MUCH OF YOUR CAR’S TECHNOLOGY is hidden beneath the metal and plastic body or hood. But some equipment cannot be hidden or protected inside the car. In some cases designers blend the machines into the car’s body so you don’t notice them. Others are themselves design elements and some pop out from hidden recesses when needed.
Antenna, AM/FM
BEHAVIOR
It wiggles in the wind as you drive at highway speeds, showing patterns of standing waves. It also receives the radio signals that bring you news, sports, music, and way too many commercials. As if that weren’t enough, it also provides a perch for
antenna balls.
HABITAT
On most cars it is the stiff wire that rises vertically from just in front of the windshield on the passenger’s side or on the rear fender on the driver’s side.
HOW IT WORKS
Antennas are tuned to receive electromagnetic radiation within certain frequency bands. Note their similarity to tiny antenna on old cell phones. (Newer cell phones,
operating at even higher frequencies, have smaller antenna that fit inside the hand unit.) AM and FM radio stations broadcast at low frequencies and large antennas are needed to receive those signals at these frequencies.
To transmit an AM signal the ideal antenna is huge. Hence, AM radio stations have very tall towers and long antenna. FM stations, which operate at higher requencies, need shorter transmit antennas. But both types of stations have transmit antennas many times larger than the antenna on your car. Driving around with a 100-foot-tall antenna just won’t work, so the transmitted signals are strong enough that the less
than optimum height antenna on your car still receives radio signals.
INTERESTING FACTS
Radio antennas had been mounted in the cloth roofs of cars until the advent of steel roofs for cars in 1934. The new roofs reflected and blocked radio waves, so engineers experimented with placing antenna elsewhere, eventually settling on the favored location behind the hood.
© 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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