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RADIO COMMUNICATIONS
IN THE DIGITAL AGE
VOLUME TWO:
VHF/ UHF TECHNOLOGY

VHF/UHF Handbook in PDF Zipped

First Printing, June 2000
Copyright © 2000
By Harris Corporation
All rights reserved
Library of Congress Catalog Card Number: 00 132465
Harris Corporation, RF Communications Division
Radio Communications in the Digital Age
Volume Two: VHF/ UHF Technology
Printed in USA
6/ 00 RO 10K
B2008

© Harris Corporation

All Harris RF Communications products and systems included herein are trademarks of Harris Corporation.

With gratitude to Hal Herrick for his dedication and fortitude in writing this handbook.

TABLE OF CONTENTS

INTRODUCTION 1

CHAPTER 1 PRINCIPLES OF RADIO COMMUNICATIONS

CHAPTER 2 VHF/ UHF RADIO PROPAGATION

CHAPTER 3 ELEMENTS IN A VHF/ UHF RADIO SYSTEM

CHAPTER 4 NOISE AND INTERFERENCE

CHAPTER 5 DATA COMMUNICATION VIA VHF/ UHF RADIO

CHAPTER 6 UHF SATCOM

CHAPTER 7 SECURING COMMUNICATIONS

CHAPTER 8 SYSTEMS AND APPLICATIONS

CHAPTER 9 FUTURE DIRECTIONS

GLOSSARY

INTRODUCTION

This is Volume 2 of an introductory series on radio communications
Technology. This volume covers very high frequency (VHF), ultra high
frequency (UHF), and Satellite Communications (SATCOM) technologies,
as well as the modern digital coding and modulation capabilities that optimize information output and security.

The Communicatorís Tool Kit

A carpenter relies upon an assortment of chisels, drills, and hammers to
do the job. Each type of tool is suited for a particular task. Likewise, the modern communications system designer makes use of HF, VHF, UHF, and
SATCOM tools, and capitalizes on the unique capabilities that each brings
to meet the requirements. Summaries of the most prominent capabilities
of each radio frequency band are given below. Subsequent chapters will
describe them in more detail.

HF: Around the Corner to Around the World

Before SATCOM technology existed, HF radios were the only means of
communicating to ships at sea. The fact that HF can communicate beyond
the horizon makes it an indispensable tool for long distance ship- to- ship
and ship-to-shore messages. Likewise, before the days of the transatlantic
cables, HF (or short wave) radios were the only way to talk between
continents. Today they are still used to share the overall burdens of
long distance communications.

But the unique virtue of HF radio has also created some challenges.
Worldwide radio transmissions are easy to intercept and the HF spectrum
is complicated by signals emanating from the many individual transmitters
located around the world. Special techniques must be implemented in the
radios to take advantage of the radioís long range, while still preserving
the clarity of the channel and reduce interception.

Encryption reduces unfriendly utilization of intercepted signals and
sophisticated coding schemes helps fight through clutter, but these
techniques can reduce throughput (compared to that of a clear channel).
Nevertheless, HF radios still play an indispensable role in the communicatorís tool kit. HF manpack radios with various antenna options can cover a practical range of from ďaround the cornerĒ to ďaround the world.Ē
Although some long range communications are now transmitted via satellite, HF still has the advantage of not requiring (or relying on) any infrastructure.

VHF: Man to Man

The VHF band was an early choice for manpack radios used by ground troops to communicate within a local (five- mile or so) area. Antennas and selective- tuning components of VHF radios are very much smaller than their HF counterparts.

Advances in the semiconductor industry have also increased the efficiency
of VHF radios because batteries are smaller, lighter, and longer- lived than those required in the past.

Unlike HF, VHF transmissions lack the ability for ionospheric bounce and
are limited to line- of- sight (LOS) communication. This reduces radio emission clutter throughout an extended battlefield and limits the vulnerability to unfriendly interception.

The wider channel bandwidth capabilities of VHF radios increase the
efficiency of coding and encryption schemes and allow greater data
throughput than that of HF radios. Wider bandwidth and limited range make these radios ideal for squad- to- squad communications.

UHF: Ground to Air for Close Support

UHF tuning elements and antennas are even smaller than those of VHF and are much easier to mount on supersonic fighter aircraft, making UHF an ideal choice for ground- to- air communications. Like VHF radios, UHF radios share the advantages of being line of sight and having wide bandwidth. Modern military forces now prefer the UHF spectrum for ground-to-air communications.

SATCOM: Hails to (and from) the Chief

It is essential for front line units to communicate with the command centers that are sometimes hundreds, if not thousands, of miles away. With the advent of military satellites, SATCOM technology can complement HF equipment.

Although LOS is typically five miles or less along the ground between
manpack radios, the vertical LOS range of a UHF signal is tens of
thousands of miles. This enables UHF radios to reach orbiting military
satellites that are designed to retransmit the signal back to earth. The
retransmitted signal covers a huge footprint and is ideal for long range
communications.

The highly directional antennas pointed up at the sky that are used with
Tactical Satellite (TACSAT) radios, reduce ground radiation of front line
TACSAT traffic. This makes SATCOM traffic much more difficult to
intercept than that from HF radios.

Although it is true that the enemy can receive a downlink from a satellite,
encryption denies access to the data and the source of the emanations
gives no clue as to the location of either the source or the destination
of the data path.

The Multiband Radio

In this age of specialization a large, conventional military force has the
ability to carry an assortment of radios, each carefully designed for a
specific purpose. But the situation of a small Special Forces combat team
is very different. Although they need to have access to all of the available military communication channels, they canít afford the luxury (or the weight) of carrying the required multitude of radios. Hence, the
multiband radio.

Similarly, installation space constraints in vehicles, shelters, small boats, etc., are being addressed with multiband radios.

Just as the small multipurpose pocket tool that folds open to display a
knife, screw driver, pliers, and can opener can serve as an emergency tool
box, the multiband manpack radio is designed for the multipurpose needs
of Special Forces. Some multiband radios also provide a satellite link
allowing them to extend their range further.

Putting it all together

Subsequent chapters in this handbook develop the basic principles and
operating modes of the radios mentioned in this introduction. Operating
characteristics of each radio frequency band will be described and
compared with respect to performance and application.

But there is a lot more than frequency band that defines the performance
of a radio. The following pages also touch upon the world of exotic
waveforms that punch through noise, defy attempts at interception, and
provide data high data rates that previously were considered impossible.

Stay tuned!