RADAR service due to equipment limitations. The special circuits listed in Table 5-6 are
used to overcome equipment limitations.
Not an adjustable circuit. Keeps the RADAR transmitter and receiver
tuned to the same frequency. Adjusts for the effects of frequency
drift. Without AFC, many echo signals are lost.
FTC offsets the effects of heavy precipitation that tends to block
aircraft targets. Displays only the leading edge of long-duration
returns (precipitation) and allows small-target echoes to get through
Assures that targets appear with equal intensity, regardless of range
variation. It also prevents blooming of targets nearer the antenna. At
effect, STC makes the gain quite low to reduce the effects of the
Distinguishes between moving and stationary targets and blocks out
the stationary targets. Disadvantage to MTI is blind speed (target
disappearing at a certain speed); PRF eliminates blind speeds below
approximately twice the speed of sound. The figure shows a 20-mile
PPI display with MTI adjusted to 10 miles.
Automatically switches the RADAR system from MTI to normal and
from normal to MTI for the best presentation.
Table 5-6 -- Special circuits