert J. Achatz and Roger A. Dalke*

Man-made noise generated by automotive ignition, power distribution and transmission,

industrial equipment, consumer products, and lighting systems degrades the performance of

radio systems. Man-made noise models, derived from measurements made in the 1970s, may

be inaccurate due to changes in these technologies. For example, recent man-made noise

measurements performed by ITS in the 136 to 138 MHz meteorological satellite band

indicated that man-made noise power in residential areas is lower than predictions by these

models. However, these same measurements indicated that man-made noise in business areas

has not changed. UHF man-made noise has not been comprehensively measured and modeled.

This report describes UHF man-made noise measurements conducted in the Denver, CO

metropolitan area in 1999. Measurement data is analyzed and results are compared to other

measurements and models. These results showed that 402.5 MHz UHF noise levels in

business areas were high enough to adversely affect communication system performance some

of the time.

Key words: radio channel, man-made noise, impulsive noise, non-Gaussian noise, simulation of

communication systems, noise measurement, noise modeling

1. INTRODUCTION

Man-made noise power was measured comprehensively 25-35 years ago [1]. These

measurements, conducted from 0.25 to 250 MHz, were used to develop the CCIR [2] and current

ITU-R [3] man-made noise model commonly used in radio link design to this day. Since that

time no comprehensive man-made noise power measurements have been made, in spite of the

fact that technological changes may have made this model inaccurate. In 1996 the Institute for

Telecommunication Sciences (ITS) conducted man-made noise power measurements at 137

MHz for the National Oceanic and Atmospheric Administration (NOAA) [4] which had been

tasked with converting space-to-earth VHF analog-modulated radio links to digital modulation.

The measurements showed that VHF man-made noise power has decreased in residential areas

and has remained constant in business and rural areas.

Predicting whether UHF frequencies would follow the same trend as VHF frequencies is

difficult. For example, noise due to automotive ignition systems may have also decreased in UHF

frequencies as it did at VHF frequencies; however, modern electronic devices such as personal

computers and pulse-width modulated motor drives may have increased noise. All these factors

point to the need for a comprehensive man-made noise measurement and analysis campaign.
2

As a beginning, ITS has performed a limited set of noise power measurements at VHF and UHF

frequencies in business and residential settings at 137.5 MHz, 402.5 MHz, and 761.0 MHz.

These measurements were collected between April and August of the year 1999 in the Denver,

CO metropolitan area. Instantaneous and long term noise power statistics were included in the

measurement data analysis.

1.1. Background and Terminology

1.1.1 Noise Voltage Representations

A noise voltage is a random function of time whose behavior can only be described statistically.

The time-varying noise voltage, v(t), is represented as a passband signal centered about a carrier

frequency, fc,

(1.1)

where Re{} denotes the real part and (t) is the noise voltage complex baseband signal centered

about 0 Hz that can be represented in Cartesian or polar form as follows:

(1.2)

where x(t) and y(t) are the baseband signal real and imaginary components, respectively. Both v(t)

and (t) are random processes defined by one or more random variables. For example, if v(t) is

white Gaussian noise, the real and imaginary components are independent and identically

distributed zero-mean Gaussian random variables whose power spectral density (PSD) is flat.

The corresponding amplitude is Rayleigh distributed while the phase is uniformly distributed.

1.1.2 Instantaneous Noise Power

We define the instantaneous noise power as

(1.3)

In this report the instantaneous noise power is normalized by the average noise power due to

black body radiation and thermal noise that is present in all radio systems. This average noise

power is kT0b where k = 1.38x10-23 W/Hz/K is Boltzman’s constant, T0 = 288K is the absolute

temperature, and b is the receiver noise equivalent bandwidth.
3

1.1.3 Statistics of Instantaneous Noise Power

The cumulative distribution function (CDF) of instantaneous noise power describes the

probability that the noise power will not exceed a value 

(1.4)

where WRV is the noise power random variable, w is the noise power independent variable, and

p(w) is the probability density function (PDF) of the noise power random variable. Radio

engineers are concerned with the probability that the noise power will exceed a value. This

probability is expressed as

(1.5)

and is customarily referred to as the amplitude probability distribution function (APD).

For white Gaussian noise, the amplitude PDF, expressed in w, is

(1.6)

where w0 is Fx

2

 + Fy

2

 which is equivalent to the average power of w. The amplitude CDF,

expressed in w, is

(1.7)

and the APD, expressed in w, is 

(1.8)

Receiver performance can be predicted from the APD [5,6]. The APD, in turn, is dependent on

the bandwidth of the measurement, bandwidth of the noise, and time intervals between noise

pulses. The APD of zero-mean, white Gaussian noise is completely described by its mean power;

therefore the performance of a receiver in white noise can be predicted from mean noise power

alone.
4

(1.9)

In this report APD’s are plotted on a Rayleigh probability graph whose axes represent the

amplitude in dB above kT0b and the percent-of-time the amplitude is exceeded. On a Rayleigh

probability graph, noise with a Rayleigh amplitude distribution forms a straight line with slope 

-1/2 . Impulsive noise is represented by amplitudes that exceed this line at low probabilities.

Continuous wave interference is represented by an approximately straight line with a slope that

approaches zero as the signal-to-noise ratio increases.

Mean, median, and peak statistical functions are commonly used to characterize noise power.

The mean power statistic is described in the next section. Median is the power which is exceeded

50% of the time and peak is somewhat arbitrarily defined to be the power that is exceeded 0.01%

of the time. For white Gaussian noise with Rayleigh distributed amplitudes, the mean lies on the

37.0 percentile and the median and peak are 1.6 dB below and 9.6 dB above this mean value,

respectively.

1.1.4 Average Noise Power

Zero-mean Gaussian noise is completely described by its variance, which is equivalent to the

average noise power. The average noise power does not completely describe non-Gaussian noise

but is vitally important. The average noise power is defined as

where E{} denotes the expected value of its argument. The average noise power relative to kT0b

is called the noise factor and is given by

(1.10)

and the noise figure in dB is

(1.11)

Noise sources are often specified in terms of temperature, t. Temperature in K and noise factor is

related by 

(1.12)
5

1.1.5 Antenna Average Noise Power

The noise collected by the antenna originates, presumably, from widely scattered directions at or

near the horizon and is therefore altered by the receiving station antenna directional gain. If

S(2,N) is the power density coming from elevation 2 and azimuth N; and g(2,N) is the antenna

directional gain relative to isotropic, the total noise power received by an antenna is 

(1.13)

where 8 is the wavelength. The corresponding antenna noise factor is 

(1.14)

A noise power measurement system consists of an antenna, antenna matching circuit,

transmission line, and receiver. If the antenna matching circuit and transmission line are assumed

to be lossless and operating at a temperature T0, the measured noise factor is related to the

antenna noise factor and receiver noise factor by

(1.15)

where f is the measured noise factor and fr is the receiver noise factor.

1.1.6 Noise Power Statistics

Man-made noise power statistics are non-stationary in that they have been found to vary over

time and location. The statistical behavior of noise power can be shown by plotting the

distribution on a normal probability graph where random variables that are Gaussian distributed

form a straight line with a slope equal to its standard deviation and a median equal to its mean.

The normal probability graph can be used to display within-the-hour, hour-to-hour, and locationto-location noise power statistics.
6

1.2 Predicted Noise Power

Noise power present for 50% of the time and 50% of the locations is predicted as a function of

frequency by

(1.16)

where c and d are constants and f is frequency in MHz. Fam is derived from an ensemble of fa

defined in Equation 1.15. Below 200 MHz, the longstanding ITU-R model provides values of

76.8, 72.5, and 67.2 dB for c for business, residential, and rural environments and 27.7 dB/MHz

for d. Above 200 MHz, Hagn [7] provides values of 49.2, 45.2, and 39.3 dB for c for business,

residential, and rural environments and 15.8 dB/MHz for d. These values were based on the

extrapolation of a number of lower UHF frequency spot measurements reported in the literature.

Lauber [8] analyzed man-made noise power measurements obtained in 5 business, 10 residential

and 2 rural environments at 600, 700, 800, and 900 MHz with a 100 kHz bandwidth. These

measurements agreed well with Hagn’s predictions.

Natural noise is produced by extraterrestrial and atmosphere sources. The total power is

dependent upon the directionality of the source and receiving antenna. The omnidirectional

antenna used in these measurements effectively attenuates the noise power of directional sources.

The sun, galactic center, cosmos, and atmospheric water vapor all have insignificant noise

powers when measured with an omnidirectional antenna. Galactic noise may not be insignificant.

Figure 1 summarizes noise power trends over a wide frequency range. Table 1 provides an

estimate of natural and man-made noise power at the measurement frequencies.

Table 1. Natural and Man-made Fam (dB above kT0b) at Measurement Frequencies

Environment/type

Frequency (MHz)

137.5 402.5 761.0

Business 17.6 8.1 3.7

Residential 13.2 4.1 -0.3

Rural 8.0 -1.9 -6.3

Galactic 2.8 -7.9 -14.3

For comparison, values of previous ITS measurements at 137.5 MHz are 18.0, 6.0, and 6.3 dB

for business, residential, and rural environments. These measurements showed that recent

business and rural noise powers are similar to older measurements but residential man-made
7

-20

-10

0

10

20

30

100 200 300 400 500 600 700 800 1000

Business

Residential

Rural

Galactic

Frequency (MHz)

F

am(dB)

Figure 1. Natural and man-made antenna noise figures.

noise may have decreased. Measurements and analysis for this report will attempt to estimate

corresponding values for business and residential man-made noise power at 402.5 and 761.0

MHz.

2. MEASUREMENTS

2.1 Frequencies

Three frequencies, 137.5 MHz, 402.5 MHz, and 761.0 MHz, were measured. The 137.5 MHz

frequency is a VHF meteorological satellite space-to-earth allocation. This is the same frequency

measured in the NOAA work described earlier. The 402.5 MHz frequency is in the UHF

meteorological aids band extending from 400 to 406 MHz. No intentional signals at this

frequency were detected at any of the measurement locations. The 761.0 MHz frequency is the

center of a 6 MHz UHF television broadcast band channel. No television signals were found in

this television channel or in adjacent television channels during the measurements. 

2.2 Measurement Sites and Duration

Measurements were conducted in the Denver metropolitan area between April and August of the

year 1999. They were acquired continuously over time periods lasting several days. This is a

prudent approach for initial measurements since it allows trends in noise power statistics to be

correlated with cultural patterns such as working hours and weekdays.
8

Figure 3. Block diagram of spectrum analyzer shown in Figure 2.

Figure 2. Block diagram of noise measurement system.

Two residential and two business locations in two cities were chosen to assure spatial

independence. The first residential measurement was performed at a residence in Lakewood, CO

approximately 10 miles west of downtown Denver, CO. The second residential measurement was

performed at a residence in Boulder, CO approximately 3 miles south of downtown Boulder, CO.

The business measurements were performed in downtown Boulder, CO and downtown Denver,

CO.

2.3 Equipment 

Man-made noise power measurements were acquired with the system depicted in Figures 2 and

3. The equipment specifications are detailed in the Appendix. The quarter-wave monopole

antenna was mounted on a ground plane to assure an omnidirectional pattern whose gain is

maximum at or near the horizon. The signal captured by the antenna was preselection-filtered to

attenuate out-of-band power and preamplified to increase system sensitivity. The spectrum

analyzer, tuned to the measurement frequency, down-converted the signal to the final

intermediate-frequency where it was resolution bandwidth-filtered and log amplified. Noise

power samples were obtained by digitizing the output of the envelope detector.
9

The resolution bandwidth filter was Gaussian shaped and had a 3-dB bandwidth of 30 kHz and a

corresponding noise equivalent bandwidth of 36 kHz. The thermal noise floor, kT0b, was

approximately -128 dBm and the 1-dB compression point at the preselection filter input was

approximately -55 dBm.

The slope of the log amplifier calibration curve in units of dB/volt was constant from -100 to -10

dBm spectrum analyzer input power. These input powers correspond to 0.1 to 1.0 volt direct

current at the output of the log amplifier. Gain from the preselection-filter input to the spectrum

analyzer input was adjusted so that noise below kT0b was measurable and the 1-dB compression

point was never exceeded. A gain of 44 dB provided a dynamic range extending from -144 dBm

to -54 dBm. This range corresponds to 16 dB below kT0b to 74 dB above kT0b.

For business measurements the spectrum analyzer, preamplifier, and preselection filter were

installed in a van. The antenna was attached to a rectangular 1.5 m by 3.0 m (5 ft by 10 ft) ground

plane welded to the van roof. In this configuration the cable from the preamplifier output to the

spectrum analyzer input was 3 m (10 ft) long. For residential measurements the spectrum

analyzer was sheltered by a garage while the preselection filter and preamplifier were housed

outside in a waterproof container. The antenna was attached to a 1.2-m (4-ft) diameter, circular

ground plane. In this configuration the cable from the preamplifier output to the spectrum

analyzer input was 7.6 m (25 ft) long.

Gain was accurately measured by applying a strong sinusoidal signal to the preselection-filter

input and then to the spectrum analyzer input. System noise was measured by replacing the

antenna with a 50-ohm load. A system noise APD is shown in Figure 4. The straight APD

demonstrates that the system noise is Gaussian. System noise statistics for all other frequencies

and configurations also were Gaussian distributed. Corresponding measured noise figures are

reported in the following table.

Table 2. System Noise Figures (dB above kT0b)

Configuration

Frequency (MHz)

137.5 402.5 761.0

Business 1.8 0.8 3.2

Residential 1.8 1.9 2.9
10

-20

0

20

40

60

.01 .1 1 5 10 25 37 50 70 80 95 99

Percent exceeding ordinate

dB above kT0 b

Figure 4. APD of system noise power at 137.5 MHz with residential

equipment configuration. Gain and noise figure are 44.7 dB and

1.8 dB respectively.

2.4 Data Acquisition

The voltage at the output of the log amplifier was digitized with a 12-bit analog-to-digital

converter (ADC). The ADC amplified the log amplifier output voltage by a factor of ten and then

sampled it. The samples were converted to dBm and the gain in dB from the preselector input to

the spectrum analyzer input was subtracted.

The basic noise power measurement contains 60,000 samples acquired at a rate of 1,000

samples/sec in 1-second bursts. The entire 60,000 samples were acquired in less than 3 minutes.

The measurement system was not moved during this time and the noise statistics were assumed

to be stationary over this time interval. Statistics of the samples were archived in a measurement

histogram. The histogram bins range from -154 to -54 dBm, or 26 dB below kT0b to 74 dB above

kT0b in 0.1-dB steps.
11

3. DATA

3.1 APD

Representative man-made noise APDs, shown in Figures 5-16, characterize short term noise

behavior. Of particular interest are the median, mean, and peak power, the percentage where the

APD deviates from the straight Gaussian APD, and the shape of the low probability nonGaussian component.

Figures 5 and 6 are representative of 137.5 MHz residential noise. The APD departs from

Gaussian at 1% or less. The low probabilities are rectangular shaped, indicating little variation in

amplitudes of the non-Gaussian component. Figures 7 and 8 depict 137.5 MHz business noise.

Median, mean, and peak powers are high compared to system noise. The Denver, CO APD nonGaussian component departs from Gaussian at 5%. This is high in comparison to the other

representative APDs.

Figures 9 and 10 are representative of 402.5 MHz residential noise. In Figure 9 the non-Gaussian

component departs from Gaussian at approximately the same percentile as 137.5 MHz

residential. However, the non-Gaussian component is triangular rather than rectangular. The

median is comparable to the system noise median and the peak has little effect on the mean.

Figure 10 indicates Gaussian noise statistics. Figures 11 and 12 depict 402.5 MHz business

noise. The Denver, CO APD non-Gaussian component departs from Gaussian at 5%. This high

probability has a definite effect on mean power.

Figures 13 and 14 are representative of 761.0 MHz residential noise. Both have Gaussian noise

statistics with means comparable to those of system noise. Figures 15 and 16 depict 761.0 MHz

business noise. The non-Gaussian components depart from Gaussian at 1% or less and have little

effect on mean power.
12

-20

0

20

40

60

.01 .1 1 5 10 25 37 50 70 80 95 99

Percent exceeding ordinate

dB above kT0 b

Figure 6. 137.5 MHz noise from measurements at Boulder,

Colorado residence on Friday, May 21, 1999 at 03:38:55

PM. Noise figure is 8.1 dB.

-20

0

20

40

60

.01 .1 1 5 10 25 37 50 70 80 95 99

Percent exceeding ordinate

dB above kT0 b

Figure 5. 137.5 MHz noise from measurements at Lakewood,

Colorado residence on Tuesday, April 27, 1999 at

10:28:26 AM. Noise figure is 10.0 dB.
13

0

20

40

60

.01 .1 1 5 10 25 37 50 70 80 95 99

Percent 

dB above kT0 b

Figure 7. 137.5 MHz noise from measurements at downtown

Boulder, Colorado on Friday, July 9, 1999 at 11:06:35

AM. Noise figure is 25.8 dB.

-20

0

20

40

60

.01 .1 1 5 10 25 37 50 70 80 95 99

Percent exceeding ordinate

dB above kT0 b

Figure 8. 137.5 MHz noise from measurements at downtown

Denver, Colorado on Monday, August 30, 1999 at

10:52:04 AM. Noise figure is 16.7 dB.
14

-20

0

20

40

60

.01 .1 1 5 10 25 37 50 70 80 95 99

Percent exceeding ordinate

dB above kT0 b

Figure 10. 402.5 MHz noise from measurements at Boulder,

Colorado residence on Thursday, May 13, 1999 at

12:58:50 PM. Noise figure is 2.3 dB.

-20

0

20

40

60

.01 .1 1 5 10 25 37 50 70 80 95 99

Percent exceeding ordinate

dB above kT0 b

Figure 9. 402.5 MHz noise from measurements at Lakewood,

Colorado residence on Wednesday, May 26, 1999 at

12:57:44 PM. Noise figure is 1.7 dB.
15

-20

0

20

40

60

.01 .1 1 5 10 25 37 50 70 80 95 99

Percent exceeding ordinate

dB above kT0 b

Figure 12. 402.5 MHz noise from measurements at downtown

Denver, Colorado on Wednesday, August 25, 1999 at

09:52:57 AM. Noise figure is 8.6 dB.

-20

0

20

40

60

.01 .1 1 5 10 25 37 50 70 80 95 99

Percent exceeding ordinate

dB above kT0 b

Figure 11. 402.5 MHz noise from measurements at downtown

Boulder, Colorado on Thursday, July 1, 1999 at

12:51:52 PM. Noise figure is 3.1 dB.
16

-20

0

20

40

60

.01 .1 1 5 10 25 37 50 70 80 95 99

Percent exceeding ordinate

dB above kT0 b

Figure 13. 761.0 MHz noise from measurements at Lakewood,

Colorado residence on Thursday, April 29, 1999 at

11:55:15 AM. Noise figure is 2.8 dB.

-20

0

20

40

60

.01 .1 1 5 10 25 37 50 70 80 95 99

Percent exceeding ordinate

dB above kT0 b

Figure 14. 761.0 MHz noise from measurements at Boulder,

Colorado residence on Wednesday, May 19, 1999 at

12:56:22 PM. Noise figure is 2.1 dB.
17

-20

0

20

40

60

.01 .1 1 5 10 25 37 50 70 80 95 99

Percent exceeding ordinate

dB above kT0 b

Figure 15. 761.0 MHz noise from measurements at downtown

Boulder, Colorado on Monday, July 5, 1999 at

02:55:56 PM. Noise figure is 2.5 dB.

-20

0

20

40

60

.01 .1 1 5 10 25 37 50 70 80 95 99

Percent exceeding ordinate

dB above kT0 b

Figure 16. 761.0 MHz noise from measurements at downtown

Denver, Colorado on Friday, August 27, 1999 at

07:31:10 PM. Noise figure is 2.5 dB.
18

3.2 24-hour Summaries

Figures 17-28 summarize long term noise behavior by plotting the peak, mean, and median noise

power as a function of time. The median, mean, and peak powers are the bottom, middle, and top

curves respectively of these graphs. Noise added by the measurement system has not been

removed from these values. These graphs show how noise power statistics are correlated with

time of day.

The 24-hour summary graphs show that median power varied much less than mean and peak

power for all frequencies and locations. The only exception to this was when a weather satellite,

which transmits an FM modulated signal at 137.5 MHz, was in view. Several examples of this,

noticeable by the large increase in median noise power, can be found between 4:00 a.m. and

10:00 a.m. at the Lakewood, CO residence shown in Figure 17. Median power was typically very

close to system noise median power. The main exception to this was the 137.5 MHz business

measurements where it is elevated more than 10 dB.

Mean power was higher than system noise mean power for 137.5 MHz business, 137.5 MHz

residential and 402.5 MHz business measurements. The increase in 402.5 MHz business mean

power is most dramatically demonstrated in the downtown Denver, CO measurement shown in

Figure 24.

Peak power variation was evident for all but 761.0 MHz residential measurements. In general,

peak power was higher for business than residential and decreased with increasing frequency. Of

the three power statistics, only peak power consistently showed higher levels during working

hours. This is particularly evident in the downtown Boulder, CO measurements.

Gaussian noise, evident from the approximately 10-dB spread between mean and peak powers,

was dominant at most frequencies and environments between midnight and 6:00 a.m. The most

significant exception to this is the 402.5 MHz business downtown, Denver, CO measurement

where Gaussian statistics were observed between 10:00 a.m. and 2:00 p.m. Gaussian noise was

present at 761.0 MHz residential measurements the whole day.
19

0

20

40

60

0 5 10 15 20 25

Hour

dB above kT0 b

Figure 17. 137.5 MHz median, mean, and peak power at Lakewood,

Colorado residence on Tuesday, April 27, 1999.

0

20

40

60

0 5 10 15 20 25

Hour

dB above kT0 b

Figure 18. 137.5 MHz median, mean, and peak power at Boulder,

Colorado residence on Friday, May 21, 1999.
20

0

20

40

60

0 5 10 15 20 25

Hour

dB above kT0 b

Figure 19. 137.5 MHz median, mean, and peak power at downtown

Boulder, Colorado on Friday, July 9, 1999.

0

20

40

60

0 5 10 15 20 25

Hour

dB above kT0 b

Figure 20. 137.5 MHz median, mean, and peak power at downtown

Denver, Colorado on Monday, August 30, 1999.
21

0

10

20

30

40

0 5 10 15 20 25

Hour

dB above kT0 b

Figure 22. 402.5 MHz median, mean, and peak power at Boulder,

Colorado residence on Thursday, May 13, 1999.

0

10

20

30

40

0 5 10 15 20 25

Hour

dB above kT0 b

Figure 21. 402.5 MHz median, mean, and peak power at Lakewood,

Colorado residence on Wednesday, May 26, 1999.
22

0

10

20

30

40

0 5 10 15 20 25

Hour

dB above kT0 b

Figure 23. 402.5 MHz median, mean, and peak power at downtown

Boulder, Colorado on Thursday, July 1, 1999.

0

10

20

30

40

0 5 10 15 20 25

Hour

dB above kT0 b

Figure 24. 402.5 MHz median, mean, and peak power at downtown

Denver, Colorado on Wednesday, August 25, 1999.
23

0

10

20

30

40

0 5 10 15 20 25

Hour

dB above kT0 b

Figure 25. 761.0 MHz median, mean, and peak power at Lakewood,

Colorado residence on Thursday, April 29, 1999.

0

10

20

30

40

0 5 10 15 20 25

Hour

dB above kT0 b

Figure 26. 761.0 MHz median, mean, and peak power at Boulder,

Colorado residence on Wednesday, May 19, 1999.
24

0

10

20

30

40

0 5 10 15 20 25

Hour

dB above kT0 b

Figure 27. 761.0 MHz median, mean, and peak power at downtown

Boulder, Colorado on Monday, July 5, 1999.

0

10

20

30

40

0 5 10 15 20 25

Hour

dB above kT0 b

Figure 28. 761.0 MHz median, mean, and peak power at downtown

Denver, Colorado on Friday, August 27, 1999.
25

4. RESULTS

The statistics of man-made noise power typically vary over time and between locations and

hence, in general are non-stationary. Analysis of the non-stationarity was determined by

calculating hourly median values from the median, mean, and peak power statistics of the

measured APDs. These hourly median values were then sorted into CDFs, as shown in Figures

29-34. The median, mean, and peak powers are the bottom, middle, and top curves respectively

of these graphs. Noise added by the measurement system has not been removed from these

values. 

The CDFs were plotted on a normal probability graph where a Gaussian distributed variable is

represented by a straight line whose mean lies on the 50th percentile and the slope is the standard

deviation. The statistics of the means are approximately Gaussian for most frequencies and

environments if the lowest 5% are not included. Similarly the medians are also approximately

Gaussian. However, the peaks are clearly non-Gaussian.

Of particular interest is the mean-power CDF median. In principle, this value represents the mean

power exceeded for 50% of the time and 50% of the locations. These values denoted as Fm are

tabulated in Table 3. For clarification, Fm is derived from the f in Equation 1.15 while Fam is

derived from fa. In other words Fm includes system noise power while Fam does not. Fam for 137.5

MHz business and residential are 17.5 dB and 3.6 dB respectively. These results agree with

earlier 137.5 MHz measurements that showed a decrease in residential noise and no change in

business noise from the ITU model.

The 402.5 MHz and 761.0 MHz Fm are all within one standard deviation of system noise. As a

result, we could not determine Fam with any reasonable accuracy. This result is significant since

this means man-made noise power is less than that predicted by the Hagn model.

Table 3. Measured Fm for All Frequencies and Environments

Environment/type

Frequency (MHz)

137.5 402.5 761.0

Fm (dB) F (dB) Fm (dB) F (dB) Fm (dB) F (dB)

Business 17.6 1.5 2.2 1.4 2.6 0.9

Residential 4.5 1.6 2.6 1.4 2.9 0.4
26

0

10

20

30

40

50

1 5 10 20 30 50 70 80 90 95 99 99.9

Percent exceeding ordinate

dB above kT0 b

Figure 29. Cumulative distributions of 137.5 MHz residential

median, mean, and peak power.

0

10

20

30

40

50

1 5 10 20 30 50 70 80 90 95 99 99.9

Percent exceeding ordinate

dB above kT0 b

Figure 30. Cumulative distributions of 137.5 MHz business median,

mean, and peak power.
27

0

10

20

30

40

1 5 10 20 30 50 70 80 90 95 99 99.9

Percent exceeding ordinate

dB above kT0 b

Figure 31. Cumulative distributions of 402.5 MHz residential

median, mean, and peak power.

0

10

20

30

40

1 5 10 20 30 50 70 80 90 95 99 99.9

Percent exceeding ordinate

dB above kT0 b

Figure 32. Cumulative distributions of 402.5 MHz business median,

mean, and peak power.
28

0

10

20

30

40

1 5 10 20 30 50 70 80 90 95 99 99.9

Percent exceeding ordinate

dB above kT0 b

Figure 33. Cumulative distributions of 761.0 MHz residential

median, mean, and peak power.

0

10

20

30

40

1 5 10 20 30 50 70 80 90 95 99 99.9

Percent exceeding ordinate

dB above kT0 b

Figure 34. Cumulative distributions of 761.0 MHz business median,

mean, and peak power.
29

5. CONCLUSIONS

Man-made, non-Gaussian noise was observable in all 137.5 MHz and 402.5 MHz business and

residential measurements. It was also found at 761.0 MHz in business measurements but absent,

for all practical purposes, at 761.0 MHz in residential measurements. VHF measurements were

found to be consistent with previous measurements [4]. As in the previous study, 137.5 MHz

residential Fam seems to have decreased from levels measured 25-30 years ago, while 137.5 MHz

business Fam has remained constant.

The UHF measurements showed that median mean power at 402.5 MHz and 761.0 MHz is

comparable to system noise, indicating that Fam may be less than those predicted by Hagn’s

model [7]. It should be noted, however, that the 402.5 MHz business noise cumulative

distribution shown in Figure 32 is peaked. Noise levels at low percentiles are high enough to

adversely affect some communication systems. Figure 24 characterizes the long term statistics of

this noise. Noise levels are correlated to working hours in that they rise in the morning and fall in

the afternoon. However, it is noteworthy that high noise levels are not present during the middle

of the day.

Further measurements are needed to determine the extent of these high noise levels. Sources for

this noise, such as modern electronic devices, are more likely to be used within buildings and

vehicles. Hence, it is important to make future measurements inside of buildings and vehicles.
30

6. REFERENCES

[1] A.D. Spaulding and R.T. Disney, “Man-made radio noise, part 1: Estimates for business,

residential, and rural areas,” Office of Telecommunications Report 74-38, Jun. 1974. 

[2] CCIR, “Man-made radio noise,” Report 258-5, International Radio Consultative Committee,

International Telecommunication Union, Geneva, Switzerland, 1990.

[3] ITU-R Recommendations, “Radio Noise,” ITU-R P.372-6, Vol. 1997, P Series-Part 1, pp.

49-124.

[4] R.J. Achatz, R.A. Dalke, G.A. Hufford, and Y. Lo, “Man-made noise in the 136-138 MHz

VHF meteorological satellite band,” NTIA Report 98-355, Sep. 1998. 

[5] A.D. Spaulding, “Digital system performance software utilizing noise measurement data,”

NTIA Report 82-95, Feb. 1982.

[6] R.J. Achatz and R.D. Dalke, “VHF space-to-earth radio link performance in various manmade noise environments,” in Proc. of the 1998 Radio and Wireless Conf., Colorado

Springs, Co., Aug. 9-12, 1998, pp. 257-260. 

[7] G.H. Hagn, “Man-made radio noise and interference,” in Proc. of the 1987 AGARD Conf.,

No. 420, Lisbon, Portugal, Oct. 26-30 1987, pp. 5.1-5.15.

[8] W.R. Lauber and J.M. Bertrand, “Man-made noise level measurements of the UHF radio

environment,” in Proc. of the 1984 IEEE National Symposium on EMC, San Antonio, TX,

Apr. 1984.
31

APPENDIX: NOISE MEASUREMENT SYSTEM SPECIFICATIONS

A.1 Component Specifications

Antenna: Quarter-wave monopole

Preselection Filter:

137.5 MHz, insertion loss: 1.2 dB, 3-dB bw: 4.1 MHz, 40-dB bw: 24.6 MHz

402.5 MHz, insertion loss: 0.5 dB, 3-dB bw: 20.0 MHz, 40-dB bw: 68.0 MHz

761.0 MHz, insertion loss: 0.3 dB, 3-dB bw: 30.0 MHz, 40-dB bw: 102.0 MHz

Preamplifier (cascaded component specifications)

Amplifier: gain: 37 dB, noise figure: 1.4 dB, 1 dB compression point: 10 dBm

Attenuator: loss: 6 dB

Amplifier: gain: 24 dB, noise figure: 4.5 dB, 1 dB compression point: 25 dBm

Attenuator: loss: 10 dB

Cable, RG 58/U

137.5 MHz, insertion loss: 0.055 dB/ft.

402.5 MHz, insertion loss: 0.10 dB/ft

761.0 MHz, insertion loss: 0.145 dB/ft

Spectrum Analyzer

Attenuation: 0 dBm

Reference level: -10 dBm

Resolution filter noise equivalent bandwidth: 36 kHz

Resolution filter bandwidth: 30 kHz

Video filter 3-dB bandwidth: 3 MHz

Single sweep mode

Zero span mode

Noise figure: 35 dB

1 dB compression point: -5 dBm

Log amplifier output: 0.1 volt DC to 1.0 volt DC output corresponding to -100 dBm 

to -10 dBm input

Analog-to-Digital Converter

Resolution: 12 bit

Gain: 10

A.2 Receiver Specifications

Noise floor: -129.2 dBm

Noise figure: 2.2 dB

1 dB compression point: -50.8 dBm

3rd order intercept: 14.9 dBm

Gain: 43.5 dB

Linear dynamic range: 78.4 dB

2nd order dynamic range: 43.5 dB

3rd order dynamic range: 65.9 dB