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11-2 Section Eleven

In This Section:

Chapter 11.1: The Electromagnetic Spectrum

11-9

Introduction

11-9

Spectral Sub-Regions

11-10

Optical Spectrum

11-10

Visible Light Band

11-10

IR Band

11-11

UV Band

11-12

DC to Light

11-12

Microwave Band

11-12

Radio Frequency (RF) Band

11-13

Power Frequency (PF)/Telephone Band

11-13

Frequency Band Designations

11-13

Light to Gamma Rays

11-16

X Ray Band

11-16

Gamma Ray Band

11-18

Bibliography

11-18

Chapter 11.2: Propagation

11-21

Introduction

11-21

Propagation in Free Space

11-21

Transmission Loss Between Antennas in Free Space

11-23

Propagation Over Plane Earth

11-25

Field Strengths Over Plane Earth

11-25

Transmission Loss Between Antennas Over Plane Earth

11-29

Propagation Over Smooth Spherical Earth

11-30

Propagation Beyond the Line of Sight

11-30

Effects of Hills, Buildings, Vegetation, and the Atmosphere

11-33

Effects of Hills

11-35

Effects of Buildings

11-38

Effects of Trees and Other Vegetation

11-41

Effects of the Lower Atmosphere (Troposphere)

11-41

Stratification and Ducts

11-42

Tropospheric Scatter

11-42

Atmospheric Fading

11-43

Effects of the Upper Atmosphere (Ionosphere)

11-43

References

11-44

Chapter 11.3: Radio Broadcasting

11-47

Introduction

11-47

Standard Broadcasting

11-47

Modulation Techniques

11-47

Modulation of the AM Carrier Wave

11-48

Channel and Station Classifications

11-49

Field Strength

11-49

Propagation

11-50

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Broadcast Transmission Systems 11-3

Transmitters

11-50

High-Level AM Modulation

11-50

Pulse-Width Modulation

11-51

Solid-State Transmitters

11-53

FM Broadcasting

11-55

Frequency Modulation

11-56

FM Broadcast Modulation Techniques

11-56

Modulation Circuits

11-56

Subsidiary Communications Authorization (SCA)

11-57

Frequency Allocations

11-58

Transmitters

11-59

FM Power Amplifiers

11-59

Tuning the Cavity

11-60

Transmitter Performance and Maintenance

11-60

Key System Measurements

11-61

Synchronous AM in FM Systems

11-61

Incidental Phase Modulation

11-62

Bibliography

11-63

Chapter 11.4: Radio STL Systems

11-65

Introduction

11-65

Radio vs. Landline Links

11-65

STL System Configuration

11-67

Digital STL vs. Analog STL Link

11-69

Digital STL Performance

11-71

Coding System

11-72

Analog Composite STL Transmitter and Receiver Characteristics

11-73

Components of an STL System

11-73

Transmitter and Receiver Requirements

11-74

Transmission Lines

11-77

Antenna System

11-80

Mounting Structures

11-81

Hardware Considerations

11-81

System Planning

11-82

Frequency Selection

11-83

Spectrum Considerations

11-83

Path Layout

11-83

Line of Sight

11-84

STL Site Selection

11-84

Terrain Considerations

11-84

Path Reliability

11-86

Dealing with Problem Paths

11-91

Hot-Standby Redundant Systems

11-91

Pre-Installation Checkout

11-93

Planning Cable Runs

11-97

Installation

11-97

Checking System Operation

11-99

Troubleshooting

11-99

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11-4 Section Eleven

Operating the System

11-99

References

11-100

Bibliography

11-100

Chapter 11.5: Transmitting Antennas

11-103

Introduction

11-103

Operating Characteristics

11-103

Antenna Bandwidth

11-104

Polarization

11-105

Antenna Beamwidth

11-105

Antenna Gain

11-105

Space Regions

11-106

Impedance Matching

11-107

L Network

11-107

Tee Network

11-107

Pi Network

11-108

Line Stretcher

11-109

Antenna Types

11-111

Quarter-Wave Monopole

11-112

Log-Periodic Antenna

11-112

Yagi-Uda Antenna

11-113

Waveguide Antenna

11-113

Horn Antenna

11-114

Reflector Antenna

11-114

Spiral Antenna

11-115

Array Antenna

11-115

AM Broadcast Antenna Systems

11-116

Directional AM Antenna Design

11-116

Antenna Pattern Design

11-117

Bearing

11-120

Antenna Monitoring System

11-120

Phase/Current Sample Loop

11-120

Sample lines

11-121

The Common Point

11-121

Monitor Points

11-122

Folded Unipole Antenna

11-123

FM Broadcast Antenna Systems

11-123

Antenna Types

11-124

Bibliography

11-126

Chapter 11.6: RF Combiner and Diplexer Systems

11-127

Introduction

11-127

Passive Filters

11-127

Filter Type

11-128

Filter Alignment

11-128

Filter Order

11-129

Four-Port Hybrid Combiner

11-130

Microwave Combiners

11-134

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Broadcast Transmission Systems 11-5

Hot Switching Combiners

11-136

High-Power Isolators

11-138

Theory of Operation

11-139

Applications

11-140

Hot Switch

11-141

Diplexer

11-141

Multiplexer

11-142

References

11-142

Bibliography

11-143

On the CD-ROM:

“Audio Tests and Measurements” by Richard Cabot, an archive chapter from the first edition
of the Audio Engineering Handbook. This chapter provides an extensive overview of audio
test and measurement techniques.

Reference Documents for this Section

Bean, B. R., and E. J. Dutton: “Radio Meteorology,” National Bureau of Standards Monograph

92, March 1, 1966.

Benson, B., and Whitaker, J.: Television and Audio Handbook for Technicians and Engineers,

McGraw-Hill, New York, N.Y., 1989.

Bingeman, Grant: “AM Tower Impedance Matching,” Broadcast Engineering, Intertec Publish-

ing, Overland Park, Kan., July 1985.

Bixby, Jeffrey: “AM DAs—Doing it Right," Broadcast Engineering, Intertec Publishing, Over-

land Park, Kan., February 1984.

Bordonaro, Dominic: “Reducing IPM in AM Transmitters,” Broadcast Engineering, Intertec

Publishing, Overland Park, Kan. May 1988.

Bullington, K.: “Radio Propagation at Frequencies above 30 Mc,” Proc. IRE, pg. 1122, October

1947.

Bullington, K.: “Radio Propagation Variations at VHF and UHF,” Proc. IRE, pg. 27, January

1950.

Burrows, C. R., and M. C. Gray: “The Effect of the Earth’s Curvature on Groundwave Propaga-

tion,” Proc. IRE, pg. 16, January 1941.

Chick, Elton B.: “Monitoring Directional Antennas,” Broadcast Engineering, Intertec Publish-

ing, Overland Park, Kan., July 1985.

Collocott, T. C., A. B. Dobson, and W. R. Chambers (eds.): Dictionary of Science & Technology.

Crutchfield, E. B. (ed): NAB Engineering Handbook, 8th ed., National Association of Broadcast-

ers, Washington, D.C., 1992.

DeComier, Bill: “Inside FM Multiplexer Systems,” Broadcast Engineering, Intertec Publishing,

Overland Park, Kan., May 1988.

de Lisle, E. W.: “Computations of VHF and UHF Propagation for Radio Relay Applications,”

RCA, Report by International Division, New York, N.Y.

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Broadcast Transmission Systems


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11-6 Section Eleven

Dickson, F. H., J. J. Egli, J. W. Herbstreit, and G. S. Wickizer: “Large Reductions of VHF Trans-

mission Loss and Fading by the Presence of a Mountain Obstacle in Beyond-Line-of-Sight
Paths,” Proc. IRE, vol. 41, no. 8, pg. 96, August 1953.

“Documents of the XVth Plenary Assembly,” CCIR Report 238, vol. 5, Geneva, 1982.

“Documents of the XVth Plenary Assembly,” CCIR Report 563, vol. 5, Geneva, 1982.

“Documents of the XVth Plenary Assembly,” CCIR Report 881, vol. 5, Geneva, 1982.

Dougherty, H. T., and E. J. Dutton: “The Role of Elevated Ducting for Radio Service and Inter-

ference Fields,” NTIA Report 81–69, March 1981.

Eckersley, T. L.: “Ultra-Short-Wave Refraction and Diffraction,” J. Inst. Elec. Engrs., pg. 286,

March 1937.

Epstein, J., and D. Peterson: “An Experimental Study of Wave Propagation at 850 Mc,” Proc.

IRE, pg. 595, May 1953.

Fink, D. G., (ed.): Television Engineering Handbook, McGraw-Hill, New York, N.Y., 1957.

Fink, D., and D. Christiansen (eds.): Electronics Engineer's Handbook, 3

rd

 ed., McGraw-Hill,

New York, N.Y., 1989.

Handbook of Physics, McGraw-Hill, New York, N.Y., 1958.

Harrison, Cecil: “Passive Filters,” in The Electronics Handbook, Jerry C. Whitaker (ed.), CRC

Press, Boca Raton, Fla., pp. 279–290, 1996.

Hauptstuek, Jim: “Interconnecting the Digital Chain,” NAB 1996 Broadcast Engineering Confer-

ence Proceedings, National Association of Broadcasters, Washington, D.C., pp. 360–358,
1996.

Heymans, Dennis: “Hot Switches and Combiners,” Broadcast Engineering, Overland Park,

Kan., December 1987.

Jordan, Edward C. (ed.): “Reference Data for Engineers—Radio, Electronics, Computer and

Communications, 7

th

 ed., Howard W. Sams, Indianapolis, Ind., 1985.

Judd, D. B., and G. Wyszecki: Color in Business, Science and Industry, 3rd ed., John Wiley and

Sons, New York, N.Y.

Kaufman, Ed: IES Illumination Handbook, Illumination Engineering Society.

Lapedes, D. N. (ed.): The McGraw-Hill Encyclopedia of Science & Technology, 2nd ed.,

McGraw-Hill, New York, N.Y.

Longley, A. G., and P. L. Rice: “Prediction of Tropospheric Radio Transmission over Irregular

Terrain—A Computer Method,” ESSA (Environmental Science Services Administration),
U.S. Dept. of Commerce, Report ERL (Environment Research Laboratories) 79-ITS 67,
July 1968.

McClanahan, M. E.: “Aural Broadcast Auxiliary Links,” in NAB Engineering Handbook, 8th ed.,

E. B. Cructhfield (ed.), National Association of Broadcasters, Washington, D.C, pp. 671–
678, 1992.

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Broadcast Transmission Systems