radio waves travel much faster than sound waves.
Radio waves travel about 330 yards in a millionth of a
second. Therefore, the times involved in radar ranging
are much shorter than for sound ranging.
APPLICATIONS OF RADAR
Radar was originally devised as an instrument to
detect approaching ships or aircraft. Practice and
experience in reading the scope soon showed that radar
could do much more. By plotting successive positions
of enemy ships and aircraft, you could determine their
course and speed. Further experience made it possible
to determine whether the target was a battleship,
destroyer, aircraft, or a group of targets. Also, an
aircraft's altitude could be determined.
Use in Tactical Air Control
Both airborne and shipboard radar is a major link in
an operational system. It directs fighter aircraft to a
favorable position for intercepting enemy aircraft. The
air control officer can determine the number of fighters
so they can successfully attack and destroy the enemy.
Airborne early warning (AEW) aircraft, equipped
with high-powered radars, are used in tactical air
control. These aircraft extend the range of air control
radar by operating in areas outside the range of the
Electronics Technician (AT) rating maintains AEW
Use in Fire Control
The highly directional characteristics of radar
make it suited for directing fire control systems.
Focusing the radar energy into a narrow beam enables it
to display target position with a high degree of
accuracy. At the same time, it also displays target range.
The primary purpose of fire control radar is to
determine the correct position and attitude the aircraft
should be in to hit the specified target. Radar, in its early
stages of development, was useful as an aid to the
human eye under poor visibility conditions. It also
provided a more accurate and faster means of range
measurement. Presently, it provides a faster and more
accurate method of directing fire control than is
humanly possible. This feature is extremely important
considering the high speeds of today's aircraft and
missiles. The time available to launch an intercept
weapon effectively is measured in fractions of a second.
IDENTIFICATION FRIEND OR FOE (IFF)
The problem of distinguishing friend from foe in
warfare has increased because of the increased speed of
aircraft and ships. Radar can detect both sea and air
targets at long range. However, it displays both friend
and enemy similarly on the scope. It is not practical to
wait until the target has been visually identified to begin
preparing for battle.
A method other than visual recognition must be
used for early identification of the target. IFF is an
electronic system that allows a friendly craft to identify
itself automatically before approaching near enough to
threaten the security of other naval units.
A transponder in the friendly aircraft receives a
radio-wave challenge (interrogation). The transponder
transmits a response to a proper challenge, as shown in
figure 7-24. Upon receiving the proper challenge, the
transponder automatically transmits a coded reply,
which tells the challenger that a friend has been
challenged. The transponder stays in a standby
condition and transmits only when the proper challenge
is received. The challenger's receiver accepts the reply
of the challenged target and presents the replies on an
All operational aircraft and ships of the armed
forces carry transponders to give their identity when
challenged. For operations involving only friendly
MODE 1, 2 OR 3/A
MODE 1, 2 OR 3/A
Figure 7-24.Typical surface radar PPI composite display
showing several IFF responses.