and position fixing. The set also has a Beat
Frequency Oscillator (BFO) function, used to more
accurately tune weak signals. Reception distance of
reliable signals depends on the power output of the
transmitting station and the atmospheric conditions.
Bearing indications are displayed visually on the RMIs
and aural signals are applied to the audio control
panels. The ADF radio sets are protected by a
1-ampere circuit breaker, placarded ADF, located on
the overhead circuit breaker panel, Figure 2-16,
Sheets 1 and 2.
Keying the HF radio set while operating the
ADF No. 2 set will cause a momentarily
unreliable ADF signal.
b. Associated Controls and Functions. Refer
to Figure 3A-1.
(1) ICS # 1 ADF 1 / 2 Switch. Applies ADF
audio to respective headsets.
(2) FILTER V / OFF Switch. Selects whether
or not voice filter will be used with ADF audio.
(3) FILTER R / OFF Switch. Selects whether
or not range filter will be used with ADF audio.
(4) CABIN ADF-1 / OFF / ADF-2 Switch.
Selects desired ADF audio for use with cabin
c. Controls and Functions. Refer to Figure
(1) LOOP Control. Operative only when the
mode selector 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. First
position left (L) or right (R) of center applies slow
speed rotation signals to loop antenna and ADF
pointer on RMI's for 360° rotation left or right. Second
position left (L) or right (R) of center applies fast-speed
rotation signals to loop antenna and ADF pointer on
RMI's for 360° rotation left or right.
(2) BFO / OFF Switch. Turns BFO on or off.
(3) Tuning Meter. Indicates relative strength
of received signals.
(4) TUNE Control. Tunes receiver.
1. LOOP Control
2. BFO/OFF Switch
3. Tuning Meter
4. TUNE Control
5. Range Switch
6. FREQUENCY Indicator
7. Mode Selector
8. GAIN Control
Figure 3A-15. ADF Control Panel
(6) FREQUENCY Indicator. Indicates the
(7) Mode Selector. Determines operating
(a) OFF. Turns set off.
(b) ADF. Allows homing or automatic
direction finding operation.
(c) ANT. Allows reception using sense
(d) LOOP. Allows aural-null homing and
manual direction-finding operations.
(1) Automatic Direction Finder.
1. Mode selector ADF.
2. BFO / OFF switch BFO.
3. Range switch Select.