January-February - Air Defense Artillery

4
Figure I. Block diagram of radar system.
on the North Sea approaches. Soon after the outbreak of
war additional radar stations were established and the "invisible
bastion" was complete. By 1940 radar art was sufficiently
advanced to give British pilots a three-dimensional
location of the enemy-range, azimuth, elevation-and an
estimate of numbers. An equipment for detection of aircraft
from night fighters was simultaneously developed.
This gave the Royal Air Force all the essential data to enable
them to win the Battle of Britain against the great
numerical odds of the Luftwaffe and to deserve Churchill's:
";'\fever have so many owed so much to so few."
The efforts of American and British laboratories were
combined in 1940. 1\ 1utual disclosures were made of British
and American accomplishments in radar up to that
time. The best civilian brains were enlisted in the quest
for better equipment through the National Defense Research
Committee, later part of the OfIlce of Scientific
Research and Development. By the time of the Japanese
attack on Pearl Harbor the Navv had alreadv installed on
key ships not only radar for aircr;ft warning, but also radar
for surface search and fire control, while the Armv had in
the field numbers of long-range aircraft warning sets, as
well as antiaircraft and searchlight batteries equipped with
radar.
Toda) Army and Aavy radar requirements are coordinated
to the point where many sets and nearly all component
parts are made interchangeable between the services.
The original Signal Corps and Aavy nomenclature has been
superseded for new equipment by a joint "A:'\" (Army-
:\'avy) system in which all sets or components developed
for either service are given the same nomenclature in the
supply catalog of both.
From our enemies, no new principle or radio device has
emerged, and for the most part, both Germany and Japan
have been content to follow industriously in the footsteps
?f the A.llies, lite~ally "pick~ng up". \-"hat inevitably has come
THE COAST ARTILLERY JOURNAL
of radar over Germanv is attributed to the fact that
scientists concentrated on other projects from 1
1944. Ho\\ ever, b) \'-E Day the importance of r
been realized by the Germans and the\ were rapi
taking us in this field.
THEOR 'I OF RADAR
i\lassachusetts Institute of Technology, one of th
in the field of radar, offers this definition of radar.
may be defined as the art of determining by radio e
presence of objects, determining their direction an
recognizing thelr character, and employing the d
obtained in the performance of military or naval a
The official U. S. derivation of the word "Radar
it means RAdio Detection And Ranging.
A radar set accomplishes the detection of targets
ing out pulses of ultra-high-frequency radio wave
from a high-power transmitter. These pulses are
trated into a beam (similar to a searchlight beam)
rectional antenna. \\Then the transmitted energy s
object, a portion of it is reRected in much the same
as the sound waves echo from the face of a cli
echo energy is detected by the receiver through its
and is translated into usable information on indicato
fact that radio waves travel at the constant velocity
enables us to determine the range, and the fact t
receiver antenna is directional enables the determin
azimuth and elevation.
Compoue1lts.
\Vhile there are many different types of radar sets,
mentally they all consist of six essential component 1
ure I).
1. Tra11Sill itter- Transmits the ultra-high freque
short, powerful pulses.
NOTE: In any discussion of radar considerable mention is mad
l'uPllcies and wave lengths. Often the two are used interchanJ:
delinite relation exists between the two, which may be expresse
inrmula:
f = 300 where f = frequency in cycles per second and X (
~ - = wave length in meters.