U.S. DEPARTMENT OF COMMERCE • National Telecommunications and Information Administration

report series

NTIA Report TR-13-496 

Broadband Spectrum Survey 

in the Denver and Boulder, 

Colorado, Metropolitan Areas

Chriss Hammerschmidt

Heather E. Ottke

J. Randy Hoffman
U.S. DEPARTMENT OF COMMERCE 

August 2013 

Reissued March 2014 

NTIA Report TR-13-496 

Broadband Spectrum Survey

in the Denver and Boulder, Colorado, 

Metropolitan Areas

Chriss Hammerschmidt

Heather E. Ottke

J. Randy Hoffman

iii

NOTE ON REISSUE 

This was the first in a series of three reports presenting measurement data from three separate 

spectrum occupancy surveys carried out in 2011 and 2012 as part of ongoing research efforts. In 

preparing the third report for release, we discovered an incorrect display of the mean system 

noise and the threshold in some images. The process for generating the images was corrected and 

the images re-generated. In the reissue of this report, Figures 18, 48, 62, 63, 64, and 66 have 

been replaced with correctly generated images. The measured data was not affected by the prepublication processing and remains unchanged; only the display of the mean system noise is 

changed. 

DISCLAIMER 

Certain commercial equipment and materials are identified in this report to specify adequately 

the technical aspects of the reported tests and 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 the best available 

for this purpose. 

v

CONTENTS 

List of Figures ................................................................................................................................ vi

List of Tables ............................................................................................................................... xvi

Abbreviations/Acronyms ............................................................................................................ xvii

1 Introduction .................................................................................................................................. 1

1.1 Background ........................................................................................................................... 1

1.2 Purpose of this Survey .......................................................................................................... 2

1.3 Report Layout ....................................................................................................................... 2

2 Measurements in the Denver Metropolitan Area ......................................................................... 3

2.1 General Site Selection ........................................................................................................... 3

2.2 Denver Metropolitan Area Measurement Site Description .................................................. 4

2.3 Measurement System Description ........................................................................................ 5

3 Measured Data ........................................................................................................................... 11

3.1 Discussion of Measured Data ........................................................................................... 121

4 Acknowledgements .................................................................................................................. 130

5 References ................................................................................................................................ 131

Appendix A: Explanation of measurement graphs ..................................................................... 132

A.1 Maximum-Mean-Median-Minimum (M4) plots.............................................................. 132

A.2 Time vs. Frequency Plots ................................................................................................. 132

A.3 Field-Strength, Complementary Cumulative Distribution Function (FS-CCDF) Plots... 133

Appendix B: Radio Spectrum Measurement Sciences (RSMS) System .................................... 136

Appendix C: Static vs. Mobile measurements ............................................................................ 139

C.1 Mobile Measurements in the Denver/Boulder Metropolitan Areas ................................. 139

C.2 Mobile Measurements around the Arvada Spectrum Survey Site ................................... 144

C.3 Static Measurements at the Arvada Measurement Site .................................................... 148

C.4 Comparisons between Mobile and Static Measurements................................................. 149
vi 

LIST OF FIGURES 

Figure 1. MapQuest® map and picture showing the Arvada measurement location 

(blue triangle). ..................................................................................................................................5

Figure 2. System schematic for the LMR system and the broad-frequency system. .......................6

Figure 3. NTIA spectrum survey results from 108 to 112 MHz in Denver, CO, 

2011................................................................................................................................................14

Figure 4. NTIA spectrum survey results from 112 to 116 MHz in Denver, CO, 

2011................................................................................................................................................15

Figure 5. NTIA spectrum survey results from 116 to 120 MHz in Denver, CO, 

2011................................................................................................................................................16

Figure 6. NTIA spectrum survey results from 120 to 124 MHz in Denver, CO, 

2011................................................................................................................................................17

Figure 7. NTIA spectrum survey results from 124 to 132 MHz in Denver, CO, 

2011................................................................................................................................................18

Figure 8. NTIA spectrum survey results from 132 to 136 MHz in Denver, CO, 

2011................................................................................................................................................19

Figure 9. NTIA spectrum survey results from 136 to 138 MHz in Denver, CO, 

2011................................................................................................................................................20

Figure 10. NTIA spectrum survey results from 138 to 143 MHz in Denver, CO, 

2011................................................................................................................................................21

Figure 11. NTIA spectrum survey results from 143 to 149 MHz in Denver, CO, 

2011................................................................................................................................................22

Figure 12. NTIA spectrum survey results from 149 to 154 MHz in Denver, CO, 

2011................................................................................................................................................23

Figure 13. NTIA spectrum survey results from 154 to 159 MHz in Denver, CO, 

2011................................................................................................................................................24

Figure 14. NTIA spectrum survey results from 159 to 164 MHz in Denver, CO, 

2011................................................................................................................................................25

Figure 15. NTIA spectrum survey results from 164 to 169 MHz in Denver, CO, 

2011................................................................................................................................................26

Figure 16. NTIA spectrum survey results from 169 to 174 MHz in Denver, CO, 

2011................................................................................................................................................27
vii 

Figure 17. NTIA spectrum survey results from 174 to 192 MHz in Denver, CO, 

2011................................................................................................................................................28

Figure 18. NTIA spectrum survey results from 192 to 216 MHz in Denver, CO, 

2011................................................................................................................................................29

Figure 19. NTIA spectrum survey results from 216 to 221 MHz in Denver, CO, 

2011................................................................................................................................................30

Figure 20. NTIA spectrum survey results from 221 to 225 MHz in Denver, CO, 

2011................................................................................................................................................31

Figure 21. NTIA spectrum survey results from 225 to 237 MHz in Denver, CO, 

2011................................................................................................................................................32

Figure 22. NTIA spectrum survey results from 237 to 243 MHz in Denver, CO, 

2011................................................................................................................................................33

Figure 23. NTIA spectrum survey results from 243 to 249 MHz in Denver, CO, 

2011................................................................................................................................................34

Figure 24. NTIA spectrum survey results from 249 to 261 MHz in Denver, CO, 

2011................................................................................................................................................35

Figure 25. NTIA spectrum survey results from 261 to 273 MHz in Denver, CO, 

2011................................................................................................................................................36

Figure 26. NTIA spectrum survey results from 273 to 279 MHz in Denver, CO, 

2011................................................................................................................................................37

Figure 27. NTIA spectrum survey results from 279 to 285 MHz in Denver, CO, 

2011................................................................................................................................................38

Figure 28. NTIA spectrum survey results from 285 to 291 MHz in Denver, CO, 

2011................................................................................................................................................39

Figure 29. NTIA spectrum survey results from 291 to 297 MHz in Denver, CO, 

2011................................................................................................................................................40

Figure 30. NTIA spectrum survey results from 297 to 303 MHz in Denver, CO, 

2011................................................................................................................................................41

Figure 31.NTIA spectrum survey results from 303 to 309 MHz in Denver, CO, 

2011................................................................................................................................................42

Figure 32. NTIA spectrum survey results from 309 to 315 MHz in Denver, CO, 

2011................................................................................................................................................43
viii 

Figure 33. NTIA spectrum survey results from 315 to 321 MHz in Denver, CO, 

2011................................................................................................................................................44

Figure 34. NTIA spectrum survey results from 321 to 345 MHz in Denver, CO, 

2011................................................................................................................................................45

Figure 35. NTIA spectrum survey results from 345 to 351 MHz in Denver, CO, 

2011................................................................................................................................................46

Figure 36. NTIA spectrum survey results from 351 to 357 MHz in Denver, CO, 

2011................................................................................................................................................47

Figure 37. NTIA spectrum survey results from 357 to 363 MHz in Denver, CO, 

2011................................................................................................................................................48

Figure 38. NTIA spectrum survey results from 363 to 369 MHz in Denver, CO, 

2011................................................................................................................................................49

Figure 39. NTIA spectrum survey results from 369 to 393 MHz in Denver, CO, 

2011................................................................................................................................................50

Figure 40. NTIA spectrum survey results from 393 to 406 MHz in Denver, CO, 

2011................................................................................................................................................51

Figure 41. NTIA spectrum survey results from 406 to 411 MHz in Denver, CO, 

2011................................................................................................................................................52

Figure 42. NTIA spectrum survey results from 411 to 416 MHz in Denver, CO, 

2011................................................................................................................................................53

Figure 43. NTIA spectrum survey results from 416 to 420 MHz in Denver, CO, 

2011................................................................................................................................................54

Figure 44. NTIA spectrum survey results from 420 to 444 MHz in Denver, CO, 

2011................................................................................................................................................55

Figure 45. NTIA spectrum survey results from 420 to 450 MHz in Denver, CO, 

2011. This measurement was taken using the stepped-spectrum measurement 

algorithm. .......................................................................................................................................56

Figure 46. NTIA spectrum survey results from 444 to 468 MHz in Denver, CO, 

2011................................................................................................................................................57

Figure 47. NTIA spectrum survey results from 468 to 476 MHz in Denver, CO, 

2011................................................................................................................................................58

Figure 48. NTIA spectrum survey results from 476 to 500 MHz in Denver, CO, 

2011................................................................................................................................................59
ix

Figure 49. NTIA spectrum survey results from 500 to 524 MHz in Denver, CO, 

2011................................................................................................................................................60

Figure 50. NTIA spectrum survey results from 524 to 548 MHz in Denver, CO, 

2011................................................................................................................................................61

Figure 51. NTIA spectrum survey results from 548 to 572 MHz in Denver, CO, 

2011................................................................................................................................................62

Figure 52. NTIA spectrum survey results from 572 to 596 MHz in Denver, CO, 

2011................................................................................................................................................63

Figure 53. NTIA spectrum survey results from 596 to 620 MHz in Denver, CO, 

2011................................................................................................................................................64

Figure 54. NTIA spectrum survey results from 620 to 644 MHz in Denver, CO, 

2011................................................................................................................................................65

Figure 55. NTIA spectrum survey results from 644 to 668 MHz in Denver, CO, 

2011................................................................................................................................................66

Figure 56. NTIA spectrum survey results from 668 to 692 MHz in Denver, CO, 

2011................................................................................................................................................67

Figure 57. NTIA spectrum survey results from 692 to 716 MHz in Denver, CO, 

2011................................................................................................................................................68

Figure 58. NTIA spectrum survey results from 716 to 740 MHz in Denver, CO, 

2011................................................................................................................................................69

Figure 59. NTIA spectrum survey results from 740 to 763 MHz in Denver, CO, 

2011................................................................................................................................................70

Figure 60. NTIA spectrum survey results from 763 to 800 MHz in Denver, CO, 

2011................................................................................................................................................71

Figure 61. NTIA spectrum survey results from 800 to 833 MHz in Denver, CO, 

2011................................................................................................................................................72

Figure 62. NTIA spectrum survey results from 833 to 869 MHz in Denver, CO, 

2011................................................................................................................................................73

Figure 63. NTIA spectrum survey results from 869 to 902 MHz in Denver, CO, 

2011................................................................................................................................................74

Figure 64. NTIA spectrum survey results from 902 to 935 MHz in Denver, CO, 

2011................................................................................................................................................75
x

Figure 65. NTIA spectrum survey results from 902 to 928 MHz in Denver, CO, 

2011. This measurement was taken using the stepped-spectrum measurement 

algorithm. .......................................................................................................................................76

Figure 66. NTIA spectrum survey results from 935 to 962 MHz in Denver, CO, 

2011................................................................................................................................................77

Figure 67. NTIA spectrum survey results from 971 to 1000 MHz in Denver, CO, 

2011................................................................................................................................................78

Figure 68. NTIA spectrum survey results from 1000 to 1150 MHz in Denver, CO, 

2011................................................................................................................................................79

Figure 69. NTIA spectrum survey results from 1150 to 1300 MHz in Denver, CO, 

2011................................................................................................................................................80

Figure 70. NTIA spectrum survey results from 1300 to 1400 MHz in Denver, CO, 

2011................................................................................................................................................81

Figure 71. NTIA spectrum survey results from 1215 to 1390 MHz in Denver, CO, 

2011. This measurement was taken using the stepped-spectrum measurement 

algorithm. .......................................................................................................................................82

Figure 72. NTIA spectrum survey results from 1400 to 1450 MHz in Denver, CO, 

2011................................................................................................................................................83

Figure 73. NTIA spectrum survey results from 1450 to 1600 MHz in Denver, CO, 

2011................................................................................................................................................84

Figure 74. NTIA spectrum survey results from 1600 to 1750 MHz in Denver, CO, 

2011................................................................................................................................................85

Figure 75. NTIA spectrum survey results from 1750 to 1900 MHz in Denver, CO, 

2011................................................................................................................................................86

Figure 76. NTIA spectrum survey results from 1900 to 2000 MHz in Denver, CO, 

2011................................................................................................................................................87

Figure 77. NTIA spectrum survey results from 2000 to 2100 MHz in Denver, CO, 

2011................................................................................................................................................88

Figure 78. NTIA spectrum survey results from 2100 to 2250 MHz in Denver, CO, 

2011................................................................................................................................................89

Figure 79. NTIA spectrum survey results from 2250 to 2400 MHz in Denver, CO, 

2011................................................................................................................................................90
xi

Figure 80. NTIA spectrum survey results from 2400 to 2550 MHz in Denver, CO, 

2011................................................................................................................................................91

Figure 81. NTIA spectrum survey results from 2550 to 2700 MHz in Denver, CO, 

2011................................................................................................................................................92

Figure 82. NTIA spectrum survey results from 2700 to 2900 MHz in Denver, CO, 

2011. This measurement was taken using the stepped-spectrum measurement 

algorithm. .......................................................................................................................................93

Figure 83. NTIA spectrum survey results from 2900 to 3050 MHz in Denver, CO, 

2011................................................................................................................................................94

Figure 84. NTIA spectrum survey results from 3050 to 3150 MHz in Denver, CO, 

2011................................................................................................................................................95

Figure 85. NTIA spectrum survey results from 3150 to 3300 MHz in Denver, CO, 

2011................................................................................................................................................96

Figure 86. NTIA spectrum survey results from 3300 to 3450 MHz in Denver, CO, 

2011................................................................................................................................................97

Figure 87. NTIA spectrum survey results from 3450 to 3550 MHz in Denver, CO, 

2011................................................................................................................................................98

Figure 88. NTIA spectrum survey results from 3550 to 3700 MHz in Denver, CO, 

2011................................................................................................................................................99

Figure 89. NTIA spectrum survey results from 3700 to 3850 MHz in Denver, CO, 

2011..............................................................................................................................................100

Figure 90. NTIA spectrum survey results from 3850 to 4000 MHz in Denver, CO, 

2011..............................................................................................................................................101

Figure 91. NTIA spectrum survey results from 4000 to 4200 MHz in Denver, CO, 

2011..............................................................................................................................................102

Figure 92. NTIA spectrum survey results from 2900 to 3650 MHz in Denver, CO, 

2011. This measurement was taken using the stepped-spectrum measurement 

algorithm. .....................................................................................................................................103

Figure 93. NTIA spectrum survey results from 4000 to 5000 MHz in Denver, CO, 

2011. This measurement was taken using the azimuth-scanning measurement 

algorithm. .....................................................................................................................................104

Figure 94. Compass centered on Arvada measurement location. The compass 

shows true north. Zero degrees on the plot is magnetic north. Proximity of Rocky 

Mountain Metropolitan Airport, DIA, and Buckley Air Force Base are shown. .........................105
xii 

Figure 95. This graph is a close-up view of Figure 92, showing radio altimeter 

signatures. ....................................................................................................................................106

Figure 96. NTIA spectrum survey results from 4400 to 5000 MHz in Denver, CO, 

2011. This measurement was taken using the swept-spectrum measurement 

algorithm. .....................................................................................................................................107

Figure 97. NTIA spectrum survey results from 5000 to 5600 MHz in Denver, CO, 

2011. This measurement was taken using the swept-spectrum measurement 

algorithm. .....................................................................................................................................108

Figure 98. NTIA spectrum survey results from 5600 to 6200 MHz in Denver, CO, 

2011. This measurement was taken using the swept-spectrum measurement 

algorithm. .....................................................................................................................................109

Figure 99. NTIA spectrum survey results from 6200 to 7000 MHz in Denver, CO, 

2011. This measurement was taken using the swept-spectrum measurement 

algorithm. .....................................................................................................................................110

Figure 100. NTIA spectrum survey results from 5250 to 5925 MHz in Denver, 

CO, 2011. This measurement was taken using the stepped-spectrum measurement 

algorithm. .....................................................................................................................................111

Figure 101. NTIA spectrum survey results from 5925 to 7000 MHz in Denver, 

CO, 2011. This measurement was taken using the azimuth-scanning measurement 

algorithm. .....................................................................................................................................112

Figure 102. NTIA spectrum survey results from 7000 to 7500 MHz in Denver, 

CO, 2011. This measurement was taken using the swept-spectrum measurement 

algorithm. .....................................................................................................................................113

Figure 103. NTIA spectrum survey results from 7000 to 7500 MHz in Denver, 

CO, 2011. This measurement was taken using the azimuth-scanning measurement 

algorithm. .....................................................................................................................................114

Figure 104. NTIA spectrum survey results from 7500 to 8000 MHz in Denver, 

CO, 2011. This measurement was taken using the swept-spectrum measurement 

algorithm. .....................................................................................................................................115

Figure 105. NTIA spectrum survey results from 7500 to 8000 MHz in Denver, 

CO, 2011. This measurement was taken using the azimuth-scanning measurement 

algorithm. .....................................................................................................................................116

Figure 106. NTIA spectrum survey results from 8000 to 9000 MHz in Denver, 

CO, 2011. This measurement was taken using the swept-spectrum measurement 

algorithm. .....................................................................................................................................117
xiii 

Figure 107. NTIA spectrum survey results from 8000 to 9000 MHz in Denver, 

CO, 2011. This measurement was taken using the azimuth-scanning measurement 

algorithm. .....................................................................................................................................118

Figure 108. NTIA spectrum survey results from 9000 to 10000 MHz in Denver, 

CO, 2011. This measurement was taken using the swept-spectrum measurement 

algorithm. .....................................................................................................................................119

Figure 109. NTIA spectrum survey results from 8500 to 10000 MHz in Denver, 

CO, 2011. This measurement was taken using the stepped-spectrum measurement 

algorithm. .....................................................................................................................................120

Figure A-1. Complementary cumulative distribution function (CCDF) at 116.00 

MHz. ............................................................................................................................................134

Figure A-2. Inverse complementary cumulative distribution function. The percent 

probability is shown along the x-axis and the power is shown along the y-axis. ........................134

Figure A-3. Close-in view of one-dB probability spacing for median-of-five 

processed Gaussian noise shown inside the dashed rectangle for the frequency 

range from 411.2 to 411.4 MHz...................................................................................................135

Figure A-4. Close-in view of variable probability spacing for RMS-detected 

Gaussian noise shown inside the dashed rectangle for the frequency range from 

1210 to 1230 MHz. ......................................................................................................................135

Figure B-1. RSMS-4 measurement truck with mast-mounted antennas and 

preselector units. ..........................................................................................................................137

Figure B-2. Measurement equipment setup inside RSMS-4 truck. The LMR 

system makes measurements in the LMR bands and the broad-frequency systems 

measures all frequencies above 500 MHz and some bands not covered by the 

LMR bands...................................................................................................................................137

Figure B-3. Detailed schematics of the RSMS truck. ..................................................................138

Figure C-1. Mobile measurement route for Denver/Boulder Metropolitan Areas. .....................139

Figure C-2. Mobile measurements from 406 to 411 MHz in the Denver 

Metropolitan area. ........................................................................................................................141

Figure C-3. Mobile measurements from 411 to 416 MHz in the Denver 

Metropolitan area. ........................................................................................................................142

Figure C-4. Mobile measurements from 416 to 420 MHz in the Denver 

Metropolitan area. ........................................................................................................................143
xiv 

Figure C-5. Mobile measurement route for the Arvada suburbs. ................................................144

Figure C-6. Mobile measurements from 406 to 411 MHz around the Arvada 

spectrum survey site. ....................................................................................................................145

Figure C-7. Mobile measurements from 411 to 416 MHz around the Arvada 

spectrum survey site. ....................................................................................................................146

Figure C-8. Mobile measurements from 416 to 420 MHz around the Arvada 

spectrum survey site. ....................................................................................................................147

Figure C-9.Time slices chosen for processed data from the Denver spectrum 

survey in June 2011. ....................................................................................................................148

Figure C-10. Static spectrum survey measurements from 406 to 411 MHz 

processed over a one-hour time slice. ..........................................................................................150

Figure C-11. Static spectrum survey measurements from 406 to 411 MHz 

processed over a one-day time slice.............................................................................................151

Figure C-12. Static spectrum survey measurements from 406 to 411 MHz 

processed over a one-week time slice. .........................................................................................152

Figure C-13. Static spectrum survey measurements from 406 to 411 MHz 

processed over a two-week time slice. .........................................................................................153

Figure C-14. Static spectrum survey measurements from 406 to 411 MHz 

processed over a one-month time slice. .......................................................................................154

Figure C-15. Static spectrum survey measurements from 411 to 416 MHz 

processed over a one-hour time slice. ..........................................................................................155

Figure C-16. Static spectrum survey measurements from 411 to 416 MHz 

processed over a one-day time slice.............................................................................................156

Figure C-17. Static spectrum survey measurements from 411 to 416 MHz 

processed over a one-week time slice. .........................................................................................157

Figure C-18. Static spectrum survey measurements from 411 to 416 MHz 

processed over a two-week time slice. .........................................................................................158

Figure C-19. Static spectrum survey measurements from 411 to 416 MHz 

processed over a one-month time slice. .......................................................................................159

Figure C-20. Static spectrum survey measurements from 416 to 420 MHz 

processed over a one-hour time slice. ..........................................................................................160

Figure C-21. Static spectrum survey measurements from 416 to 420 MHz 

processed over a one-day time slice.............................................................................................161
xv

Figure C-22. Static spectrum survey measurements from 416 to 420 MHz 

processed over a one-week time slice. .........................................................................................162

Figure C-23. Static spectrum survey measurements from 416 to 420 MHz 

processed over a two-week time slice. .........................................................................................163

Figure C-24. Static spectrum survey measurements from 416 to 420 MHz 

processed over a one-month time slice. .......................................................................................164
xvi 

LIST OF TABLES 

Table 1. Scheduled events for the broad-frequency system. ...........................................................8

Table 2. Generic event parameters for measurement algorithms. .................................................10

Table 3. Threshold levels for measured frequency ranges. ...........................................................12

Table 4. Notes on Figures 3–109. ................................................................................................122
xvii 

ABBREVIATIONS/ACRONYMS

ACF Antenna Correction Factor 

ADS-B Automatic Dependent Surveillance Broadcast 

AFSCN Air Force Satellite Control Network 

ANLE Airport Network and Location Equipment 

ARSR Air-Route Surveillance Radar 

ASR Airport Surveillance Radar 

ATC Air Traffic Control 

ATCRBS Air Traffic Control Radar Beacon System 

ATIS Automated Terminal Information System 

ATSC Advanced Television Systems Committee 

AWOS Automated Weather Observation System 

CDF Cumulative Distribution Function 

CCDF Complementary Cumulative Distribution Function 

CW Continuous Wave 

dB Decibel 

dBi Decibel isotropic 

dBm Decibel milliwatt 

dBμV Decibel micro-volt 

DC Direct Current 

DCP Data Collection Platform 

DGPS Differential Global-Positioning System 

DIA Denver International Airport 

DME Distance Measuring Equipment 

DOI Department of Interior 
xviii 

DSCS Defense Satellite Communications Systems 

DSN Deep Space Network 

DTV Digital Television 

DVA Department of Veterans Affairs 

ELT Emergency Locating Transmitter 

EPIRB Emergency Position-Indicating Radar Beacons 

EPLRS Enhanced Position Location Reporting System 

EVA Extra-Vehicular Activity 

FAA Federal Aviation Administration 

FCC Federal Communications Commission 

FFT Fast-Fourier Transform 

FS-CCDF Field-Strength, Complementary Cumulative Distribution Function 

GHz Gigahertz 

GMF Government Master File 

GOES Geostationary Operational Environmental Satellites 

GPS Global Positioning System 

INMARSAT International Marine/Maritime Satellite 

ISM Industrial, Scientific, and Medical 

ITS Institute for Telecommunication Sciences 

JTIDS Joint Tactical Information Distribution System 

kW Kilowatt 

LMR Land Mobile Radio 

LOS Line-of-sight 

LPTV Low Power Television 

LTE Long Term Evolution 
xix 

MDS Multi-point Distribution Systems 

MHz Megahertz 

MLS Microwave Landing System 

MSL Mean Sea Level 

NASA National Aeronautics and Space Administration 

NATO North Atlantic Treaty Organization 

NEXRAD Next-Generation Radar 

NOAA National Oceanic and Atmospheric Administration 

NSF National Science Foundation 

NTIA National Telecommunication and Information Administration 

NTSC National Television Systems Committee 

OSM Office of Spectrum Management 

PCS Personal Communication System 

PDF Probability Distribution Function 

PGM Precision-Guided Munitions 

RBW Resolution Bandwidth 

RF Radio Frequency 

RFID Radio Frequency Identification 

RNSS Radio Navigation Satellite Service 

RSMS Radio Spectrum Measurement Sciences 

SA Spectrum Analyzer 

SAR Synthetic Aperture Radar 

SARSAT Search and Rescue Satellite Aided Tracking 

SGLS Space-Ground Link System 

TACAN Tactical Air Navigation 
xx

TCAS Traffic Alert and Collision Avoidance System 

TDRSS Tracking and Data Relay Satellite System 

TDwFFT Time-Domain Acquisition with Fast-Fourier Transform Processing 

TDWR Terminal Doppler Weather Radar 

TIROS Television Infrared Operational Satellite

TTC Telemetry, Tracking and Command 

TV Television 

TVWS Television White Space 

U-NII Unlicensed National Information Infrastructure 

UPS Uninterruptible Power Supply 

VBW Video Bandwidth 

VHF Very-High Frequency 

VOR VHF Omnidirectional Range 

WAAS Wide Area Augmentation System 

WAPA Western Area Power Administration 

WGS Wideband Gapfiller Satellite 

WLAN Wireless Local Area Network 

YIG Yttrium Iron Garnet 
BROADBAND SPECTRUM SURVEY IN THE DENVER AND BOULDER, 

COLORADO, METROPOLITAN AREAS 

Chriss Hammerschmidt, Heather E. Ottke1, J. Randy Hoffman2

NTIA is responsible for managing the Federal Government’s use of the radio 

spectrum. In discharging this responsibility, NTIA uses the Radio Spectrum 

Measurement Sciences system to collect spectrum occupancy data for radio 

frequency assessments. This report shows measured frequency data spanning 

spectrum from 108 MHz to 10 GHz in the metropolitan area of Denver, Colorado, 

during the month of June 2011. 

Keywords: land mobile radio (LMR); radar emission spectrum; radio spectrum measurements 

sciences (RSMS); radio frequency environment; spectrum occupancy; spectrum 

resource assessment; spectrum survey 

1 INTRODUCTION 

1.1 Background 

The National Telecommunications and Information Administration (NTIA) is responsible for 

managing the Federal Government’s use of the radio spectrum. Part of this responsibility is to 

establish policies concerning spectrum assignment, allocation, and use; and to provide the 

various departments and agencies with the guidance to ensure that their conduct of 

telecommunications activities is consistent with these policies [1]. In discharging this 

responsibility, NTIA 1) assesses spectrum utilization, 2) identifies existing and/or potential 

compatibility problems among the telecommunication systems that belong to various 

departments and agencies, 3) provides recommendations for resolving any compatibility 

conflicts that may exist in the use of the frequency spectrum, and 4) recommends changes to 

promote spectrum efficiency and improve spectrum management procedures. 

Since 1973, NTIA has been collecting data on radio frequency spectrum utilization. The Radio 

Spectrum Measurement Sciences (RSMS) system was developed by NTIA to perform thorough 

and accurate spectrum occupancy measurements in virtually any location in a broad range of 

spectrum bands. These measurements support agency needs such as Federal spectrum 

management, usage assessments, interference resolution, and propagation research support. The 

RSMS-4 measurement vehicle used to conduct the measurements reported here is the fourth 

generation mobile measurement laboratory developed by NTIA and is equipped with state-ofthe-art instrumentation, measurement methods, and analysis capabilities. 

 

1

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

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

2

 The author was formerly with the Institute for Telecommunication Sciences and is now retired. 
2

1.2 Purpose of this Survey 

Under U.S. Department of Commerce Departmental Organizational Order 25-7 [2], one of the 

assigned functions of the Institute for Telecommunication Sciences (ITS) is to acquire, analyze, 

synthesize, and disseminate data and perform research in general on the description and 

prediction of electromagnetic transmission, noise, and interference, and on methods for 

improving the use of the spectrum for telecommunication purposes. 

RSMS measurement activities are carried out as part of ongoing research projects undertaken to 

fulfill the statutory directive that NTIA conduct research and analysis in the general field of 

telecommunications sciences. They may also be carried out at the direction of the Office of 

Spectrum Management (OSM), either on behalf of another Federal agency that has requested 

assistance from OSM or in support of OSM’s mission to meet the spectrum management 

requirements of NTIA. 

This survey of spectrum occupancy in the Denver and Boulder, Colorado, metropolitan areas 

was conducted in 2011 as part of ongoing research efforts. The spectrum occupancy data 

presented in this report does not include identification of specific emitters. The data are provided 

for the spectrum management community to enable a better understanding of how 

telecommunication systems use the licensed and unlicensed spectrum, and to make available 

information on current frequency band usage. 

These measurements were not intended to assess the feasibility of using alternative services or 

systems in a band. To generalize spectrum occupancy measurements for such analysis, further 

consideration must be given to the spectrum management procedures and types of missions 

performed in each band. 

1.3 Report Layout 

Section 2 begins by describing criteria used to select a spectrum survey measurement site and 

describes the measurement site selected for the Denver, CO Metropolitan Area, spectrum survey. 

The section also gives a brief description of the measurement system along with the 

measurement parameters for this spectrum survey. Section 3 presents the measurement results 

followed by a discussion of frequency bands, the types of signals that exist in the bands and 

notes about the measurement graphs. Appendix A explains the calculations for the graphs shown 

in Section 3. A description of the RSMS-4 system is given in Appendix B. Appendix C shows 

results for mobile measurements performed in the greater metropolitan Denver, CO, area and a 

mobile measurement in the immediate vicinity of this spectrum survey. Finally, a comparison 

between the static measurements of this survey and mobile measurements is given to enable the 

reader to better understand static occupancy measurements taken at one location versus mobile 

occupancy measurements taken across a specific area. 
3

2 MEASUREMENTS IN THE DENVER METROPOLITAN AREA 

2.1 General Site Selection 

The area chosen for a spectrum survey will affect measured spectrum occupancy. For example, 

measurements taken in one metropolitan area, such as Denver, CO, [3] or Los Angeles, CA, [4]

may not represent activity in other metropolitan areas. Some metropolitan areas will lack strong 

emissions from maritime radionavigation sources or extensive military operations. On the other 

hand, cities such as San Diego [5] or San Francisco [6], with major naval installations, will show 

higher levels of usage in bands supporting those operations. Emissions from the following 

sources are commonly observed during a spectrum survey: 

 Land-mobile, marine-mobile, and air-mobile communications radios 

 Terrestrial, marine, and airborne radars, and airborne radio transmitters 

 Radionavigation emitters, such as Tactical Air Navigation (TACAN) and VHF 

Omnidirectional Range (VOR), either from ground or airborne transmitters within the 

range of our measurement system. 

 Cellular, broadband wireless, and trunked communication systems 

 Broadcasting transmitters such as digital television (DTV) and multi-point distribution 

systems (MDS, wireless cable television (TV)) 

 Industrial, scientific, and medical (ISM) sources, including vehicular tracking systems, 

welders, and microwave ovens 

 Unlicensed National Information Infrastructure (U-NII) systems 

 Common carrier (point-to-point) microwave signals 

 Satellite earth station uplink transmissions 

Potential emissions not normally receivable during spectrum surveys may include: 

 Satellite downlink emissions 

 Galactic and solar noise 

 Some types of spread spectrum signals (such as Global Positioning System codes (GPS)) 

 Licensed radio transmitters that are turned off 

 Receive-only systems, passive sensing systems and systems used for radio astronomy 

observations. 
4

Choice of measurement site within an area will also affect measured spectrum occupancy. In an 

area with heavy foliage, rough terrain, or widely dispersed transmitters, multiple measurement 

locations may be required to accurately characterize usage. 

The measurement site must be carefully chosen to intercept a large majority of the signals in the 

area and to minimize logistical problems. To intercept a large majority of signals in the area the 

site should: 

1. Provide line-of-sight (LOS) coverage so that the probability of intercepting weak signals, 

such as mobile units, is maximized 

2. Limit the number of nearby transmitters to minimize intermodulation or saturation 

problems, even if preselection and/or filtering is used 

3. Limit sources of man-made noise such as impulsive noise from automobile ignition 

systems and electrical machinery 

Primary logistical considerations are: 

1. Commercial power to decrease the probability of power interruptions and increase the 

probability of interruption-free measurements 

2. Security for personnel, vehicle, and electronic hardware 

The ideal site is a well-illuminated, fenced, and patrolled area that satisfies all primary siteselection considerations listed above and has reasonable access to lodging for the operating 

personnel. 

Spectrum occupancy fluctuates over time for individual assignments and across bands. For 

example, frequencies assigned to law enforcement may be used intermittently but are needed for 

special events. During a special event, such as an emergency, disaster, Olympic Games [7], or 

Presidential activities, spectrum requirements may change around that event. Regardless of 

usage, such dedicated channels must be available for any safety-of-life functions and are a 

spectrum requirement. 

Spectrum measurements provide data on expected signal levels and probability of occurrences. 

Such information is difficult to obtain from the Federal Communications Commission (FCC) or 

Government Master File (GMF) frequency assignment databases, or from an understanding of 

spectrum management procedures. 

2.2 Denver Metropolitan Area Measurement Site Description 

The selected measurement site reported here is in Arvada, CO. The name of the location is 

Hackberry Hill and it is located about 12 km from the center of the Denver metropolitan area. 

The site is owned by the Exempla Colorado Lutheran Home Health Care Center. Their building 

is situated to the west of the measurement location and is one story high. During the tests, the 
5

antenna masts were raised approximately 10 m (30 ft.) to get an unobstructed view of the 

surrounding area. 

Arvada is a suburb of the Denver metropolitan area. It is located between the foothills of the 

Rocky Mountains and the Great Plains. The measurement location is shown in Figure 1 and the 

latitude and longitude are 39°49′34.53′′ N and 105°04′55.74′′ W. The elevation at this location is 

1600 meters (5249 feet) above mean sea level (MSL). There were no nearby fixed transmitters. 

The closest DTV transmitter is approximately 16.9 kilometers (10.5 miles) from the 

measurement location. 

Figure 1. MapQuest® map and picture showing the Arvada measurement location (blue triangle). 

2.3 Measurement System Description 

The spectrum survey was conducted from June 7, 2011 to June 29, 2011. This ensured that 

recently developed measurement software and all equipment were functioning optimally and that 

any suspect data could be retaken. The measurement software includes a scheduler so that some 

bands could be measured more often than others. For example, LMR activity occurs throughout 

the day but is intermittent and therefore should be measured as often as possible. Television 

bands can show diurnal variations but are on almost all the time and so are scheduled to be 

measured at different times during the day and at night but may be measured less frequently than 

LMR bands. Some radar bands are not very active in the Denver metropolitan area and so are not 

measured often. The measurement schedule was adjusted to obtain a maximal amount of 

measurements in heavily used bands. 

Each band is measured with a hardware configuration and measurement algorithms specifically 

designed to give the most useful information about the particular type(s) of signal expected in a 

frequency sub-band. The measurement hardware and system parameters considered for each 

signal type and frequency band include: antennas, sweep time, measurement bandwidth, detector 

mode, measurement repetitions, preselector filters, and preamplifier paths. Some bands contain 

multiple signal types, which require tailored measurement algorithms to address the specific 

characteristics of the different types of radio emitters and, therefore, some bands may appear 

more than once in the report. 
6

The RSMS-4 measurement software is automated to control instrument operation and data 

capture for each frequency sub-band. The measurements are repeated according to signal 

intercept probability, signal variability, significance of signal-type and how often it changes, the 

need for data in specific bands, and efficiency of system resources. 

Two separate systems are used. The schematics for both systems are shown in Figure 2. The first 

system, the LMR system, measures only LMR narrowband signals below 500 Megahertz (MHz) 

using the following fixed filters: 108–116 MHz, 138–174 MHz, 216–225 MHz, and 406–420 

MHz. A discone antenna with a frequency specification from 25 MHz to 1300 MHz is used with 

the LMR system. These bands are measured consecutively and as often as possible. 

The second system, named the broad-frequency system, measures wideband television and LMR 

signals below 500 MHz and all other signal types from 500 MHz to 10,000 MHz. The broadfrequency system is a more complex system. The preselectors incorporate digitally-tuned, 

yttrium iron garnet (YIG) and fixed filters in the system. There are different amplifiers for each 

selected hardware path. A discone antenna similar to that used in the LMR system is used with 

the broad-frequency system for measurements below 1000 MHz and an omni-directional antenna 

with a frequency specification from 300 MHz to 18,000 MHz is switched into the broadfrequency system for measurements above 1000 MHz. Measurements of fixed point-to-point 

microwave transmitters in their allocated frequency bands use a one meter dish antenna with 

approximately 30 decibels relative to isotropic (dBi) of gain. The broad-frequency system is used 

for these measurements. 

Figure 2. System schematic for the LMR system and the broad-frequency system. 
7

The preselector/preamplifier unit, schematically depicted in Figure 2, serves the purposes of 

extending the dynamic range, improving measurement system sensitivity, and reducing 

measurement system responses to signals outside the measurement band. The variable attenuator 

in the first preselector is used to adjust the upper and lower bounds of the dynamic range of the 

measurement system. More attenuation is used in bands where strong signals may overload the 

measurement system, and less attenuation is used in bands with weaker signals. RF bandpass 

filters also help prevent system overloads by limiting the power from out-of-band emissions. The 

first amplifier is designed to overcome the cable loss and the amplifier in the second preselector 

is designed to overdrive the spectrum analyzer (SA) noise figure. The SA acquires signals and 

transfers information to a computer. The computer software controls instrument configurations, 

executes measurement routines, records the measured data, and provides real-time system logs of 

the measurement start and stop times and any measurement problems that may occur. 

Four tailored algorithms are used for these measurements: 1) a time-domain acquisition with fast 

Fourier transform (FFT) processing algorithm (TDwFFT), 2) swept-spectrum measurement 

algorithm, 3) stepped-spectrum measurement algorithm, and 4) an azimuthal-scanning 

measurement algorithm. Measurements of frequencies below 500 MHz, independent of the 

system, use the time-domain acquisition with FFT processing to minimize the effects of 

impulsive noise. The swept-spectrum measurement algorithm is a general purpose algorithm and 

is used in bands with multiple signal types or where swept measurements are valid for the 

emission type. The stepped-spectrum measurement algorithm is used in bands where radar 

signals exist, and the azimuthal-scanning measurement algorithm was developed to measure 

fixed point-to-point microwave emissions. 

The LMR system measured two scheduled events: a calibration of the system and actual 

measurements. Events will be described below. Measurements were repeated on an ongoing 

basis for the full month. These bands were measured approximately 1500 times. Calibrations 

were performed a minimum of every 12 hours for both the LMR system and the broad-frequency 

system to ensure the systems were operating correctly. Calibrations were accomplished using 

internal noise diodes and a Y-factor technique [3]. 

The broad-frequency system was set up to measure the 42 scheduled events shown in Table 1

Column 1 shows the event number. Column 2 is a brief description of the type of measurement 

and the measurement algorithm used; for example, event 1 was a calibration in the frequency 

bands from 116–138 MHz, 406–420 MHz, and 420–476 MHz and was measured using the 

TDwFFT algorithm. Event 14 was a measurement in the frequency band from 763 to 1000 MHz 

(which contains signals such as cellular uplinks and downlinks, ISM bands and other 

miscellaneous signals) and was measured using the swept-spectrum measurement algorithm. 

These events are called by a scheduler, which schedules each event using the timing parameters 

shown in columns 3 and 4 of Table 1. Column 3 shows how often the scheduler repeated a 

measurement. Column 4 shows the minimum number of hours between measurements and 

Column 5 shows the total number of times the measurement was made during the course of the 

survey. 

For example, measurements of TV bands were repeated ten times during the survey to capture 

possible variations in the signal and to capture emissions during the day and at night. Radar 

bands were measured every 54 hours since radars in this area typically do not move to different 
8

locations and some radar bands are not occupied in this geographical area. This interval also 

ensured that we measured some radars in the evening to observe variations. Measurement events 

under 500 MHz were repeated as often as possible. The following frequency bands, designated 

by the 0 in column 4, were also measured as often as possible: 

 Cellular_Misc3_763–1000 MHz cellular bands 

 Narrowband_1000–2000 MHz 

 Narrowband_2000–2700 MHz 

 Narrowband_2900–4200 MHz 

 Misc_4400–5000 MHz 

 Misc_5000–7000 MHz 

 Misc_7000–8000 MHz 

 Misc_8000–9000 MHz 

 Misc_9000-10000 MHz 

Table 1. Scheduled events for the broad-frequency system. 

Event Description How 

measurement is 

repeated

Minimum 

Hours 

Between

Total Times 

Measured

1 Calibration_116–138_225–406_420–476MHz (TDwFFT) Repeat Ongoing 12 14

2 Measurement_116–138_225–406_420–476MHz (TDwFFT) Repeat Ongoing 0 41

3 Calibration_TV_174–216_476–500MHz (TDwFFT) Repeat 10x 12 10

4 Measurement_TV_174–216_476–500MHz (TDwFFT) Repeat 10x 12 10

5 Calibration_TV_500–608_614–763MHz (Swept) Repeat 10x 12 10

6 Measurement _TV_500–608_614–763MHz (Swept) Repeat 10x 12 10

7 Calibration_TVWS_180–210MHz (TDwFFT) Repeat 10x 12 10

8 Measurement _TVWS_180–210MHz (TDwFFT) Repeat 10x 12 10

9 Calibration_TVWS_500–608_614–763MHz (Swept) Repeat 10x 12 10

10 Measurement_TVWS_500–608_614–763MHz (Swept) Repeat 10x 12 10

11 Calibration_Radar_420–450MHz (Stepped) Repeat Ongoing 54 7

12 Measurement_Radar_420–450MHz (Stepped) Repeat Ongoing 54 7

13 Calibration_Cellular_Misc_763–1000MHz (Swept) Repeat Ongoing 12 14

14 Measurement_Cellular_Misc_763–1000MHz (Swept) Repeat Ongoing 0 38

15 Calibration_Radar_854–928MHzMHz (Stepped) Repeat Ongoing 54 7

16 Measurement_Radar_854–928MHzMHz (Stepped) Repeat Ongoing 54 7

17 Calibration_Narrowband_1000–2000MHz (Swept) Repeat Ongoing 12 14

18 Measurement_Narrowband_1000–2000MHz (Swept) Repeat Ongoing 0 40

19 Calibration_Radar_1215–1390MHz (Stepped) Repeat Ongoing 54 7

 

3

 Misc refers to other miscellaneous signals that may be present in this frequency band. 
9

20 Measurement_Radar_1215–1390MHz ( Stepped) Repeat Ongoing 54 7

21 Calibration_Narrow_2000–2700MHz (Swept) Repeat Ongoing 12 7

22 Measurement_Narrow_2000–2700MHz (Swept) Repeat Ongoing 0 14

23 Calibration_Radar_2700–2900MHz (Stepped) Repeat Ongoing 54 40

24 Measurement_Radar_2700–2900MHz (Stepped) Repeat Ongoing 54 7

25 Calibration_Radar_2900–3650MHz (Stepped) Repeat Ongoing 54 7

26 Measurement_Radar_2900–3650MHz (Stepped) Repeat Ongoing 54 7

27 Calibration_Narrowband_2900–4200MHz (Swept) Repeat Ongoing 12 7

28 Measurement_Narrowband_2900–4200MHz (Swept) Repeat Ongoing 0 14

29 Calibration_Radar_5250–5925MHz (Stepped) Repeat Ongoing 54 40

30 Measurement_Radar_5250–5925MHz (Stepped) Repeat Ongoing 54 7

31 Calibration_Misc_4400–5000MHz (Swept) Repeat Ongoing 12 7

32 Measurement_Misc_4400–5000MHz (Swept) Repeat Ongoing 0 38

33 Calibration_Misc_5000–7000MHz (Swept) Repeat Ongoing 12 14

34 Measurement_Misc_5000–7000MHz (Swept) Repeat Ongoing 0 38

35 Calibration_Misc_7000–8000MHz (Swept) Repeat Ongoing 12 14

36 Measurement_Misc_7000–8000MHz (Swept) Repeat Ongoing 0 38

37 Calibration_Misc_8000–9000MHz (Swept) Repeat Ongoing 12 14

38 Measurement_Misc_8000–9000MHz (Swept) Repeat Ongoing 0 38

39 Calibration_Misc_9000–10000MHz (Swept) Repeat Ongoing 12 14

40 Measurement_Misc_9000–10000MHz (Swept) Repeat Ongoing 0 38

41 Calibration_Radar_8500–10000MHz (Stepped) Repeat Ongoing 54 7

42 Measurement_Radar_8500–10000MHz (Stepped) Repeat Ongoing 54 7

Each scheduled event is described by a unique set of parameters that include the instrument 

setup, measurement events, and data collection subroutines. Each event also contains 

measurement parameters such as start and stop frequency, sweep time, the number of points per 

trace, the resolution bandwidth (RBW), the video bandwidth (VBW), detector type, filter type, 

and preselector attenuation. Table 2 shows generic parameters for scheduled events for the 

different measurement algorithms discussed above. 

The swept, stepped, and azimuthal-scanning algorithms have similar parameters because they 

use the spectrum mode of the spectrum analyzer. The time-domain parameters are different 

because they use the basic mode of the spectrum analyzer.
10

Table 2. Generic event parameters for measurement algorithms. 

Parameter Sweptspectrum

SteppedspectrumAzimuthalscanningTime-domain 

parameter

FFT 

processing

RBW (MHz) 0.3 1.0 1.0 RBW (kHz) 6.25

VBW (MHz) 0.3 1.0 1.0 Span (kHz) 4.1

Start Frequency (MHz) 4400 2900 4000 1st Channel (MHz) 108

Stop Frequency (MHz) 5000 3650 5000 kHz/Channel (kHz) 6.25

Sweep Time (ms) 1000 12000 1000 Channels/Band 640

Points/Trace 2001 8192 1001 Points/RBW 10

Preselector Antenna 

Ports 2-1 2-1 2-1 Traces/Median 5

Detector Type Average Positive Peak Average Event Acquisition 

Time (min) 1.1

Filter Type Fixed Fixed or 

Tunable

Fixed or 

Tunable Time/median (sec) 0.9

Preselector Attenuation 

(dB) 0 Auto None Window type Flattop

Sweeps/Event 100 751 Preselector Attenuation 

(dB) 30

Step size (MHz) 1

Preselector Antenna 

Ports 2-1

Scan Mode Stepped Filter Center 

Frequency (MHz) 110

Angular Resolution 

(degrees) 1

Azimuth Start

(degrees) 180

Azimuth Stop

(degrees) -180

Median Threshold (dB) 2

Elevation (degrees) 0

After the survey data has been taken, additional processing is necessary to obtain statistical 

descriptions of the data. These processing steps are briefly described in the following section. 
11

3 MEASURED DATA 

There are over 220 individual processed events. Where possible, we have combined events to 

minimize the report graphs while providing useful clarity. The graphs are generated from the 

measurement data using a MATLAB® script developed at ITS. This script has limitations, such 

as layout restrictions that may result in label truncation or displacement. The script also has 

advantages, such as being able to pull information from the FCC and GMF databases to show 

assignments directly in the report graph. 

The frequency allocations, shown in the yellow strips at the top of each figure, are taken from the 

United States Frequency Allocation Chart [8] in which the names of primary services are printed 

in capital letters and secondary services are printed in upper and lower case. The numbers shown 

above the allocation bar are the band-edge frequencies for the allocations. Some of the frequency 

allocation information is truncated in the boxes above the graphs due to the band edge labels. 

There are three presentations of data in this report. Swept-spectrum and TDwFFT data are shown 

using three graphs; stepped-spectrum measurements are shown using two graphs; and azimuthalscanning plots are shown on one plot. 

When three graphs are shown on a page, the top graph is the statistical description of the data at 

each frequency: the maximum value (blue trace), the mean value (black trace), the median value 

(green trace), the minimum value (red trace), and the mean system noise (magenta trace). These 

are referred to in this report as the M4 statistics plots. These were introduced in [3], [4], [5], and 

[6] as Swept/m3 or Swept/m4 measurements. The middle graph shows field strength as a 

function of frequency and time and is commonly referred to as a waterfall plot. These are 

displayed as contour plots having 20 contoured field-strength levels. Red values indicate relative 

maximum field strength levels, and blue values indicate relative minimum field strength levels. 

The bottom graph shows the complementary cumulative distribution functions of the electric 

field strength (FS-CCDFs) as a function of frequency. The probability that a measured signal 

exceeds the specified field-strength is shown in the legend. 

The threshold level, shown by the dashed black trace in the bottom plot, is used to display the 

data in the middle plot (field strength as a function of time and frequency). Threshold levels are 

either set to minimize the display of impulsive noise without excluding low-level signals, such as 

in frequencies below 500 MHz or set to a field-strength level that is likely to be exceeded by the 

system noise less than 0.01% of the time. The thresholds set for various bands are summarized in 

Table 3 and are restated above the FS-CCDF plots. Typically FS-CCDFs can be used to 

understand signal types and are useful for displaying the probability that a signal exceeds a 

certain field-strength level. The spacing of the lines gives us an indication as to whether a signal 

is Gaussian-distributed, pulsed continuous-wave (CW), or another signal type and also is 

indicative of the measurement algorithm used. 
12

Table 3. Threshold levels for measured frequency ranges. 

Frequency Range

(MHz)

Threshold Level

(dB)

108 – 174 10

174 – 216 8

216 – 261 10

261 – 500 8

500 – 4200 6

4400 – 7000 1

7000 – 10000 1.5

Radar or stepped measurements are shown using two graphs. The top graph shows the M4 

statistics and peak system noise statistics, and the bottom graph shows the individual traces so 

that changes in the radar characteristics, such as frequency tuning, can be differentiated. 

Fixed point-to-point microwave measurements taken with the azimuthal-scanning algorithm 

show only one plot in which the frequency is plotted on the x-axis and the azimuthal angle is 

plotted on the y-axis. Relative power is displayed by contour levels. This graph is used to show 

the angular dependence of these transmissions. 

Data presented in these graphs is affected by both the measurement parameters given in Table 2

and the post-processing algorithms. Each graph is plotted with a unique field strength scale to 

show more detail in the plots. Field strength is referenced to the antenna input and calculated so 

that measurements from different systems can be compared. The notation “Referenced to 

antenna input – adjusted for attenuation” in each graph means that any losses due to the antenna 

or cables and attenuators between the preselector and the input of the antenna are accounted for. 

The azimuthal-scanning measurements were taken in the vertical polarization only due to time 

constraints. These plots may show signals received by the antenna side-lobes, readily identified 

as data seen across all azimuthal angles at one frequency. 

The data presentation in each graph is intended to best describe the signal environment within its 

measured frequency band or bands. The measurement range of the receiving system is dependent 

on the system sensitivity in each band. Based on the measurement parameters, algorithms, and 

statistical analysis, we believe that these data represent a good statistical sampling of the activity 

in the radio spectrum in the Denver metropolitan area. Maximum and minimum activity levels 

measured in the spectrum are representations of actual activity levels. The mean and median 

levels provide an unbiased, quantitative estimate of typical received field-strength levels as a 

function of frequency. While the data presented here can be used to infer the spectrum 

occupancy, it cannot be used to infer the statistical percentage of time that channels are occupied. 

Two reasons for this are: 1) the RBW is not always set equal to the channel bandwidth, and 2) 

some events are measured only intermittently, therefore a complete set of statistics is not 

available. To obtain data for the latter purpose, a dedicated time-occupancy study similar to the 

previously reported LMR occupancy study [7], [9] should be performed. 
13

The following figures show results from the spectrum survey. Discussions about each figure 

follow the data in Section 3.1. Only the allocation information necessary to understanding the 

signals represented in the figure being discussed is given in the notes column of Table 4. This 

allocation information is taken from the FCC Online Table of Frequency Allocations [10] and 

the Federal Spectrum Use Summary [11]. For a complete description of the allocations, the 

reader is referred to [1], [8], [10], or [11]. 
14

Figure 3. NTIA spectrum survey results from 108 to 112 MHz in Denver, CO, 2011. 
15

Figure 4. NTIA spectrum survey results from 112 to 116 MHz in Denver, CO, 2011. 
16

Figure 5. NTIA spectrum survey results from 116 to 120 MHz in Denver, CO, 2011. 
17

Figure 6. NTIA spectrum survey results from 120 to 124 MHz in Denver, CO, 2011. 
18

Figure 7. NTIA spectrum survey results from 124 to 132 MHz in Denver, CO, 2011. 
19

Figure 8. NTIA spectrum survey results from 132 to 136 MHz in Denver, CO, 2011. 
20

Figure 9. NTIA spectrum survey results from 136 to 138 MHz in Denver, CO, 2011. 
21

Figure 10. NTIA spectrum survey results from 138 to 143 MHz in Denver, CO, 2011. 
22

Figure 11. NTIA spectrum survey results from 143 to 149 MHz in Denver, CO, 2011. 
23

Figure 12. NTIA spectrum survey results from 149 to 154 MHz in Denver, CO, 2011. 
24

Figure 13. NTIA spectrum survey results from 154 to 159 MHz in Denver, CO, 2011. 
25

Figure 14. NTIA spectrum survey results from 159 to 164 MHz in Denver, CO, 2011. 
26

Figure 15. NTIA spectrum survey results from 164 to 169 MHz in Denver, CO, 2011. 
27

Figure 16. NTIA spectrum survey results from 169 to 174 MHz in Denver, CO, 2011. 
28

Figure 17. NTIA spectrum survey results from 174 to 192 MHz in Denver, CO, 2011. 
29

Figure 18. NTIA spectrum survey results from 192 to 216 MHz in Denver, CO, 2011. 
30

Figure 19. NTIA spectrum survey results from 216 to 221 MHz in Denver, CO, 2011. 
31

Figure 20. NTIA spectrum survey results from 221 to 225 MHz in Denver, CO, 2011. 
32

Figure 21. NTIA spectrum survey results from 225 to 237 MHz in Denver, CO, 2011. 
33

Figure 22. NTIA spectrum survey results from 237 to 243 MHz in Denver, CO, 2011. 
34

Figure 23. NTIA spectrum survey results from 243 to 249 MHz in Denver, CO, 2011. 
35

Figure 24. NTIA spectrum survey results from 249 to 261 MHz in Denver, CO, 2011. 
36

Figure 25. NTIA spectrum survey results from 261 to 273 MHz in Denver, CO, 2011. 
37

Figure 26. NTIA spectrum survey results from 273 to 279 MHz in Denver, CO, 2011. 
38

Figure 27. NTIA spectrum survey results from 279 to 285 MHz in Denver, CO, 2011. 
39

Figure 28. NTIA spectrum survey results from 285 to 291 MHz in Denver, CO, 2011. 
40

Figure 29. NTIA spectrum survey results from 291 to 297 MHz in Denver, CO, 2011. 
41

Figure 30. NTIA spectrum survey results from 297 to 303 MHz in Denver, CO, 2011. 
42

Figure 31.NTIA spectrum survey results from 303 to 309 MHz in Denver, CO, 2011. 
43

Figure 32. NTIA spectrum survey results from 309 to 315 MHz in Denver, CO, 2011. 
44

Figure 33. NTIA spectrum survey results from 315 to 321 MHz in Denver, CO, 2011. 
45

Figure 34. NTIA spectrum survey results from 321 to 345 MHz in Denver, CO, 2011. 
46

Figure 35. NTIA spectrum survey results from 345 to 351 MHz in Denver, CO, 2011. 
47

Figure 36. NTIA spectrum survey results from 351 to 357 MHz in Denver, CO, 2011. 
48

Figure 37. NTIA spectrum survey results from 357 to 363 MHz in Denver, CO, 2011. 
49

Figure 38. NTIA spectrum survey results from 363 to 369 MHz in Denver, CO, 2011. 
50

Figure 39. NTIA spectrum survey results from 369 to 393 MHz in Denver, CO, 2011. 
51

Figure 40. NTIA spectrum survey results from 393 to 406 MHz in Denver, CO, 2011. 
52

Figure 41. NTIA spectrum survey results from 406 to 411 MHz in Denver, CO, 2011. 
53

Figure 42. NTIA spectrum survey results from 411 to 416 MHz in Denver, CO, 2011. 
54

Figure 43. NTIA spectrum survey results from 416 to 420 MHz in Denver, CO, 2011. 
55

Figure 44. NTIA spectrum survey results from 420 to 444 MHz in Denver, CO, 2011. 
56

Figure 45. NTIA spectrum survey results from 420 to 450 MHz in Denver, CO, 2011. This measurement was taken using the steppedspectrum measurement algorithm. 
57

Figure 46. NTIA spectrum survey results from 444 to 468 MHz in Denver, CO, 2011. 
58

Figure 47. NTIA spectrum survey results from 468 to 476 MHz in Denver, CO, 2011. 
59

Figure 48. NTIA spectrum survey results from 476 to 500 MHz in Denver, CO, 2011. 
60

Figure 49. NTIA spectrum survey results from 500 to 524 MHz in Denver, CO, 2011. 
61

Figure 50. NTIA spectrum survey results from 524 to 548 MHz in Denver, CO, 2011. 
62

Figure 51. NTIA spectrum survey results from 548 to 572 MHz in Denver, CO, 2011. 
63

Figure 52. NTIA spectrum survey results from 572 to 596 MHz in Denver, CO, 2011. 
64

Figure 53. NTIA spectrum survey results from 596 to 620 MHz in Denver, CO, 2011. 
65

Figure 54. NTIA spectrum survey results from 620 to 644 MHz in Denver, CO, 2011. 
66

Figure 55. NTIA spectrum survey results from 644 to 668 MHz in Denver, CO, 2011. 
67

Figure 56. NTIA spectrum survey results from 668 to 692 MHz in Denver, CO, 2011. 
68

Figure 57. NTIA spectrum survey results from 692 to 716 MHz in Denver, CO, 2011. 
69

Figure 58. NTIA spectrum survey results from 716 to 740 MHz in Denver, CO, 2011. 
70

Figure 59. NTIA spectrum survey results from 740 to 763 MHz in Denver, CO, 2011. 
71

Figure 60. NTIA spectrum survey results from 763 to 800 MHz in Denver, CO, 2011. 
72

Figure 61. NTIA spectrum survey results from 800 to 833 MHz in Denver, CO, 2011. 
73

Figure 62. NTIA spectrum survey results from 833 to 869 MHz in Denver, CO, 2011. 
74

Figure 63. NTIA spectrum survey results from 869 to 902 MHz in Denver, CO, 2011. 
75

Figure 64. NTIA spectrum survey results from 902 to 935 MHz in Denver, CO, 2011. 
76

Figure 65. NTIA spectrum survey results from 902 to 928 MHz in Denver, CO, 2011. This measurement was taken using the steppedspectrum measurement algorithm. 
77

Figure 66. NTIA spectrum survey results from 935 to 962 MHz in Denver, CO, 2011. 
78

Figure 67. NTIA spectrum survey results from 971 to 1000 MHz in Denver, CO, 2011. 
79

Figure 68. NTIA spectrum survey results from 1000 to 1150 MHz in Denver, CO, 2011. 
80

Figure 69. NTIA spectrum survey results from 1150 to 1300 MHz in Denver, CO, 2011. 
81

Figure 70. NTIA spectrum survey results from 1300 to 1400 MHz in Denver, CO, 2011. 
82

Figure 71. NTIA spectrum survey results from 1215 to 1390 MHz in Denver, CO, 2011. This measurement was taken using the 

stepped-spectrum measurement algorithm. 
83

Figure 72. NTIA spectrum survey results from 1400 to 1450 MHz in Denver, CO, 2011. 
84

Figure 73. NTIA spectrum survey results from 1450 to 1600 MHz in Denver, CO, 2011. 
85

Figure 74. NTIA spectrum survey results from 1600 to 1750 MHz in Denver, CO, 2011. 
86

Figure 75. NTIA spectrum survey results from 1750 to 1900 MHz in Denver, CO, 2011. 
87

Figure 76. NTIA spectrum survey results from 1900 to 2000 MHz in Denver, CO, 2011. 
88

Figure 77. NTIA spectrum survey results from 2000 to 2100 MHz in Denver, CO, 2011. 
89

Figure 78. NTIA spectrum survey results from 2100 to 2250 MHz in Denver, CO, 2011. 
90

Figure 79. NTIA spectrum survey results from 2250 to 2400 MHz in Denver, CO, 2011. 
91

Figure 80. NTIA spectrum survey results from 2400 to 2550 MHz in Denver, CO, 2011. 
92

Figure 81. NTIA spectrum survey results from 2550 to 2700 MHz in Denver, CO, 2011. 
93

Figure 82. NTIA spectrum survey results from 2700 to 2900 MHz in Denver, CO, 2011. This measurement was taken using the 

stepped-spectrum measurement algorithm. 
94

Figure 83. NTIA spectrum survey results from 2900 to 3050 MHz in Denver, CO, 2011. 
95

Figure 84. NTIA spectrum survey results from 3050 to 3150 MHz in Denver, CO, 2011. 
96

Figure 85. NTIA spectrum survey results from 3150 to 3300 MHz in Denver, CO, 2011. 
97

Figure 86. NTIA spectrum survey results from 3300 to 3450 MHz in Denver, CO, 2011. 
98

Figure 87. NTIA spectrum survey results from 3450 to 3550 MHz in Denver, CO, 2011. 
99

Figure 88. NTIA spectrum survey results from 3550 to 3700 MHz in Denver, CO, 2011. 
100

Figure 89. NTIA spectrum survey results from 3700 to 3850 MHz in Denver, CO, 2011. 
101

Figure 90. NTIA spectrum survey results from 3850 to 4000 MHz in Denver, CO, 2011. 
102

Figure 91. NTIA spectrum survey results from 4000 to 4200 MHz in Denver, CO, 2011. 
103

Figure 92. NTIA spectrum survey results from 2900 to 3650 MHz in Denver, CO, 2011. This measurement was taken using the 

stepped-spectrum measurement algorithm. 
104

Figure 93. NTIA spectrum survey results from 4000 to 5000 MHz in Denver, CO, 2011. This measurement was taken using the 

azimuth-scanning measurement algorithm. 
105

Figure 94. Compass centered on Arvada measurement location. The compass shows true north. Zero degrees on the plot is magnetic 

north. Proximity of Rocky Mountain Metropolitan Airport, DIA, and Buckley Air Force Base are shown. 
106

Figure 95. This graph is a close-up view of Figure 92, showing radio altimeter signatures. 
107

Figure 96. NTIA spectrum survey results from 4400 to 5000 MHz in Denver, CO, 2011. This measurement was taken using the sweptspectrum measurement algorithm. 
108

Figure 97. NTIA spectrum survey results from 5000 to 5600 MHz in Denver, CO, 2011. This measurement was taken using the sweptspectrum measurement algorithm. 
109

Figure 98. NTIA spectrum survey results from 5600 to 6200 MHz in Denver, CO, 2011. This measurement was taken using the sweptspectrum measurement algorithm. 
110

Figure 99. NTIA spectrum survey results from 6200 to 7000 MHz in Denver, CO, 2011. This measurement was taken using the sweptspectrum measurement algorithm. 
111

Figure 100. NTIA spectrum survey results from 5250 to 5925 MHz in Denver, CO, 2011. This measurement was taken using the 

stepped-spectrum measurement algorithm. 
112

Figure 101. NTIA spectrum survey results from 5925 to 7000 MHz in Denver, CO, 2011. This measurement was taken using the 

azimuth-scanning measurement algorithm. 
113

Figure 102. NTIA spectrum survey results from 7000 to 7500 MHz in Denver, CO, 2011. This measurement was taken using the 

swept-spectrum measurement algorithm. 
114

Figure 103. NTIA spectrum survey results from 7000 to 7500 MHz in Denver, CO, 2011. This measurement was taken using the 

azimuth-scanning measurement algorithm. 
115

Figure 104. NTIA spectrum survey results from 7500 to 8000 MHz in Denver, CO, 2011. This measurement was taken using the 

swept-spectrum measurement algorithm. 
116

Figure 105. NTIA spectrum survey results from 7500 to 8000 MHz in Denver, CO, 2011. This measurement was taken using the 

azimuth-scanning measurement algorithm. 
117

Figure 106. NTIA spectrum survey results from 8000 to 9000 MHz in Denver, CO, 2011. This measurement was taken using the 

swept-spectrum measurement algorithm. 
118

Figure 107. NTIA spectrum survey results from 8000 to 9000 MHz in Denver, CO, 2011. This measurement was taken using the 

azimuth-scanning measurement algorithm. 
119

Figure 108. NTIA spectrum survey results from 9000 to 10000 MHz in Denver, CO, 2011. This measurement was taken using the 

swept-spectrum measurement algorithm. 
120

Figure 109. NTIA spectrum survey results from 8500 to 10000 MHz in Denver, CO, 2011. This measurement was taken using the 

stepped-spectrum measurement algorithm. 
121

3.1 Discussion of Measured Data 

A discussion of Figures 3–6 is provided to give the reader an understanding of how to interpret 

the data contained in the graphs. After this brief introduction, Table 4 provides notes about 

specific measurement results presented in the figures. For a more complete understanding of the 

frequency allocations in each measured band, the reader is directed to references [1], [8], [10], 

and [11]. 

Figure 3 shows a signal from 108.0 to 108.1 MHz that exceeds a field-strength level of 

approximately 37 dBμV/m with a probability of 96.18%. We also see that the signal has a 0.09% 

probability of exceeding approximately 57 dBμV/m. The waterfall plot shows this signal is on 

continuously. The waterfall plot also shows the presence of impulsive noise as evidenced by the 

horizontal striping in the data. Time data is plotted every 16.45 minutes for a total time of 

approximately 30,000 minutes, 500 hours, or 21 days. There is another signal at approximately 

111.7 MHz that exceeds a field-strength level of approximately 20 dBμV/m with a probability of 

96.18% and the field-strength level of 33 dBμV/m with a probability of 0.09%. This signal was 

on intermittently for the entire time that data was taken. This particular signal corresponds to an 

assignment in the GMF database. Most of the activity in this band is suppressed due to the 30 dB 

of preselector attenuation that had to be added to overcome adjacent channel noise sources. An 

attenuator applied in the entire measurement band reduces sensitivity to low-power signals; 

therefore, future surveys may include a high-pass filter or attenuation to minimize out-of-band 

signals that leak into the band of interest. The mean system noise level is at approximately 22 

dBμV/m and the threshold used to plot the time-information is 10 dB above the mean system 

noise level. 

Figure 4 shows data from 112 to 116 MHz. There is a prominent signal at about 115.4 MHz that 

was on continuously during the survey. It exceeds a field-strength level of approximately 38

dBμV/m with a probability of 88.40%. There is another low-level signal at approximately 114.6 

MHz that was on during the entire survey, as noted by its presence at the 96.18% level, but 

shows up in the waterfall plot only intermittently because it does not break above the threshold. 

We notice in regions where there is no signal, the FS-CCDF lines are spaced in field strength by 

approximately 1 dB which indicates the system noise is Gaussian distributed and was measured 

with the TDwFFT algorithm. The upper lines are more widely spaced due to the presence of 

impulsive noise. The mean system noise trace lies slightly below the mean and median data 

traces, which indicates that external noise sources such as impulsive noise or broadband 

emissions have contributed to the noise floor of the measurement system. 

Figure 5 shows data taken from 116 MHz to 120 MHz. There are signals that exceed the 96.18% 

field strength level at 116.3 MHz, 117.9 MHz, 117.97 MHz, and several signals between 118.5 

and 120 MHz. There is also a lot of impulsive noise in this band which exceeds a given fieldstrength level with a small probability. Some signals are on continuously and others appear 

intermittently. 

Figure 6 shows data taken from 120 MHz to 124 MHz. There is a signal at approximately 121.25 

MHz that exceeds a field-strength level of -5 dBμV/m with a probability of 67.72%. This is a 
122

low-power signal that appears infrequently in the middle of the graph because it exceeds the 

threshold level only 2.02% of the time. 

Table 4. Notes on Figures 3–109. 

Figure(s)

Frequency 

Range (MHz) Notes

3-5 108.0–117.975 The aeronautical radionavigation signals in this band, which include aviation, 

VOR, and Differential Global-Positioning System (DGPS), are generally lowlevel signals. This band is adjacent to the 88–108 MHz FM radio band which, 

in the Denver area, has a high-level signal at 107.9 MHz. To suppress the FM 

signal above 108 MHz, we inserted 30 dB of preselector attenuation into the 

108–116 MHz frequency bands, which reduces the ability of our system to 

detect the low-level aeronautical radionavigation signals. Consequently, 

measurement results may understate Denver area usage in frequencies from 108 

to 116 MHz .

5-8 117.975–136.0 The aeronautical mobile signals in this band originate from air traffic control 

(ATC), private aircraft, and search and rescue. These signals are characterized 

by their small bandwidth and are typically only detected for short periods, as 

can be seen in Figures 5–8.

9 136.0–137.0

137.0–138.0

The signals in these bands originate from aeronautical mobile, space operations 

and research (space-to-earth) transmissions. The FAA uses this band for ATC 

via the Automated Weather Observation System (AWOS) and the Automated 

Terminal Information System (ATIS). The National Aeronautics and Space 

Administration (NASA) uses this band for tracking and telemetry and the 

National Oceanic and Atmospheric Administration (NOAA) uses the band to 

collect meteorological data from the Geosynchronous Operational Environment 

Satellite (GOES). The Denver area survey shows low-level transmissions in 

this band.

10, 11 138.0–144.0 This band is generally used for non-tactical, trunked military land mobile 

communications and civil air patrol. We see several signals between 138.0 and 

139.5 MHz and between 143.0 and 144.0 MHz. There is a single strong signal 

at approximately 141.4 MHz but with a received field strength of only around 

40 dBμV/m.

11 144.0–148.0 The signals in this band are from amateur radio and amateur satellite. There are 

no Federal uses between 144.0–146.0 MHz. Most of the signals in this figure 

show moderate field strengths; however, they are typically on for very short 

periods of time.

11-14 148.0–162.0 These frequency bands are used by NASA for satellite uplinks and 

infrastructure functions. Other fixed or mobile signals for Civil Air Patrol, 

military non-tactical mobile, fixed communications, transit-satellite downlinks, 

land transportation, public safety, industrial, Earth telecommand, VHF distress 

systems communication, and industrial are found in this band. Maritime-mobile 

signals would be found at 156.2475–157.1875 MHz and 161.575–162.0125 

MHz, but are not seen in the Denver area.

14-16 162.0–174.0 Fixed and mobile transmitters such as LMR and weather radio, used by public 

safety and industry, are found throughout this band. The signal at 162.55 MHz 

is a public broadcast weather information channel. The signal activity around 

164.5 MHz could be a modulated signal, an emission that frequency hops, or 

multiple signals turning on and off.
123

Figure(s)

Frequency 

Range (MHz) Notes

17, 18 174.0–216.0 This part of the spectrum is used for broadcasting television. Channels 7, 9, 11, 

and 13 are occupied with Advanced Television Systems Committee (ATSC)

transmissions. There are signals in the white spaces between these channels 

which could be from subscription TV services or limited wireless microphones.

There are no Federal uses in this band.

19 216.0–220.0 The signals in this band are from fixed, mobile, radiolocation and amateur 

transmitters. The users in this band are automated maritime 

telecommunications systems, radiolocation, and non-Government telemetry, 

tracking and command (TTC). There are several experimental research 

allocations in this range. There is little activity in this band from approximately 

216.5–218 MHz and again from 218.6–219.7 MHz. The signal at 

approximately 218.6 MHz appeared during the 3rd day and remained present 

through the end of the spectrum survey.

19, 20 220.0–225.0 Fixed and land mobile signals are found from 220.0 to 222.0 MHz and amateur

signals from 222.0 to 225.0 MHz. The general uses in these bands are trunked 

and conventional LMR systems and amateur (1.25m band) radio. The four 

signals observed from 224.5 to 225.0 MHz have an impact on the mean curve.

21-34 225.0–328.6 This band is used for military tactical and training communications including 

ATC, space operations from 267 to 273 MHz, space-to-earth and earth-to-space 

communications, and mobile-satellite from 312 to 315 MHz. The National 

Science Foundation (NSF) uses this band for radio astronomy research from 

322 to 328.6 MHz. There are no FCC assignments in these bands. These figures 

show low usage.

34 328.6–335.4 The only allocated signals in this band are for aeronautical radionavigation 

transmissions. Instrument landing systems are used by the Federal Aviation 

Administration (FAA) and DGPS and microwave scanning beam landing 

systems are used by NASA. Some of these assignments are paired with 

frequencies from 108 to 117 MHz and frequencies from 960 to 1215 MHz for 

VORs and TACANs. We see both intermittent signals and signals that are on 

continuously. We do not see a lot of spectrum use in this band. 

34-40 335.4–399.9 This band is used by the military, North American Treaty Organization 

(NATO), U.S. Coast Guard, FAA and NASA for radio and airborne 

communications; the military uses frequencies from 380 to 399.9 MHz for 

trunked LMR. We see both intermittent signals and signals that are on 

continuously. We do not see a lot of spectrum use in this frequency band.

40 399.9–400.05

400.05–400.15

400.15–406.0

In this figure, it is not possible to read the primary allocation for two narrow 

bandwidths, 399.9–400.05 MHz and 400.05–400.15 MHz. The allocation for 

399.9–400.05 MHz is “RADIONAVIGATION-SATELLITE, MOBILESATELLITE.” We saw a continuous 400 MHz signal in Denver.

The allocation for 400.05–400.15 MHz is the “STANDARD FREQUENCY 

AND TIME SIGNAL-SATELLITE” at 400.1 MHz ± 25 kHz. We saw one 

low-level signal in this band.

Meteorological aids occupy the band 400.15–406.0 MHz and include NOAA 

and Department of Interior (DOI) radiosonde systems and satellite transmitter 

uplinks called data collection platforms (DCP). The military also uses this band 

for radio communication and MedRadio. We saw a number of signals that were 

on intermittently.
124

Figure(s)

Frequency 

Range (MHz) Notes

41-43 406–406.1

406.1–420.0

The primary allocation in the 406–406.1 band is “MOBILE-SATELLITE,” 

which cannot be read from the graph. This band is used by Emergency 

Position-Indicating Radio Beacon (EPIRB), the Emergency Locator 

Transmitter (ELT) systems and for distress alert and locations using Search and 

Rescue Satellite Aided Tracking (SARSAT) to public safety rescue authorities. 

We did not see any signals in this band in this survey.

The signals in the 406.1–420.0 band are from fixed, land-mobile, radio 

astronomy, and space research signals. Federal agencies use these bands for 

trunked LMR and transmission of hydrologic and meteorological data. The 

NSF uses this for radio astronomy and NASA used this for remote operation of 

cranes and extra-vehicular activity (EVA) communications. There are LMR 

control channels from 406.1 to 411 MHz. There appears to be some type of 

impulsive noise source generated from approximately 419.25 to 420 MHz as 

shown by the horizontal “scratch marks” in the waterfall plot and from the 

raised maximum trace in the top graph.

44-46 420.0–450.0 The signals in this band originate from radiolocation and amateur radio. 

General uses in this band include private land mobile and amateur radio. 

Certain military and Federal agencies also use this band for long-range 

surveillance radars, enhanced position location reporting systems (EPLRS), 

space telecommand (449–451 MHz), wind-profiler weather radars (449 MHz), 

and synthetic aperture radars (SARs) (432-438 MHz). This frequency range 

was measured using a stepped-spectrum measurement algorithm (Figure 45) to 

detect radar signals and a swept-spectrum measurement algorithm (Figures 44

and 46) to detect all other signals. The signal at approximately 434 MHz in 

Figure 44 is also seen in Figure 45.

46, 47 450.0–470.0 Most of the signals in this band originate from land-mobile and fixed

communications by non-Federal users. The secondary allocation from 460 to 

470 MHz is for Federal meteorological satellite users. General uses in these 

bands are remote pickup, low power auxiliary, private land mobile, and 

maritime. Federal agencies use this for LMR shared systems and mutual aid 

responses with public safety agencies, and testing and evaluation of programs. 

There are medical telemetry transmissions occupying this band and NASA uses 

some of these frequencies to support balloon experiments. There are also spaceto-earth and personal radio communications. This part of the spectrum is 

heavily used as indicated by the number of signals that have 96.18% 

exceedance levels in the FS-CCDF plot in Figure 46.

47-49 470.0–512.0 These bands are used by fixed, land-mobile and broadcasting services.

However, there is no land-mobile activity in the Denver area in this band. Uses 

in this band include public mobile, broadcast radio (Channels 14–19), low 

power television (LPTV), TV translator/booster, low power auxiliary, private

and land mobile services. Federal agencies use this band for shared LMR 

systems and mutual aid responses with the public sector. During the 

measurement, Channel 16 (482.0 to 488.0 MHz) was originally on and then 

turned off.
125

Figure(s)

Frequency 

Range (MHz) Notes

49-60 512.0–793.0 Broadcasting, land-mobile, radio astronomy, and mobile signals are assigned in 

this band. The radio astronomy allocation and land-mobile is found from 608 to 

614 MHz. Broadcast radio Channels 21–36 occupy frequencies from 512 to 

608 MHz. We see that Channels 27 and 36 are still in the old National 

Television Systems Committee (NTSC) transmission format. Channels 38 to 51 

occupy the spectrum from 614 to 698 MHz. The other utilizations in these 

bands include LPTV, TV translator/booster, low power auxiliary, personal 

radio, and Federal agencies, who use this band for experimental testing and 

evaluation of programs. Radio astronomy research for observing pulsars, the 

sun, the planet Jupiter, the Milky Way galaxy, and observations of spectral 

lines are present. The Department of Veterans Affairs (DVA) uses this band for 

medical telemetry devices. From 746.0 to 756 MHz we see a digitallymodulated signal which is the Verizon Long Term Evolution (LTE) signal.

60-63 793.0–902.0 Most of the signals in these frequencies originate from fixed, mobile, 

aeronautical-mobile and land mobile transmissions with a small primary 

allocation for broadcasting from 805.0 to 806.0 MHz. These bands are used by 

Federal agencies for experimental research and systems shared by public safety

and military agencies. Military agencies operate some radar systems in the 

854.0–902.0 MHz frequency band. There are public safety mobile and control 

channels from 806 to 824 MHz, commercial cellular mobile channels from 824 

to 849 MHz, public safety base station transmit frequencies from 851 to 869 

MHz, and commercial cellular base station transmit frequencies from 869 to 

894 MHz. These figures show heavy usage during our survey.

64, 65 902.0–928.0 Signal allocations in this band are primarily for radiolocation and secondarily 

for amateur radio. The general utilizations for this band are Navy Air & Search, 

surveillance radars on ships and carriers, tracking radars for aeronautical flight 

testing monitor positions of missiles, drones, manned aircraft, security for 

intruder detection, NOAA wind profiler system and this is also one of the ISM

bands. This frequency range was measured using a stepped-spectrum 

measurement algorithm (Figure 65) to detect radar signals and a sweptspectrum measurement algorithm (Figure 64) to detect all other signals. The 

waterfall plot shows constant usage during this spectrum survey.

64, 66 928.0–960.0 Signals in this band are from fixed, land mobile, and broadcasting services. 

General uses in this band include public mobile, aural broadcast auxiliary, fixed 

microwave, low power auxiliary, public safety shared systems, low-capacity 

(voice) systems for Federal agencies, and personal communication systems

(PCS). Military agencies operate some radars in the 935.0–941.0 MHz 

frequency band. These bands show heavy usage during our survey.

66-69 960.0–1215.0 These bands are allocated for aeronautical radionavigation and radionavigation

satellite services and are used by TACAN, Distance Measuring Equipment 

(DME), Air Traffic Control Radar Beacon System (ATCRBS) & Mode-S at 

1030 MHz and 1090 MHz, microwave landing systems (MLS), Traffic Alert 

and Collision Avoidance System (TCAS), Automatic Dependent Surveillance 

Broadcast (ADS-B) at 978 MHz, and Joint Tactical Information Distribution 

System (JTIDS). The GPS-L5 operates in this band at a frequency of 1176.45 

MHz ± 12 MHz. There are space-to-earth and earth-to-space communications 

in this band as well. Some of these frequencies are paired with those in the 

108.0–117.0 MHz band and the 328.0–335.4 MHz band. The frequency gap 

between Figures 66 and 67 is due to the unintentional omission of a band event 

from 962.0 to 971.0 MHz. Signal levels in the GPS L5 band (1164–1188 MHz) 

are as expected.
126

Figure(s)

Frequency 

Range (MHz) Notes

69-71 1215.0–1400.0 These bands contain assignments for earth exploration satellites, radiolocation, 

radionavigation satellites, space research, aeronautical radionavigation, fixed, 

mobile, and land-mobile services. There is also a secondary allocation for 

radiolocation services from 1300.0 to 1350.0 MHz. The general utilizations in 

these bands are GPS-L2, which operates at 1227.6 MHz ± 12 MHz, Wide Area 

Augmentation System (WAAS), High-power long-range surveillance radars, 

FAA operated air-route surveillance radars (ARSR), balloons for drug 

interdiction, SARs, shipborne radars, radio astronomy research, remote sensing, 

fixed-mobile communication links, and GPS at 1381.05 MHz. Personal radio 

exists in the upper part of this band as well as medical telemetry devices, 

wireless communications and earth-to-space fixed satellite. This frequency 

range was measured using a stepped-spectrum measurement algorithm (Figure 

71) to detect radar signals and a swept-spectrum measurement algorithm

(Figures 69 and 70) to detect all other signals. We see radar emissions between 

1230–1390 MHz in Figure 71. One of the individual traces shows that the radar 

was turning on at the time of this measurement. The same radar emission at 

approximately 1334 MHz is visible in Figure 70 in the swept-spectrum 

measurements. Notice that the actual peak power of the radar is not captured in 

the swept-spectrum measurement. Signal levels in the GPS L2 band (1215–

1239 MHz) are as expected.

72, 73 1400.0–1427.0

1427.0–1535.0

The allocation from 1400.0 to 1427.0 is for earth exploration satellites, radio

astronomy, space research applications. This band is a passive band which 

means that it is a receive-only band. We do not know the source of activity 

measured by our survey from 1400 to 1427 MHz.

Services in the frequency range 1427.0–1535.0 MHz include fixed, landmobile, mobile, and mobile satellite services. This band is used for medical 

telemetry and telecommand, fixed telemetry, private land mobile, personal 

radio, wireless communication, aeronautical telemetry, flight testing of 

manned/unmanned aircraft missiles and space vehicles, range safety, aircraft 

chases, and weather data. Frequencies from 1525 to 1535 MHz contain mobilesatellite signals. Most of the activity in this band occurred from approximately 

5000 minutes to 15000 minutes, or from 3.5 days into the measurement to 

about 10.5 days into the measurement.

73, 74 1535.0–1710.0 The allocations in this band are for radionavigation, satellite, radio astronomy, 

space research, meteorological aids and fixed and mobile services. The general 

utilizations are space-to-earth, satellite communications, maritime, aviation,

GPS-L1 (1575.42 MHz ±12 MHz) International Marine/Maritime Satellite 

(INMARSAT) (1626.5–1645.5 MHz), SARSAT, EPIRB and ELT for public 

safety rescue, WAAS, passive remote sensing and passive space research, Deep 

Space Network (DSN), earth-to-space communications, radiosondes, GOES, 

and Television Infrared Operational Satellite (TIROS)-N. In the GPS L1 1559–

1610 MHz Radio Navigation Satellite Service (RNSS) band there is a relatively 

high signal at approximately 1562 MHz (Figure 73).

74, 75 1710.0–1850.0 This frequency range is allocated for fixed, mobile, and space-operations. This 

band is used exclusively by Federal agencies to operate point-to-point 

microwave, tactical radio relay communications systems, mobile subscriber 

equipment, precision-guided munitions (PGM), the Air Force Satellite Control 

Network (AFSCN) & Space-Ground Link System (SGLS), telemetry, and 

telecommand. We saw five signals that were on continuously within the 1755.0 

to 1850.0 MHz band during our survey.
127

Figure(s)

Frequency 

Range (MHz) Notes

75-77 1850.0–2025.0 The main allocation for these bands is fixed and mobile services, however, 

there is a small bandwidth from 2000 to 2020 MHz carved out for mobile 

satellite services; we measured small signal levels at four frequencies. The

entire frequency band allocation is non-Federal and some of the general uses 

are Radio Frequency (RF) devices, personal communications, fixed microwave, 

and earth-to-space satellite communications. Cellular frequencies occupy the 

band from 1850 to 1910 MHz and from 1930 to 1990 MHz and show heavy 

usage. 

77-79 2025.0–2300.0 Federal agencies use this frequency range for space operations, earth 

exploration satellites, fixed and mobile services, and space-research. The nonFederal allocations in the frequency range are fixed and mobile services, 

mobile-satellite, and space research. General uses include TV auxiliary 

broadcasting, cable TV relay, and local TV transmissions. There are research 

and weather satellite systems in this band such as the DSN and the Tracking 

and Data Relay Satellite System (TDRSS). The Western Area Power 

Administration (WAPA) also has assignments in this band. Non-Federal 

allocations include public mobile, wireless communications, and fixed point-topoint microwave links. Our survey measured a mixed pattern of usage 

throughout these bands, including both intermittent and continuous signals.

79, 80 2300.0–2500.0 Signals from radiolocation, fixed and mobile services, broadcasting satellites, 

satellite radiolocation, amateur, mobile satellites, and radiodetermination 

satellites occupy this frequency range. General uses in this band are amateur 

radio, high-power long range surveillance radar, air-traffic control radars, 

telemetry, WAPA, research and developmental testing, ISM equipment (such 

as microwaves), downlinks, and the Arecibo radar (which operates from 2370

to 2390 MHz). There are wireless communications in this band, military 

tactical communications, TV auxiliary broadcasting, private land mobile, fixed 

microwave, scientific balloon-borne payloads, Radio Frequency Identification 

(RFID), and U.S. Coast Guard crew communications. In the graph we see 

different characteristics for the signals transmitting from 2485.0 to 2495.0 MHz 

than for signals from 2340.0 to 2485.0 MHz.

80, 81 2500.0–2700.0 These bands are allocated for fixed and mobile services, broadcasting, earth 

exploration, fixed and mobile satellites, radio astronomy applications, and

space-research. The general utilizations in these bands are wireless 

communications, military tactical communications, NASA-research on global 

environmental changes and downlinks, earth exploration satellite, passive space 

research, radio astronomy. Most of these signals appear to be digitally 

modulated.

82 2700.0–2900.0 The only allocations in this frequency range are for aeronautical 

radionavigation services and meteorological aids. Airport Surveillance Radars 

(ASRs) and Next-Generation Radar (NEXRAD) weather radars operate in this 

band and there is some radio astronomy research in this band. The graphs 

shown on this page show a radar that switched to a different channel while we 

were at the measurement location. This measurement was taken using the 

stepped-spectrum algorithm used to detect radars. There are several distinct 

frequencies that show activity in this band in the Denver metropolitan area. 

They are at 2760 MHz, 2785 MHz, and 2825 MHz.
128

Figure(s)

Frequency 

Range (MHz) Notes

83-88, 92 2900.0–3700.0 Radiolocation, maritime and aeronautical radionavigation, and fixed services 

and fixed satellite services are assigned to this band. There are secondary 

allocations from 3100.0 to 3300.0 MHz for earth exploration satellites and 

space research. The general utilizations are maritime radars, military highpower radars, long-range surveillance radars, private land mobile, SARS, 

amateur radio, and satellite communications. Swept measurements (Figures 83-

88) were made from 2900.0 to 3700.0 MHz and stepped-spectrum 

measurements (Figure 92) were made from 2900.0 to 3650.0 MHz (a radar 

band). The swept measurements showed little activity; we see only one trace 

where activity was prevalent in Figure 92. In the frequency range from 3100 to 

3600 MHz, the spectrum appears mostly inactive using the swept-frequency 

algorithm, but shows one distinct trace with activity and for the rest of the 

traces shows low-level frequency activity when measured using the steppedspectrum algorithm. This demonstrates how different measurement techniques 

can impact our understanding of the signals that occupy the spectrum.

89-91 3700.0–4200.0 The allocations in this frequency range include fixed, fixed-satellite, and 

mobile. Satellite communications, fixed microwave and reception of downlinks 

are the general utilizations for this band. The downlink signals are paired with 

transmission of uplink signals from 5925 to 6425 MHz. We measured little 

activity in these bands.

93, 95 4200.0–4400.0 The only allocation in this band is for aeronautical radionavigation services. 

CW and pulsed radar altimeters are used in this band. We measured these 

altimeters while conducting an azimuthal-scan in the 4000–5000 MHz band. 

Figure 93 shows the altimeter signals in the 4000–5000 MHz band with other 

signals and Figure 94 shows a close-up of an altimeter band from 4200 to 4400 

MHz. Our zero-degree position in Figure 94 was lined up with magnetic north, 

whereas the Google Earth©images in Figures C-1 and C-5 in Appendix C are 

aligned to true north. The declination during this measurement was 

approximately 9°. The measured signals appear at approximately 10° which 

would correspond to altimeter readings that may have come from Rocky 

Mountain metropolitan airport in Broomfield, CO. The measured signals 

located between 70° and 110° correspond to altimeters that may be located at 

Denver International Airport in Denver, CO. We believe these are altimeters 

because they appear between 4250 MHz and 4350 MHz.

93, 96 4400.0–5000.0 The allocations in this frequency range are for fixed, mobile, and fixed satellite 

services, radio astronomy, and space research. There is a 10 MHz allocation 

from 4990 to 5000 MHz for “RADIO ASTRONOMY” for passive space 

research. The general uses are tactical systems for point-to-point, line-of-sight 

and troposcatter communications, unmanned aerial video downlinks, space-toearth communications, public safety land mobile, drug interdiction, radio 

astronomy, passive environmental change observations and measurements, 

radio astronomy, and very long baseline interferometry. There are few detected 

signals in this band in the Denver metropolitan area.

97 5000.0–5250.0 The allocations for this frequency range are aeronautical radionavigation and 

mobile services, radionavigation and fixed satellite services, and mobile

communications. The general uses in this band are aviation, satellite 

communications. The FAA and the military use this band for the MLS and the 

Airport Network and Location Equipment (ANLE) system. The ANLE is a 

high-integrity, high data-rate wireless local area network (WLAN). RF devices 

also have assignments in this band. We measured a distinct continuous-use 

signal at approximately 5190 MHz.
129

Figure(s)

Frequency 

Range (MHz) Notes

97, 98, 100 5250.0–5925.0 This frequency range is allocated for earth exploration and fixed satellite

services, radiolocation, space research, aeronautical and maritime 

radionavigation, meteorological aids, and mobile services. The secondary 

allocations from 5650.0 to 5925.0 MHz are for amateur and amateur satellite

services. The general utilizations in this band are for RF devices, private land 

mobile, military radars, space-based observations, SARs, active radio 

astronomy research, aviation, ground-based meteorological radars, maritime 

communications, Terminal Doppler Weather Radar (TDWR) systems, ISM 

equipment, amateur radio, and personal radio. This area of the spectrum was 

also measured using the stepped-spectrum algorithm as shown in Figure 100. 

The signals at approximately 5520, 5615, 5725, and 5850 MHz shown in the 

swept-spectrum measurements of Figures 97 and 98 show up in the steppedspectrum measurements of Figure 100 as well.

98-103 5925.0–7250.0 The allocations across this frequency range are for fixed, fixed satellite, and 

mobile services. The general utilizations in this band are earth-to-space satellite 

communications, fixed point-to-point microwave, Federal civilian and military 

satellite communication uplinks (paired with 3700–4200 MHz), TV broadcast 

auxiliary, cable TV relay, remote sensing (6425–7250 MHz), radio astronomy 

(6668.518 MHz). Federal agencies use the band from 7125 to 7250 MHz for 

point-to-point microwave communications, weather, vessel traffic, 

hydroelectric and space research (7190–7235 MHz). Figures 101 and 103 show 

azimuth-scanning measurements. True point-to-point links appear as small dots 

on the plot at several angles but one frequency. Other transmission types, such 

as digital signals, show strong signals at all angles within some frequency span. 

Microwave links have low power that is not measured by the swept-spectrum 

algorithm; we would expect the point-to-point links captured in Figures 101

and 103 to be transmitting all of the time.

102-107 7250.0–8500.0 Most of the allocations across these frequency bands are for Federal 

assignments and include fixed, mobile, earth exploration and meteorological 

satellites, and space research. The secondary allocations are for fixed services 

and mobile satellite services. Non-federal allocations are for space research.

The general utilizations for these bands are space-to-earth communications, 

Defense Satellite Communications Systems (DSCS), fixed point-to-point 

microwave systems, weather, vessel traffic, hydroelectric and space research, 

Wideband Gapfiller Satellite (WGS), GOES, TTC data downlinks from nongeostationary satellites, long-range radars, deep space probes communications. 

The measurements were taken using both swept-spectrum methods (Figures 

102, 104, and 106) and azimuth-scanning measurements (Figures 103, 105 and 

107). We measured very little activity in these bands.

106-109 8500.0–10000.0 In this final measured frequency range, the allocations are for radiolocation,

aeronautical and maritime radionavigation, and radionavigation services. 

Secondary allocations are for radiolocation and meteorological aids. The 

general utilizations are military and non-military radar systems, private land 

mobile, earth-exploration satellites from 8550 to 8650 MHz, search and rescue, 

law enforcement, navigation, surveillance, avian detectors, airport surface 

detection, maritime harbor and coastal traffic, meteorological radars, airborne 

radars to research convective storm and mesoscale phenomena, and SARs. 

Measurements in these bands were taken using the swept-spectrum techniques

(Figures 106 and 108), stepped-spectrum methods (Figure 109), and azimuthscanning methods (Figure 107). Activity was measured at 9370 MHz using 

both swept- and stepped-spectrum methods.
130

4 ACKNOWLEDGEMENTS 

We acknowledge Frank Sanders for many conversations regarding spectrum assignments and 

allocations. His prior reports on spectrum surveys served as invaluable references for this work. 

We also thank Eric Nelson, our Division Chief, for his leadership and guidance during the 

process of writing this report. 
131

5 REFERENCES 

[1] U.S. Department of Commerce, National Telecommunications and Information 

Administration, (NTIA), Manual of Regulations and Procedures for Federal Radio 

Frequency Management, Chapter 2, Washington, D.C., revised May 2013.

http://www.ntia.doc.gov/page/2011/manual-regulations-and-procedures-federal-radiofrequency-management-redbook

[2] United States Department of Commerce, Department Organization Order 25-7, 

http://www.osec.doc.gov/opog/dmp/doos/doo25_7.html

[3] Frank Sanders, Vincent Lawrence, and Robert Hinkle, “Broadband Spectrum Survey at 

Denver, Colorado,” NTIA Report TR-95-321, September 1995, 

http://www.its.bldrdoc.gov/publications/2353.aspx 

[4] F.H. Sanders, B.J. Ramsey, and V.S. Lawrence, “Broadband Spectrum Survey at Los 

Angeles, California,” NTIA Report TR-97-336, May 1997, 

http://www.its.bldrdoc.gov/publications/2368.aspx

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

California,” NTIA Report TR-97-334, December 1996. 

http://www.its.bldrdoc.gov/publications/2366.aspx 

[6] F.H. Sanders, B.J. Ramsey, and V.S. Lawrence, “Broadband Spectrum Survey at San 

Francisco, California,” NTIA Report TR-99-367, July 1999. 

http://www.its.bldrdoc.gov/publications/2398.aspx

[7] F.H. Sanders, G. R. Hand, and V. S. Lawrence, “Land mobile radio channel usage 

measurements at the 1996 Summer Olympic Games,” NTIA Report TR-98-357, Sep. 1998. 

http://www.its.bldrdoc.gov/publications/2388.aspx 

[8] NTIA, “United States Frequency Allocation Chart,” http://ntia.doc.gov/page/2011/unitedstates-frequency-allocation-chart. 

[9] J.R. Hoffman, R.J. Matheson, and R.A. Dalke, “Measurements to characterize land mobile 

channel occupancy for Federal bands 162-174 and 406-420 MHz in the Washington, D.C., 

area,” NTIA Report TR-07-448, July 2007, 

http://www.its.bldrdoc.gov/publications/2485.aspx. 

[10] 47 C.F.R. § 2.106 Table of Frequency Allocations (2012). http://www.ecfr.gov/cgibin/retrieveECFR?gp&n=47y1.0.1.1.3.2&r=SUBPART&ty=HTML#47:1.0.1.1.3.2.216.7 

[11] NTIA, “Federal Spectrum Use Summary,” June 2010, 

http://www.ntia.doc.gov/files/ntia/Spectrum_Use_Summary_Master-06212010.pdf. 
132

APPENDIX A: EXPLANATION OF MEASUREMENT GRAPHS 

There are many ways to process and present the data acquired during spectrum surveys. In this 

section, three methods employed at ITS during this survey will be discussed. 

A.1 Maximum-Mean-Median-Minimum (M4) plots 

The M4 plots (top graph of Figure 3 in Section 3) show the maximum, mean,4 median, and 

minimum values at each frequency, and are calculated using internal MATLAB®

scripts. The 

measured data are expressed in field strength (dBμV/m), referenced to the input of a 0 dBi 

antenna versus frequency. The measured data is corrected using the system gain and the antenna 

correction factor (ACF). The system gain and noise figure are obtained by performing 

calibrations periodically throughout the measurement series. The mean system noise (magenta 

line) is produced using the noise figure from the calibrations. 

A.2 Time vs. Frequency Plots 

Time vs. frequency (waterfall) plots are displayed using a contour plot as shown by the middle 

plot of Figure 3. The generation of waterfall plots is time and memory intensive due to the large 

array sizes. This array is decimated by determining the median measurement time between each 

scheduled measurement and retaining the maximum power trace for that time interval. The time 

axis displays the total measurement time for all traces in minutes. The maximum value of this 

axis will vary depending on the number of times the event was measured. The data spacing 

stated at the top of the graph refers to the median number of minutes between measured events. 

For the data shown in Figure 3, the median time is 16.4 minutes, which means the data was 

measured approximately every 16.4 minutes. The threshold, shown in the bottom plot, 

determines the lowest field strength level in decibel-microvolts per meter (dBμV/m) at which 

data will be displayed in the time-varying plot. If the measured field strength does not exceed the 

threshold, the data point will not be displayed (it will be rendered as a white point). If the data 

exceeds the threshold, the color of the data point represents the amplitude of the field strength—

blue represents the lowest field strength and red represents highest field strength. The time scale 

creates a linear time vector using the median time spacing for the time interval mentioned above. 

The threshold is determined by one of two methods. One method requires a statistical analysis of 

the system noise. With this technique the threshold is set to a field strength level at which the 

system noise is likely to exceed the threshold 0.01% of the time. The second method is 

determined by first processing the data into M4 plots and examining the maximum value of the 

trace at frequencies that appear to be free of signals. The threshold level is then set to this 

maximum level. 

 

4

 The mean is taken by converting power values to linear form. The mean of these linear values is determined and 

then converted back to power and then into field strength in dBμV/m. 
133

A.3 Field-Strength, Complementary Cumulative Distribution Function (FS-CCDF) Plots 

When measurement system components (amplifiers, switches, filters, SAs) perform consistently 

over the course of a measurement, the statistical characteristics of the system noise remain 

stationary with regard to the mean, variance, and power distribution. Though noise is a random 

process, its consistent statistical characteristics provide a useful way to differentiate system noise 

from signals, especially when the signal power is very close to the mean power of the system 

noise. Signals will have statistical characteristics that are different from those of noise. 

In this report, we plot the FS-CCDFs as shown by the bottom graph in Figure 3. These plots are 

useful for differentiating between intentionally-radiated signals and impulsive or Gaussian noise, 

quickly characterizing signals, and identifying low-level signals—something that is not generally 

possible with other processing methods.5

For these types of graphs, we begin by constructing the 

probability density function (PDF) of the measured data. In the current software, the measured 

data is binned into 0.1 dB power bins. From the PDF, we compute the cumulative distribution 

function (CDF), and the complementary cumulative distribution function (CCDF) vs. power in 

dBm.6From the CCDF shown in Figure A-1, we choose equally spaced values along the x-axis 

to obtain values of power or field strength at the input to the antenna on the y-axis. We also 

choose the spacing so that we get probabilities close to 0.1%, 2%, 50%, and 95%. By choosing 

equally-spaced x-values, it is possible to scale the y-axis so that sample-detected, Gaussian 

system noise is displayed as a straight line. The chosen values are converted to a percent 

probability. Finally, at each frequency, we display the probability that the power (dBm) or field 

strength (dBμV) on the y-axis is exceeded, as shown in Figure A-2 or the figures in the report. 

Because this is a cumulative distribution at each frequency, the probability value gives us an 

indication of the percentage of time that the signal appeared above certain power levels during 

the measurement. For other signal types, the spacing of the power or field strength values will be 

indicative of the signal type or the type of detector used to measure the signal. For example, 

median-of-five processed Gaussian noise (Figure 42, 411.2–411.3 MHz) show a probabilitylevel spacing of approximately one dB (Figure A-2). RMS-detected Gaussian noise (Figure 69, 

1210–1230 MHz) show the lower-probability levels (0.09% to 2.02%) more widely spaced than 

higher probability levels (93.30% to 96.18%) (Figure A-2).

 

5

 M. Cotton, R. Achatz, J. Wepman, B. Bedford, “Interference Potential of Ultrawideband Signals: Part 1 – 

Procedures to characterize ultrawideband emissions and measure interference susceptibility of C-band satellite 

digital television receivers ”, NTIA-TR-05-419, Appendix D, Feb., 2005. 

6

 CCDF’s are calculated using powers which are then converted to field strength in dBμV/m for the final plots. 
134

Figure A-1. Complementary cumulative distribution function (CCDF) at 116.00 MHz. 

Figure A-2. Inverse complementary cumulative distribution function. The percent probability is 

shown along the x-axis and the power is shown along the y-axis. 
135

Figure A-3. Close-in view of one-dB probability spacing for median-of-five processed Gaussian 

noise shown inside the dashed rectangle for the frequency range from 411.2 to 411.4 MHz. 

Figure A-4. Close-in view of variable probability spacing for RMS-detected Gaussian noise 

shown inside the dashed rectangle for the frequency range from 1210 to 1230 MHz. 
136

APPENDIX B: RADIO SPECTRUM MEASUREMENT SCIENCES (RSMS) SYSTEM 

The NTIA RSMS-4 truck is a self-contained vehicle used to transport equipment to locations to 

perform spectrum surveys or detailed studies of various radio services. This vehicle, shown in 

Figure B-1, is approximately 4.8 m (16 ft.) long, has a gross weight of 11.6 t (12.75 ST), and is 

wired for 100-amp electrical service. 

A two-layer design provides approximately 60 dB of shielding from outside radio sources. The 

outside skin is a riveted cage of 28.6 mm (1⁄8 in.) thick aluminum with fully welded seams. The 

wiring and conduit are surface mounted and do not pierce the skin. Bulkhead feed-throughs 

provide access to the masts on the exterior of the truck. The doorway is equipped with finger 

stock to ensure good electrical contact to improve shielding effectiveness. The masts can be 

extended to a height of 9.1 m (30 ft.) using an internal compressor. Air conditioning provides a 

constant temperature environment. A 20 kilowatt (kW) generator can be used to supply power 

for the truck when there are no power sources available. The generator runs off two 100-gallon 

fuel tanks. The truck can run 24 hours a day for approximately 11⁄2 weeks before refueling. When 

a nearby power source is available, a 15 m (50 ft.) electrical cable with optional 15 m (50 ft.) 

extension can be used to connect to the source. 

Measurement and processing equipment is placed in three slide-mounted racks each with its own 

uninterruptible power supply (UPS). Equipment for this spectrum survey is shown in Figure B-2. 

Additional storage is provided in compartments in the truck. An emergency escape is located on 

the side of the truck and is also shielded. A winch can be used to lift equipment onto the roof of 

the truck. A safe is located in one of the upright storage cabinets. Interior lighting consists of one 

overhead and one wall-mounted fluorescent fixture and three direct current (DC)-powered dome 

lights. Track lighting is installed in front of the equipment racks. A smoke/carbon monoxide 

detector and fire extinguisher are located in the truck at all times. A schematic of the RSMS 

truck is shown in Figure B-3. 
137

Figure B-1. RSMS-4 measurement truck with mast-mounted antennas and preselector units. 

Figure B-2. Measurement equipment setup inside RSMS-4 truck. The LMR system makes 

measurements in the LMR bands and the broad-frequency systems measures all frequencies 

above 500 MHz and some bands not covered by the LMR bands 
138

Figure B-3. Detailed schematics of the RSMS truck. 
139

APPENDIX C: STATIC VS. MOBILE MEASUREMENTS

We would like to understand how static spectrum occupancy measurements compare to mobile 

measurements. We also want to understand how a measurement on a hilltop compares to a 

mobile measurement that covered the city of Denver. We present data for the static spectrum 

survey conducted from a hilltop, data collected around the immediate measurement site, and data 

collected over the city of Denver. We also show the spectrum occupancy measurement data at 

discrete time intervals to show the build-up of signals and approximately how long a 

measurement might take to acquire a large portion of the transmitted signals. We chose the LMR 

band from 406 to 420 MHz for this study. 

C.1 Mobile Measurements in the Denver/Boulder Metropolitan Areas 

Figure C-1 shows the route chosen for a mobile measurement in the Denver Metropolitan area. A 

GPS tracker is used to mark the route which is then imported into Google Earth© maps. Shown 

on this map are some key landmarks. The first is the location of the Arvada measurement site 

shown in about the middle of the map. Downtown Denver and the Denver International Airport 

(DIA) are labeled on the map as well. Other key locations are the Denver Federal Center and 

Buckley Air Force Base. The drive-path direction is shown by the white arrows and an 

explanation follows. 

Figure C-1. Mobile measurement route for Denver/Boulder Metropolitan Areas. 
140

We started driving in Boulder and drove down Highway 93 toward Golden. We then drove 

around the perimeter of the Denver Federal Center and headed north toward the Arvada 

measurement location. From Arvada we drove toward downtown Denver and drove some of 

these streets and then headed toward Buckley Air National Guard/Air Force Base. From this 

location we headed north toward DIA, turned left on 104th Ave and then headed north on 

Colorado Blvd. and then took Highway 7 toward Boulder to end the day. 

Cumulative measurement results for this route are shown in Figures C-2–C-4. The first band 

measured is 406–411 MHz, the second band measured is 411–416 MHz, and the last band 

measured is 416–420 MHz. The signals from the 406–411 MHz band are LMR control channels 

and were on during the entire drive across the Denver Metropolitan area. We see that the median 

time in the waterfall plot was 1.65 minutes and that the entire drive took approximately 400 

minutes or almost seven hours. 
141

Figure C-2. Mobile measurements from 406 to 411 MHz in the Denver Metropolitan area. 
142

Figure C-3. Mobile measurements from 411 to 416 MHz in the Denver Metropolitan area. 
143

Figure C-4. Mobile measurements from 416 to 420 MHz in the Denver Metropolitan area. 
144

C.2 Mobile Measurements around the Arvada Spectrum Survey Site 

Figure C-5 shows the route chosen for a mobile measurement in the immediate vicinity of our 

location in Arvada, CO. We use a GPS tracker and then import the route into Google Earth©

maps. Shown on this map is the location of the NTIA labs in Boulder, where we started and 

finished the measurement. Also shown is the Arvada spectrum survey site. We wanted to 

measure only signals around the Arvada site, so we traveled on rural and suburban streets around 

Arvada. 

Figure C-5. Mobile measurement route for the Arvada suburbs. 

Cumulative measurements at the Arvada location are shown in Figures C-6–C-8. The median 

time is 1.65 minutes and the total measurement time is approximately 175 minutes or almost 

three hours. For the most part, we see that many of the signals present in the Denver mobile 

measurements are present in these measurements. One major difference in these measurements is 

that some type of impulsive signal (0.09% trace separated from all other traces) was present 

across all three bands in the Arvada measurements. Both data sets were processed using the same 

methods, so at present this difference is being studied.
145

Figure C-6. Mobile measurements from 406 to 411 MHz around the Arvada spectrum survey site. 
146

Figure C-7. Mobile measurements from 411 to 416 MHz around the Arvada spectrum survey site. 
147

Figure C-8. Mobile measurements from 416 to 420 MHz around the Arvada spectrum survey site. 
148

C.3 Static Measurements at the Arvada Measurement Site 

We processed data in different time slots for the spectrum occupancy measurements shown in 

Figures 41–43. These plots have been duplicated in Figures C-14, C-19, and C-24. We wanted to 

investigate signals that appear during certain periods of time and compare them to the mobile 

measurements. We broke the static measurements into time slots. Measurements were made from 

June 1 to 29, 2011. We processed data for a random two week period from June 15 to 29, 2011. 

Within this two-week period, we processed data from June 17 to 24, 2011. During this weeklong period, we processed data for a day-long period on June 19, 2011 and finally, we processed 

data on this day for a one-hour period from 7 a.m. to 8 a.m. All of these choices were random. A 

schematic of this is shown in Figure C-9. 

Figure C-9.Time slices chosen for processed data from the Denver spectrum survey in June 

2011.

The results of this time slice processing are shown in Figures C-10–C-24. Figures C-10–C-14

show the results for the 406–411 MHz frequency band. Figure C-10 shows results for the 

one-hour time slice which shows a total of 31 frequencies that were acquired during this hour. 

Results for one day are shown in Figure C-11, showing an additional 15 frequencies captured 

during the day. An additional eight frequencies appear during the week as shown in Figure C-12.
149

One additional frequency appears during the two-week period, shown in Figure C-13, and four 

additional frequencies appear during the entire month as shown in Figure C-14. 

Results for the frequency band 411–416 MHz are shown in Figures C-15–C-19. Six frequencies 

are shown during the one-hour time slice in Figure C-15. Transmissions from two large signals 

and several smaller signals are added to this frequency band during the day as shown in Figure 

C-16. Seven additional frequencies are transmitted during the week-long period as shown in 

Figure C-17. Figure C-18 shows results from the two-week period where an additional nine 

transmission signals are added to this frequency band. From two weeks to four weeks (Figure C19), an additional five transmissions are added to this frequency data. 

Figures C-20–C-24 show results for the frequency band 416–420 MHz. During a one-hour time 

slice, Figure C-20, six frequencies appear on the plot. Figure C-21 shows results for transmission 

received during the day in which at least nine new frequency transmissions appear. During the 

one-week period, 28 additional frequency transmissions are received as shown in Figure C-22. 

At least four more transmissions are recorded and a definite pattern begins to emerge from the 

noise on the waterfall plot from 419.5 to 420 MHz after an additional week (Figure C-23). 

Finally, from two weeks to four weeks, shown in Figure C-24, a few new signals appear between 

418 MHz and 418.5 MHz, and a much broader signal appears in the waterfall plot between 419 

MHz and 420 MHz. 

C.4 Comparisons between Mobile and Static Measurements 

In the 406–411 MHz frequency band, it appears as though measurements processed during a 

one-day time slice (Figure C-11) are comparable to measurements taken in the two mobile 

measurement scenarios (Figures C-2 and C-6). The characteristics of the signals may change; 

however, the frequency of transmission appears to be similar. 

It appears as though many transmissions collected for the mobile measurements compare well 

with those measured in the one-week to two-week time slices for the frequencies from 411 to 

416 MHz. The transmissions appear to differ both in field-strength levels and in the clusters of 

frequencies that appear. These transmissions are shown in Figures C-3, C-7, C-17 and C-18.

Some of the same signals appear in the three different measurements made in the 416–420 MHz 

band as shown in Figures C-4, C-8, and -21. A similar number of signals are shown in these 

three figures which is understandable since Figure C-21 shows signals for a one-day 

measurement. A few of the signal characteristics are different for the mobile measurements made 

across the Denver Metropolitan area.
150

Figure C-10. Static spectrum survey measurements from 406 to 411 MHz processed over a one-hour time slice. 
151

Figure C-11. Static spectrum survey measurements from 406 to 411 MHz processed over a one-day time slice. 
152

Figure C-12. Static spectrum survey measurements from 406 to 411 MHz processed over a one-week time slice. 
153

Figure C-13. Static spectrum survey measurements from 406 to 411 MHz processed over a two-week time slice. 
154

Figure C-14. Static spectrum survey measurements from 406 to 411 MHz processed over a one-month time slice. 
155

Figure C-15. Static spectrum survey measurements from 411 to 416 MHz processed over a one-hour time slice. 
156

Figure C-16. Static spectrum survey measurements from 411 to 416 MHz processed over a one-day time slice. 
157

Figure C-17. Static spectrum survey measurements from 411 to 416 MHz processed over a one-week time slice. 
158

Figure C-18. Static spectrum survey measurements from 411 to 416 MHz processed over a two-week time slice. 
159

Figure C-19. Static spectrum survey measurements from 411 to 416 MHz processed over a one-month time slice. 
160

Figure C-20. Static spectrum survey measurements from 416 to 420 MHz processed over a one-hour time slice. 
161

Figure C-21. Static spectrum survey measurements from 416 to 420 MHz processed over a one-day time slice. 
162

Figure C-22. Static spectrum survey measurements from 416 to 420 MHz processed over a one-week time slice. 
163

Figure C-23. Static spectrum survey measurements from 416 to 420 MHz processed over a two-week time slice. 
164

Figure C-24. Static spectrum survey measurements from 416 to 420 MHz processed over a one-month time slice. 
FORM NTIA-29 U.S. DEPARTMENT OF COMMERCE 

(4-80) NAT’L. TELECOMMUNICATIONS AND INFORMATION ADMINISTRATION

BIBLIOGRAPHIC DATA SHEET

1. PUBLICATION NO.

TR-13-496

2. Government Accession No. 3. Recipient’s Accession No.

4. TITLE AND SUBTITLE

Broadband Spectrum Survey in the Denver and Boulder, Colorado, Metropolitan Areas

5. Publication Date

August 2013

6. Performing Organization Code

NTIA/ITS.M

7. AUTHOR(S)

Chriss Hammerschmidt, Heather E. Ottke, J. Randy Hoffman

9. Project/Task/Work Unit No.

3154011-300

8. PERFORMING ORGANIZATION NAME AND ADDRESS

Institute for Telecommunication Sciences

National Telecommunications & Information Administration

U.S. Department of Commerce

325 Broadway

Boulder, CO 80305

10. Contract/Grant Number.

11. Sponsoring Organization Name and Address

National Telecommunications & Information Administration

Herbert C. Hoover Building

14th & Constitution Ave., NW

Washington, DC 20230

12. Type of Report and Period Covered

14. SUPPLEMENTARY NOTES

15. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant bibliography or 

literature survey, mention it here.)

NTIA is responsible for managing the Federal Government’s use of the radio spectrum. In discharging this responsibility, 

NTIA uses the Radio Spectrum Measurement Sciences system to collect spectrum occupancy data for radio frequency 

assessments. This report shows measured frequency data spanning spectrum from 108 MHz to 10 GHz in the metropolitan 

area of Denver, Colorado, during the month of June 2011.

16. Key Words (Alphabetical order, separated by semicolons)

land mobile radio (LMR); radar emission spectrum; radio spectrum measurements sciences (RSMS); radio frequency 

environment; spectrum occupancy; spectrum resource assessment; spectrum survey

17. AVAILABILITY STATEMENT

UNLIMITED.

FOR OFFICIAL DISTRIBUTION.

18. Security Class. (This report)

Unclassified

20. Number of pages

189

19. Security Class. (This page)

Unclassified

21. Price:


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