Figure 3-17. ADF Control Panel (DF-203)
relative to a selected ground radio station. It may also be
used to home to a selected station, find aircraft position, or
transmissions. The system is designed to provide reliable
reception of a 400-watt radio station at a range of 65 nautical
miles throughout a 360degree turn of the aircraft. It operates
in a frequency range of 190 to 1750 kilohertz. Bearing
indications are displayed visually on the RMI's and aural
signals are applied to the audio control panels. The ADF
systems consists of a receiver, located on the forward side of
the aft cabin bulkhead inside the pressure vessel; a control
unit, located on the pedestal extension; a nondirectional sense
antenna, installed in the aircraft dorsal fin; a directional loop
antenna, located on the underside of the fuselage; and a
quadrangle error corrector, installed on the loop antenna (to
compensate for the deflection of arriving radio signals by the
wings and fuselage of the aircraft). The system is protected by
a 1-ampere ADF, a 5-ampere RADIO RELAY, and a 35-
ampere AVIONICS BUS FEEDER No.2 circuit breaker
located on the overhead circuit breaker panel (fig. 2-27).
Keying the HF radio set while
operating the ADF radio set will cause
a momentarily unreliable ADF signal.
Controls and Functions (ADF Control Panel, fig. 3-
L-LOOP-R control. Operative only when the
function switch is in the LOOP or ADF position. Center
position removes rotation signals from the loop antenna and
the ADF pointer on the RMI's. L (left) or R (right) of center
applies rotation signals to loop antenna and ADF pointer on
RMI's for 360-degree rotation left or right. Center position
holds antenna position.
BFO-OFF. At BFO (on) setting, permits fine
tuning with Beat Frequency Oscillator (BFO). Also provides
audio tone when receiving unmodulated CW. OFF position
turns BFO off.
Tuning meter. Indicates relative strength of
TUNE control. Selects operating frequency.
Range switch. Selects operating frequency
FREQUENCY indicator. Indicates selected
Mode selector. Selects operating mode.
OFF. Turns set off.