NTIA Report TR-10-466

Emission Measurements of a Cellular 

and PCS Jammer at a Prison Facility

Frank H. Sanders

Robert T. Johnk

NTIA Report TR-10-466

Emission Measurements of a Cellular 

and PCS Jammer at a Prison Facility

Frank H. Sanders

Robert T. Johnk

U.S. DEPARTMENT OF COMMERCE

Lawrence E. Strickling

Assistant Secretary for Communications and Information

May 2010

iii

ACKNOWLEDGMENT

The authors wish to thank the Bureau of Prisons (BOP), and particularly Mr. Sterling Bryan, for 

providing access to, and coordinating the use of, the BOP facility at Cumberland, Maryland 

where these measurements were performed. Other personnel at the facility who were 

instrumental in making these measurements a success, and without whose support the work 

could not have been completed, were Warden J. D. Whitehead and two staffers, William 

McMillan and Bruce Bothast. McMillan and Bothast were instrumental in the installation, 

operation, and removal of the jammer. The authors also thank NTIA engineers of the Institute for 

Telecommunication Sciences (ITS) Theory Division, Robert Achatz, Roger Dalke and John 

Lemmon, for very valuable analysis and discussions regarding the detector responses of 

spectrum analyzer measurement circuitry to swept-frequency signal inputs. Their insights on this 

subject ensured the technical strength and reliability of the results that are presented in this 

report.

DISCLAIMER

Some technical information regarding the cellular jammer that NTIA measured may be 

considered intellectual property by the manufacturer of the device. The device descriptions that 

this report provides, its operational parameters, and its emissions are provided solely for the 

purpose of evaluating what engineering impact, if any, the possible future operation of the device 

might have on other systems that use the radio spectrum. The device that is described herein is 

not FCC-certified, nor does a certified standard design or operational configuration for it exist.

Some test and measurement equipment are identified in this report for the purpose of 

comprehensively describing the methodology and results of the work that NTIA performed. Such 

identification does not imply endorsement by the Department of Commerce of the equipment so 

identified, nor does such identification imply that the equipment was the only possible choice for 

adequate performance of such tests and measurements.

v

CONTENTS

Page

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

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

ABBREVIATIONS/ACRONYMS.................................................................................ix

EXECUTIVE SUMMARY ............................................................................................ xi

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

1.1 Objective .............................................................................................................. 1

1.2 Approach.............................................................................................................. 2

2 JAMMER INSTALLATION, MEASUREMENT SYSTEM, AND DATA 

DESCRIPTION.................................................................................................. 3

2.1 Jammer Installation............................................................................................... 3

2.2 Jammer Technical Characteristics......................................................................... 4

2.3 NTIA Spectrum Measurement System.................................................................. 4

2.3.1 Measurement System Antenna........................................................................ 4

2.3.2 Spectrum Analyzer Measurement Parameters ................................................. 5

2.3.3 Measurement Control Software....................................................................... 6

2.4 Measurement Locations........................................................................................ 6

3 MEASUREMENT RESULTS AND ANALYSIS........................................................ 8

3.2 Measurement Results............................................................................................. 8

3.2 Power Units in Data Plots...................................................................................... 8

3.3 Analysis of Measurement Results........................................................................ 22

4 SUMMARY.............................................................................................................. 23

5 REFERENCES.......................................................................................................... 25

APPENDIX A. JAMMER EMISSIONS MEASURED IN 1 MHZ BANDWIDTH ...... 26

APPENDIX B. POWER UNIT CONVERSIONS......................................................... 37
vi

FIGURES

Page

Figure 1. Schematic representation of the interior jammer installation.............................3

Figure 2. Overhead view of the area outside the targeted jamming zone 

and the exterior measurement locations. ..........................................................................7

Figure 3. Inside jamming zone, Point I-1 (first floor, west end), cellular band. ................9

Figure 4. Inside jamming zone, Point I-1 (first floor, west end), PCS band. .....................9

Figure 5. Inside jamming zone, Point I-2 (first floor, east end), cellular band................. 10

Figure 6. Inside jamming zone, Point I-2 (first floor, east end), PCS band. .................... 10

Figure 7. Inside jamming zone, Point I-3 (second floor, west end), cellular band........... 11

Figure 8. Inside jamming zone, Point I-3 (second floor, west end), PCS band................ 11

Figure 9. Inside jamming zone, Point I-4 (second floor, east end), cellular band............ 12

Figure 10. Inside jamming zone, Point I-4 (second floor, east end), PCS band............... 12

Figure 11. Beyond jamming zone, Point O-1 (26 m from center), cellular band............. 13

Figure 12. Beyond jamming zone, Point O-1 (26 m from center), PCS band.................. 13

Figure 13. Beyond jamming zone, Point O-2 (35 m from center,) cellular band............. 14

Figure 14. Beyond jamming zone, Point O-2 (35 m from center), PCS band.................. 14

Figure 15. Beyond jamming zone, Point O-3 (37 m from center), cellular band............. 15

Figure 16. Beyond jamming zone, Point O-3 (37 m from center), PCS band.................. 15

Figure 17. Beyond jamming zone, Point O-4 (87 m from center), cellular band............. 16

Figure 18. Beyond jamming zone, Point O-4 (87 m from center), PCS band.................. 16

Figure 19. Beyond jamming zone, Point O-5 (131 m from center), cellular band........... 17

Figure 20. Beyond jamming zone, Point O-5 (131 m from center), PCS band................ 17

Figure 21. Beyond jamming zone, Point O-6 (52 m, non-LOS), cellular band................ 18
vii

Figure 22. Beyond jamming zone, Point O-6 (52 m, non-LOS), PCS band. ................... 18

Figure 23. Beyond jamming zone, Point O-7 (74 m, non-LOS), cellular band................ 19

Figure 24. Beyond jamming zone, Point O-7 (74 m, non-LOS), PCS band. ................... 19

Figure 25. Measured power at Point O-1, 162-174 MHz................................................ 20 

Figure 26. Measured power at Point O-1, 406-420 MHz................................................ 20

Figure 27. Measured power at Point O-1, 1176 MHz..................................................... 21

Figure 28. Measured power at PointO- 1, 1227 MHz..................................................... 21

Figure 29. Measured power at Point O-1, 1575 MHz..................................................... 22

Figure A-1. Inside jamming zone, Point I-1 (first floor, west end), cellular band. .......... 26

Figure A-2. Inside jamming zone, Point I-1 (first floor, west end), PCS band................ 26

Figure A-3. Inside jamming zone, Point I-2 (first floor, east end), cellular band. ........... 27

Figure A-4. Inside jamming zone, Point I-2 (first floor, east end), PCS band. ................ 27

Figure A-5. Inside jamming zone, Point I-3 (second floor, west end), cellular band....... 28

Figure A-6. Inside jamming zone, Point I-3 (second floor, west end), PCS band............ 28

Figure A-7. Inside jamming zone, Point I-4 (second floor, east end), cellular band........ 29

Figure A-8. Inside jamming zone, Point I-4 (second floor, east end), PCS band............. 30

Figure A-9. Beyond jamming zone, Point O-1 (26 m from center), cellular band........... 30

Figure A-10. Beyond jamming zone, Point O-1 (26 m from center), PCS band.............. 31

Figure A-11. Beyond jamming zone, Point O-2 (35 m from center), cellular band......... 31

Figure A-12. Beyond jamming zone, Point O-2 (35 m from center), PCS band.............. 32

Figure A-13. Beyond jamming zone, Point O-3 (37 m from center), cellular band......... 32

Figure A-14. Beyond jamming zone, Point O-3 (37 m from center), PCS band.............. 32

Figure A-15. Beyond jamming zone, Point O-4 (87 m from center), cellular band......... 33
viii

Figure A-16. Beyond jamming zone, Point O-4 (87 m from center), PCS band.............. 33

Figure A-17. Beyond jamming zone, Point O-5 (131 m from center), cellular band....... 34

Figure A-18. Beyond jamming zone, Point O-5 (131 m from center), PCS band............ 34

Figure A- 19. Beyond jamming zone, Point O-6 (52 m, non-LOS), cellular band........... 35

Figure A-20. Beyond jamming zone, Point O-6 (52 m, non-LOS), PCS band. ............... 35

Figure A-21. Beyond jamming zone, Point O-7 (74 m, non-LOS), cellular band............ 36

Figure A-22. Beyond jamming zone, Point O-7 (74 m, non-LOS), PCS band. ............... 36

TABLES

Page

Table 1. Jammer Transmitter Characteristics. .................................................................4

Table 2. Measurement Parameters for In-Situ Prison Emission Measurements. ...............5

Table 3. Measurement Locations and Data-Figure Index. ...............................................6
ix

ABBREVIATIONS/ACRONYMS

ARA Antenna Research Associates company

BOP Federal Bureau of Prisons

EIRP effective isotropic radiated power

GPS Global Positioning System

IF intermediate frequency (stage of a radio receiver)

ITS Institute for Telecommunication Sciences, NTIA, U.S. Department of

Commerce

LMR land mobile radio

LOS line-of-sight

NIST National Institute of Standards and Technology (of the U.S. Department of

Commerce)

NTIA National Telecommunications and Information Administration (of the

U.S. Department of Commerce)

OSM Office of Spectrum Management, NTIA, U.S. Department of Commerce

PCS Personal Communication Service

RF radiofrequency

RMS root mean square (average power detection)

STA Special Temporary Authority (for a radio transmission)
x
xi

EXECUTIVE SUMMARY

This report describes National Telecommunications and Information Administration 

(NTIA) emission spectrum measurements of a cellular and Personal Communication 

Service (PCS) jamming system that was operated under a Special Temporary 

Authorization (STA) at a Federal Bureau of Prisons (BOP) minimum-security facility at 

Cumberland, MD.1 NTIA assisted with the STA and agency-level coordination of the 

installation between BOP and the manufacturer, but did not participate in the installation 

itself, which BOP personnel performed with on-site inputs from the manufacturers’ 

representatives. BOP personnel operated the jammer during the measurements.

The jammer emissions were transmitted entirely indoors. The targeted jamming zone was 

the interior of a two-floor reinforced cinderblock structure measuring 30 meters (m) long 

by 8 m wide. Jammer emissions were measured both indoors and outdoors, that is, both 

inside and outside the targeted jamming zone. Each measurement was repeated twice, 

once with the jammer on and once with the jammer off, so as to show clearly the relative 

levels of the jammer emissions and the ambient cellular and PCS signal levels at each 

measurement location.

NTIA performed measurements at four indoor and seven outdoor locations. At the indoor 

locations, measured differences in power between when the jammer was on versus off 

showed that cellular and PCS signal power levels were measurable and jammer power 

was much greater than either the cellular or PCS levels. For the outdoor locations where 

jamming was not intended, the results showed that jammer power was measurable at 

distances up to 127 m from the building. However, the differences in power between 

when the jammer was on and off were not as large as were observed for the indoor 

locations. Analysis of the in-band (cellular and PCS) potential for harmful interference, if 

any, of the jammer emissions that were observed outside the jamming zone was beyond 

the scope of this report. Jammer signal power levels were below measurable levels at the 

outdoor locations within the Federal land mobile radio (LMR) and Global Positioning 

System (GPS) bands of 162-174 MHz, 406-420 MHz, 1164-1188 MHz, 1215-1240 MHz, 

and 1559-1610 MHz.

The measurement results of this study are idiosyncratic to this particular jammer 

installation and facility. Variations in jammer characteristics, structural characteristics of 

buildings, and propagation factors will produce different results for different installations 

at different facilities.

 1 NTIA measured broadband (100-6000 MHz) spectrum emissions of the jammer earlier inside an 

anechoic chamber in Boulder, Colorado [1]. While the jammer was the same unit as had earlier 

been measured, the manufacturer used different radiofrequency (RF) filtering for out-of-band and 

spurious spectrum control than had been supplied for the measurements in the chamber. The 

change in RF filtering is not believed to have affected the results of the measurements at the BOP 

facility relative to the anechoic chamber data, because the measurements at the BOP facility were 

mostly performed on in-band and adjacent-band jammer emissions.
xii

THIS PAGE INTENTIONALLY LEFT BLANK
EMISSION MEASUREMENTS OF A CELLULAR AND PCS JAMMER

AT A PRISON FACILITY

Frank H. Sanders and Robert T. Johnk2

This report describes emission-spectrum measurements of a denial-of-service 

(jammer) transmitter that was operated temporarily in 800 MHz and 

1900 MHz cellular and PCS bands at a prison location. The jammer targeted 

signals indoors within a minimum-security facility operated by the Federal 

Bureau of Prisons. Spectrum measurements of the jammer emissions were 

performed inside and outside the targeted jamming zone with multiple 

measurement bandwidths and detectors, both in-band and in selected Federal 

land mobile radio and GPS spectrum bands. Measurements at each location 

were performed with the jammer on versus off so as to show the relative 

power levels of the jamming signal and the ambient cellular and PCS signals 

at each location. In-band jammer emissions were measured outside the 

targeted zone at distances of up to 127 m from the edge of the targeted zone.

Key words: cellular communications jamming; denial-of-service jamming; 

emission bandwidth; harmful interference; in-band emissions; personal 

communication service (PCS) communications jamming; radio jamming

1 INTRODUCTION

For correctional facilities in the United States, parties have proposed to operate radio 

transmitters that produce intentional denial-of-service (jammer) emissions in the base 

station transmitter frequency bands of 869-894 MHz (cellular band) and 1930-1990 MHz 

(PCS band).3 This report describes the results of measurements that the National 

Telecommunications and Information Administration (NTIA) Institute for 

Telecommunication Sciences (ITS) laboratory performed on radio spectrum emissions 

produced by one such jammer transmitter that was operated temporarily at a minimumsecurity prison operated by the Federal Bureau of Prisons (BOP).

1.1 Objective

The objective of this study was to perform emission spectrum measurements on jammer 

signals inside and outside a jamming zone at a BOP facility at Cumberland, Maryland.

 2 The authors are with the Institute for Telecommunication Sciences, National 

Telecommunications and Information Administration (NTIA), U.S. Department of Commerce, 

Boulder, CO.

3 For brevity, this report refers to the 869-894 MHz and 1930-1990 MHz frequency bands as the 

800 MHz and 1900 MHz bands, respectively.
2

1.2 Approach

The study approach was:

1) An experimental Special Temporary Authority (STA) to transmit the jamming 

signal was obtained by NTIA.

2) The manufacturer of the jammer, with BOP cooperation, installed the jammer 

inside a minimum-security building. NTIA participated in the site selection 

process and assisted in coordination of the use of the site between the BOP and 

the manufacturer, but did not participate in or direct any aspect of the jammer 

installation or configuration.

3) NTIA personnel performed a hardline-coupled measurement of the power 

generated by the jammer transmitter and used this data to determine the effective 

isotropic radiated power (EIRP) of the jammer signal.

4) NTIA personnel used a portable measurement system to measure the in-band and 

adjacent-band emission levels. The jammer was turned on and off for each 

measurement, so as to allow ambient cellular and PCS signal levels to be 

measured separately from the jammer emissions. Measurements were performed 

at four locations inside the targeted jamming zone (inside the building), and at 

seven locations outside the zone (outdoors). Five of the outdoor locations had 

line-of-sight (LOS) propagation to the building; two did not. Distances ranged 

between 26 m to 131 m from the center of the building.

5) NTIA reduced the spectrum measurement data to graphical plots, which are 

provided in this report. These data show the field-strength emission levels (in 

units of decibels relative to a microvolt per meter, or dBμV/m) of the jammer 

inside and outside the targeted jamming zone as a function of location and of the 

measurement bandwidth and signal detection technique. The relative levels of the 

jammer signal and the ambient cellular and PCS signals are shown in each data 

graph.
3

2 JAMMER INSTALLATION, MEASUREMENT SYSTEM, AND DATA 

DESCRIPTION

2.1 Jammer Installation

The configuration of the jammer transmitter and its antenna array inside the building 

where it was installed is shown in Figure 1. The figure is schematic and the building 

dimensions are approximate.

Figure 1. Schematic representation of the interior jammer installation (orange) and 

spectrum measurement locations (blue). Top: exterior view with approximate window 

layout. Bottom: Interior view. SA = spectrum analyzer; PC = PC laptop computer. The 

four measurement locations are indexed as I-1 through I-4.

The building construction was cinderblock with internal steel reinforcement. The 

approximate building dimensions were 30 m long by 8 m wide by two floors high. The 

building had a number of exterior windows. The jammer antennas were installed above 

the two interior ceilings along the building’s central hallway axis. The ceiling heights 

were about 2.5 m above each floor. The jammer antennas were omnidirectional and were 

of the same model as an omni antenna that was used during previous NTIA anechoic 

chamber emission measurements of the jammer emission spectra [1].
4

2.2 Jammer Technical Characteristics

The jammer transmitter was the same physical unit as was used for emissioncharacteristics measurements that had been performed in an anechoic chamber in 

Boulder, Colorado [1]. The jammer transmitter characteristics are listed in Table 1.

Table 1. Jammer Transmitter Characteristics.

Chirp 

Frequency 

Range

(MHz)

Chirp Time

(μs)

Chirp 

Rate

(MHz/μs)

Spectrum 

Line Spacing

(kHz)

Transmitter 

Output Power

(W)

869-894 5.1 4.9 196 100

1930-1990 20.4 2.9 49 100

The jammer output filtering differed from the diplexer that was used as an out-of-band 

filter for the anechoic chamber measurements [1]. The filters that were used for the 

prison installation are not believed to have affected the outcome of the measurements in 

this study, as these measurements were within the filter passbands (i.e., in-band).

The power level of the jammer transmitter output was measured directly, via a hardline 

connection to a precision power meter, at +53 dBm for the two bands combined. This is 

200 W, or 100 W (+50 dBm) per jammer band assuming the same 50/50 band split as 

was observed in earlier anechoic chamber measurements [1]. There was 5 dB of filtering 

loss and 3 dB of cable loss in the jamming system. The 8 dB of filtering and cable losses 

meant that a total of (+50 dBm – 8 dB) = +42 dBm or 15.8 W of power was delivered per 

band to the combination of four jammer antennas.4 With an approximate gain of 0 dBi for 

the radiating antennas, the EIRP of the entire jammer system inside the building was 

therefore +42 dBm = +12 dBW = 15.8 W per band.

2.3 NTIA Spectrum Measurement System

The NTIA measurement system consisted of a broadband antenna, a spectrum analyzer, 

and a laptop PC control computer that was used to control the spectrum analyzer and 

record data. The measurement system and its parameters are described below.

2.3.1 Measurement System Antenna

The measurement antenna was an omnidirectional Antenna Research Associates (ARA) 

100 MHz-2000 MHz spiky discone, model SAS-2201C. The antenna was passive (that is, 

it did not incorporate a front-end low-noise amplifier). Its gain in the cellular and PCS 

 4 The EIRP radiated by each of the four antennas was 1⁄4 of +42 dBm per band, which was 

therefore (42 – 6) dBm = +36 dBm, or approximately 4 W per antenna per band.
5

bands was -1 dB relative to isotropic.5 For indoor measurements, the antenna was 

mounted on a non-conductive tripod and was connected to the spectrum analyzer by a 

short length of low-loss radio frequency (RF) line. For outdoor measurements, the 

antenna was mounted on the roof of the NTIA Radio Spectrum Measurement System 

model 3 (RSMS-3). The antenna was mounted 1 m above floor level indoors and 3 m 

above ground level outdoors.

2.3.2 Spectrum Analyzer Measurement Parameters

The spectrum analyzer was a portable Agilent E4407B. It was operated with its RF frontend preamplifier turned off and zero RF attenuation at the input. The analyzer’s 

intermediate frequency (IF) reference level was -20 dBm for 100 kHz measurement 

bandwidth and -10 dBm for 1 MHz measurement bandwidth. The spectrum analyzer data 

traces each contained 1001 frequency bins. The data presented in this report were 

collected in the cellular and PCS bands using the measurement parameters shown in 

Table 2.

Table 2. Measurement Parameters for In-Situ Prison Emission Measurements.

Freq. 

Range

(MHz)6

IF Stage 

(Resolution) 

Bandwidth

(kHz)

Video 

Bandwidth

(kHz)

Detection

Sweep 

Time

(sec)

Freq. 

Bin Size 

(kHz)

Dwell 

per Bin 

(μs)

Jammer 

Sweeps 

per Bin

860-900 100 300 Peak 0.1 40 100 19.6

860-900 100 1 Average 1 40 1000 196

860-900 1000 3000 Peak 0.1 40 100 19.6

1920-2000 100 300 Peak 0.1 80 100 4.9

1920-2000 100 1 Average 2 80 2000 98

1920-2000 1000 3000 Peak 0.1 80 100 4.9

In the cellular and PCS bands, both peak and average data were acquired in a 100 kHz 

measurement bandwidth, and additional peak data were acquired in a 1 MHz bandwidth. 

Peak-power measurements were performed with the analyzer in a maximum-hold trace 

mode for a total of 10 traces. In this mode, the analyzer’s peak detector latches to the 

highest level that occurs within each sampling interval for each spectrum analyzer 

frequency bin (see the last three columns in Table 2), and the maximum-hold trace mode 

latches to the highest power level in each spectrum analyzer frequency-measurement bin 

over a series of frequency sweeps. Thus the maximum-hold, peak measurements show 

the highest power level that occurs in the measurement bandwidth at each frequency in 

the measured spectrum. Average power was measured by setting the video average filter 

bandwidth to a fraction of the width of the resolution bandwidth filter, setting the dwell 

 5 From a custom calibration by the ARA company.

6 The measurement band edges were set somewhat wider than the 869-894 MHz and 1930-

1990 MHz cellular and PCS band edges so that adjacent-band roll-off of the jammer emissions 

could be observed in the measurement data.
6

time in each frequency bin to be much larger than the reciprocal bandwidth of the video 

average filter, and sampling the output of the video average filter once per frequency bin.

Additional spectrum measurements were performed in two Federal land mobile radio 

(LMR) bands (162-174 MHz, 406-420 MHz), and three GPS bands (centered around 

1176 MHz, 1227 MHz, and 1575 MHz). These data were acquired with a 10 kHz 

bandwidth in the LMR bands, so as to match typical LMR receiver bandwidths, and in a 

1 MHz reference bandwidth in the GPS bands.

2.3.3 Measurement Control Software

The spectrum analyzer was controlled by a laptop computer running NTIA dataacquisition (DA) software [2]. The DA software was configured prior to the measurement

to automatically run the measurements shown in Table 2. The software ran each of the 

measurements listed in Table 2 twice, once with the jammer on and once with the jammer 

off, so that the jammer emissions could be compared to the ambient cellular and PCS 

signal-power levels.

2.4 Measurement Locations

As shown in Figure 1, four measurement locations were used inside the building (the 

targeted jamming zone), two on the first floor and two on the second floor. These are 

designated I (for interior) 1-4. The rooftop of the targeted building and the outdoor 

measurement locations are shown in Figure 2. The outdoor locations are designated O 

(for outdoor) 1-7. The measurement locations are summarized in Table 3.

Table 3. Measurement Locations and Data-Figure Index.

Data Point 

Identifier 

and Location

Figure Numbers 

Showing Emission 

Data

Distance from 

Center of Targeted 

Zone (m)

Distance from 

Edge of Targeted 

Zone (m)

Line-ofSight 

(LOS)

I-1 (Fig. 1) 3, 4, A-1, A-2 Inside Inside Inside

I-2 (Fig. 1) 5, 6, A-3, A-4 Inside Inside Inside

I-3 (Fig. 1) 7, 8, A-5, A-6 Inside Inside Inside

I-4 (Fig. 1) 9, 10, A-7, A-8 Inside Inside Inside

O-1 (Fig. 2) 11, 12, A-9, A-10 26 22 yes

O-2 (Fig. 2) 13, 14, A-11, A-12 35 30 yes

O-3 (Fig. 2) 15, 16, A-13, A-14 37 33 yes

O-4 (Fig. 2) 17, 18, A-15, A-16 87 83 yes

O-5 (Fig. 2) 19, 20, A-17, A-18 131 127 yes

O-6 (Fig. 2) 21, 22, A-19, A-20 52 47 no

O-7 (Fig. 2) 23, 24, A-21, A-22 74 69 no
7

Figure 2. Overhead view of the area outside the targeted jamming zone and the exterior 

measurement locations. Clear line-of-sight (LOS) coverage existed between the building 

and measurement system for locations O-1 through O-5; obstructions existed between the 

building and the measurement system for locations O-6 and O-7.
8

3 MEASUREMENT RESULTS AND ANALYSIS

3.1 Measurement Results

Figures 3-24 depict measurements made in the 100 kHz bandwidth. Progressing from the 

highest-power to lowest-power trace in each figure, these are: positive-peak detected with 

the jammer on (red), average-detected with the jammer on (black), positive-peak detected 

with the jammer off (green), and average-detected with the jammer off (blue). The data in 

Figures 25-29 are peak-detected only; each of those graphs consists of a single trace 

showing only the background signals in the vicinity of the prison. Additional data, 

measured in a 1 MHz bandwidth, are provided in Appendix A.

3.2 Power Units in Data Plots

The raw data were collected in units of decibels relative to a milliwatt (dBm). The power 

units in Figures 3-24 and Appendix A have been converted into logarithmic field strength 

(decibels relative to a microvolt per meter, or dBμV/m). The conversion math is given in 

Appendix B. 

Unlike the jammer emission data that were presented in [1] in terms of EIRP, the data in 

Figures 3-24 cannot be graphed in such units because EIRP calculations require that the 

distance to a transmitter must be known, and the distances to the local cellular and PCS 

towers are not known. Moreover, their EIRP levels would differ from the EIRP levels of 

the jammer emissions. Since the cellular and PCS levels need to be placed on the same 

graphs for comparative purposes, it is not possible to put the data in these graphs into 

terms of EIRP.

The data in the LMR and GPS bands (Figures 25-29) are plotted in units of dBm. This is 

because the spectra in the bands shown in those figures (the land mobile radio (LMR) 

bands162-174 MHz and 406-420 MHz, and the Global Positioning System (GPS) bands 

around 1176 MHz, 1227 MHz, and 1575 MHz) contain no observable jammer emissions. 

The data in these plots are a null result: only the noise limit of the measurement system 

(the noise in the spectrum analyzer) is in the plots (plus a few ambient, non-jammer 

signals). Field strength in free space would not refer to a measured power level, but 

would instead be only be an upper limit on the possible jammer power level in these 

bands at the location where these data were measured.
9

Figure 3. Inside jamming zone, Point I-1 (first floor, west end), cellular band.

Figure 4. Inside jamming zone, Point I-1 (first floor, west end), PCS band.
10

Figure 5. Inside jamming zone, Point I-2 (first floor, east end), cellular band.

Figure 6. Inside jamming zone, Point I-2 (first floor, east end), PCS band.
11

Figure 7. Inside jamming zone, Point I-3 (second floor, west end), cellular band.

Figure 8. Inside jamming zone, Point I-3 (second floor, west end), PCS band.
12

Figure 9. Inside jamming zone, Point I-4 (second floor, east end), cellular band.

Figure 10. Inside jamming zone, Point I-4 (second floor, east end), PCS band.
13

Figure 11. Beyond jamming zone, Point O-1 (26 m from center), cellular band.

Figure 12. Beyond jamming zone, Point O-1 (26 m from center), PCS band.
14

Figure 13. Beyond jamming zone, Point O-2 (35 m from center,) cellular band.

Figure 14. Beyond jamming zone, Point O-2 (35 m from center), PCS band.
15

Figure 15. Beyond jamming zone, Point O-3 (37 m from center), cellular band.

Figure 16. Beyond jamming zone, Point O-3 (37 m from center), PCS band.
16

Figure 17. Beyond jamming zone, Point O-4 (87 m from center), cellular band.

Figure 18. Beyond jamming zone, Point O-4 (87 m from center), PCS band.
17

Figure 19. Beyond jamming zone, Point O-5 (131 m from center), cellular band.

Figure 20. Beyond jamming zone, Point O-5 (131 m from center), PCS band.
18

Figure 21. Beyond jamming zone, Point O-6 (52 m, non-LOS), cellular band.

Figure 22. Beyond jamming zone, Point O-6 (52 m, non-LOS), PCS band.
19

Figure 23. Beyond jamming zone, Point O-7 (74 m, non-LOS), cellular band.

Figure 24. Beyond jamming zone, Point O-7 (74 m, non-LOS), PCS band.
20

Figure 25. Measured power at Point O-1, 162-174 MHz, no jammer emission observable. 

A weather service signal is observed.

Figure 26. Measured power at Point O-1, 406-420 MHz, no jammer emission observable. 

Two local land mobile radio signals are observed.
21

Figure 27. Measured power at Point O-1, 1176 MHz, no jammer emission observable.

Figure 28. Measured power at Point O- 1, 1227 MHz, no jammer emission observable. 

The hump at 1224.7 MHz is not a jammer emission.
22

Figure 29. Measured power at Point O-1, 1575 MHz, no jammer emission observable.

3.3 Analysis of Measurement Results

At the indoor locations, measured differences in power between when the jammer was on 

versus off indicated that cellular and PCS signal power levels were measurable and 

jammer power was much greater than either. For the outdoor locations where jamming 

was not intended, the results showed that jammer power was measurable at distances up 

to 127 m from the building (131 from the center of the building). However, the 

differences in power between when the jammer was on and off were not as large as were 

observed for the indoor locations. Analysis of the in-band (cellular and PCS) potential for 

harmful interference, if any, of the jammer emissions that were observed outside the 

jamming zone was beyond the scope of this report. Given that the jammer’s transmitted 

in-band power levels were constant with frequency [1], the in-band variations in power 

level as a function of frequency that were observed in the measurements in this report are 

believed to be due to frequency-dependent effects of multipath propagation, building 

penetration, and diffraction. Measurements of jammer emissions at other facilities would 

produce different results.

Jammer signal power levels were below measurable levels at the outdoor locations within 

the Federal land mobile radio (LMR) and Global Positioning System (GPS) bands of 

162-174 MHz, 406-420 MHz, 1164-1188 MHz, 1215-1240 MHz, and 1559-1610 MHz.
23

4 SUMMARY

1) The same jammer system as was measured earlier in an anechoic chamber in Boulder, 

Colorado was temporarily installed and operated under an STA in cellular and PCS 

bands at a minimum-security Federal prison at Cumberland, Maryland. The building 

construction was of steel-reinforced cinderblock, two floors in height, with windows 

in the exterior walls. The jammer installation was intended to block reception of 

cellular and PCS signals inside the building while not causing harmful interference to 

such signals outside the building.

2) The EIRP of the jammer system in each band (cellular and PCS) was +42 dBm = 

+12 dBW = 15.8 W. This EIRP was radiated via a set of four omnidirectional 

antennas, two per floor, located above each of the floors’ respective ceilings. The 

antennas that were used were of the same model as had been supplied with the 

jammer for the earlier anechoic chamber measurements.

3) NTIA performed in-band and adjacent-band measurements of the jammer emissions 

relative to the ambient cellular and PCS signal levels both inside the target jamming 

zone (the building interior) and outside the building, where jamming was not 

intended. The results of those measurements are provided in this report.

4) The jammer emissions were observed at distances up to the maximum that could be 

accessed by the measurement vehicle, at 131 m from the center of the jamming zone.

5) Inside the targeted jamming zone (the building interior), the jammer signal power 

levels exceeded the levels of the ambient cellular and PCS signals. Beyond that zone 

(outside the building, that is), the jammer signal was still measurable. The relative 

levels of the jammer signal and the ambient cellular and PCS signals varied as a 

function of distance and azimuth from the building. Non-line-of-sight paths outside 

the building showed less jammer signal power than line-of-sight paths.

6) No measurable signal power was observed outside the jamming zone in the Federal 

LMR and GPS bands of 162-174 MHz, 406-420 MHz, 1164-1188 MHz, 1215-1240 

MHz, and 1559-1610 MHz.

7) Analysis of the in-band (cellular and PCS) potential for harmful interference, if any, 

of the jammer emissions that were observed outside the jamming zone was beyond 

the scope of this report.

8) The results presented in this report are idiosyncratic to the technical particulars of this 

jammer transmitter and the building in which its signal was radiated. Different results 

would be expected for any given jammer installation at any given location.

9) For in-band measurements of chirped-frequency jammer emissions relative to 

ambient service-provider communication signals (such as cellular or PCS), it is 

recommended that the methodology used in this report should be followed. Two
24

spectrum measurements would need to be performed at each location, once with the 

jammer turned on and then repeated with the jammer turned off. This approach allows 

the jammer emissions to be measured relative to the ambient signal power levels. 

Measurements should be performed in a bandwidth commensurate with the jammer 

emission-line spacing. If the emission lines are less than 1 MHz apart, additional 

measurements in a 1 MHz reference bandwidth may also be desirable for EMC 

analyses. (In contrast, for measurements of spurious and out-of-band (OOB), or 

unwanted, jammer emission levels relative to the in-band power level of a chirpedfrequency jammer signal, the proper measurement bandwidth is equal to or slightly 

less than the square root of the ratio of the chirp-frequency range divided by the 

chirp-time interval [1].)
25

5 REFERENCES

[1] F. H. Sanders, R. T. Johnk, M. A. McFarland, and J. R. Hoffman “Emission 

measurement results for a cellular and PCS signal-jamming transmitter.” NTIA Technical 

Report 10-465, Feb. 2010. Available: http://www.its.bldrdoc.gov/pub/ntia-rpt/10-

465/index.php.

[2] F. H. Sanders, B. J. Ramsey and V. S. Lawrence, “Broadband spectrum survey at 

Los Angeles, California,” NTIA Report 97-336, May 1997. Available: 

http://www.its.bldrdoc.gov/pub/ntia-rpt/97-336/index.php.

[3] F. H. Sanders, “Conversion of power measured in a circuit to incident field 

strength and incident power density, and corrections to measured emission spectra for 

non-constant aperture measurement antennas,” Appendix C, In: W. Kissick (ed.), “The 

temporal and spectral characteristics of ultrawideband signals.” NTIA Technical Report 

01-383, Jan. 2001. Available: http://www.its.bldrdoc.gov/pub/ntia-rpt/01-383/index.php.
26

APPENDIX A. JAMMER EMISSIONS MEASURED IN 1 MHZ BANDWIDTH

Figure A-1. Inside jamming zone, Point I-1 (first floor, west end), cellular band.

Figure A-2. Inside jamming zone, Point I-1 (first floor, west end), PCS band.
27

Figure A-3. Inside jamming zone, Point I-2 (first floor, east end), cellular band.

Figure A-4. Inside jamming zone, Point I-2 (first floor, east end), PCS band.
28

Figure A-5. Inside jamming zone, Point I-3 (second floor, west end), cellular band.

Figure A-6. Inside jamming zone, Point I-3 (second floor, west end), PCS band.
29

Figure A-7. Inside jamming zone, Point I-4 (second floor, east end), cellular band.

Figure A-8. Inside jamming zone, Point I-4 (second floor, east end), PCS band.
30

Figure A-9. Beyond jamming zone, Point O-1 (26 m from center), cellular band.

Figure A-10. Beyond jamming zone, Point O-1 (26 m from center), PCS band.
31

Figure A-11. Beyond jamming zone, Point O-2 (35 m from center), cellular band.

Figure A-12. Beyond jamming zone, Point O-2 (35 m from center), PCS band.
32

Figure A-13. Beyond jamming zone, Point O-3 (37 m from center), cellular band.

Figure A-14. Beyond jamming zone, Point O-3 (37 m from center), PCS band.
33

Figure A-15. Beyond jamming zone, Point O-4 (87 m from center), cellular band.

Figure A-16. Beyond jamming zone, Point O-4 (87 m from center), PCS band.
34

Figure A-17. Beyond jamming zone, Point O-5 (131 m from center), cellular band.

Figure A-18. Beyond jamming zone, Point O-5 (131 m from center), PCS band.
35

Figure A- 19. Beyond jamming zone, Point O-6 (52 m, non-LOS), cellular band.

Figure A-20. Beyond jamming zone, Point O-6 (52 m, non-LOS), PCS band.
36

Figure A-21. Beyond jamming zone, Point O-7 (74 m, non-LOS), cellular band.

Figure A-22. Beyond jamming zone, Point O-7 (74 m, non-LOS), PCS band.
37

APPENDIX B. POWER UNIT CONVERSIONS

B.1 Power Conversion Between Measured dBm and Displayed Field Strength Units

The power units in Figures 3-24 and Appendix A are logarithmic field strength (decibels 

relative to a microvolt per meter, or dBμV/m). The raw data were collected in decibels 

relative to a milliwatt, or dBm. The conversion between these units was performed as 

follows (adapted from [3, Eq. (C.21)]):

FS = Pmeas + 77.2 + 20 log(f)! Grx , (1)

where:

FS = field strength in space of the measured signal (dBμV/m);

Pmeas = measured power in a 50-ohm circuit (dBm);

f = frequency (MHz);

Grx = gain of the receiving (measurement) antenna (dBi). Grx = -1 dBi for these 

measurements in both bands.

B.2 Conversion of Jammer Emission Field Strength to EIRP

The EIRP of the jammer emissions in the area outside the building can also be calculated. 

Using [3, Eq. (C.34)]:

EIRP = Pmeas ! Grx ! 27.5 + 20log(f)+ 20log(r,meters), (2)

and comparing Eq. (2) to Eq. (1), the EIRP is computed from the field strength as:

(EIRP,dBm)= (FS,dBμV / m)! 104.7 + 20log(r,meters) (3)

B.3 Conversion Factor for Power Density

Plotting the data in field strength provides an absolute power level in space of the jammer 

emissions and removes the effect of the measurement antenna gain from the data. Field 

strength can be converted to incident power density, if necessary [3, Eq. (C.43)]:

μW

cm

2

!

"

# $

%

& = 10

FS,dBμV /m

10

!

"

# $

%

&

377 '1010 (4)