TM 55-1510-220-MTF
PROCEDURE
TROUBLESHOOTING
REFERENCE
F.
AVIONICS FLIGHT CHECKS (CONT)
d.
Establish communications with a ground station at least 150 miles distant on at least three
frequencies (one each from the lower, middle, and upper frequency ranges). Establish two-way
communications on AM and, when possible, on USB. Obtain signal quality reports from the other
station and note received signal quality.
NOTE
The intelligibility of SSB voice operations becomes degraded
when the receiver and transmitter differ in frequency by a
small amount (approximately 50 Hz). The voice pitch will
sound either too high or too low. The cause may be either the
receiver or transmitter.
e.
Frequency accuracy - Check as follows:
(1) Station WWV - Select the frequency that provides the best signal. The station broadcasts on
2. 5000, 5.0000, 15.0000, 20.0000, and 25.0000 MHz. The higher the frequency selected, the
more accurate the frequency check will be.
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