BEHAVIOR
Long and lanky, the CB antenna bends and sways as the pickup truck it’s attached to accelerates. It pulls radio from the electromagnetic atmosphere and sends back replies: “That’s a ten-four, good buddy.”
HABITAT
Long CB antennas are often mounted on a bumper to keep them low enough to fit into garages. Shorter CB antennas are mounted on the roof or on side mirrors of trucks.
HOW IT WORKS
In the United States, citizens band radio operates in the band of frequencies around 27 MHz. Within this band of frequencies 40 channels are designated for CB use. CB users can select any of the channels to use. One channel, 16, is reserved for meeting other users and agreeing which other (lower-traffic) channel to use for conversation.
The radio wave at 27 MHz is 11 meters long. To best capture that signal, the antenna needs to be either one half or one quarter of the wavelength. One half of 11 meters would be too long to use on cars and trucks, so the preferred antenna length is one quarter of 11 meters, or 2.7 meters. That is still quite tall, so the antenna is often mounted on the lowest spot possible—the bumper. To protect the car from being scratched by the antenna as it moves, the antenna is often outfitted with a tennis ball that can bounce against the car.
In many cases, the 2.7-meter antenna would still be too long, so a loading coil is inserted into a shortened antenna. The coil improves reception on shorter than quarter-length antenna. A loading coil can be located anywhere along the length of the antenna, but is often near its base.
© 2009 by Ed Sobey
All rights reserved
Published by Chicago Review Press, Incorporated
814 North Franklin Street
Chicago, Illinois 60610
ISBN: 978-1-55652-812-5
Printed in the United States of America
5 4 3 2 1
Library of Congress Cataloging-in-Publication Data
Sobey, Edwin J. C., 1948–
A field guide to automotive technology / Ed Sobey.
p. cm.
Includes index.
ISBN 978-1-55652-812-5
1. Automobiles—Popular works. 2. Mechanics—Popular works. I. Title.
TL146.5.S63 2008
629.2—dc22
2008046620
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