2. Test the ADF as follows:
a. CW-VOICE-TEST switch Set to TEST
position. Check that both bearing pointers
associated with the ADF rotate approxi-
b. CW-VOICE-TEST switch Release.
c. ANT Mode Operation.
1. Mode selector switch ANT
2. Monitor receiver in headset.
d. LOOP Mode Operation (manual direction find-
1. Mode Selector switch LOOP.
2. Turn the LOOP L-R control to L (left) or R (right)
to obtain an audio null and a TUNE indicator
null. Check either ADF bearing pointer for a dis-
play of magnetic bearing to or from the station.
The two null positions may be as much as 180
apart in this mode.
During an electrical system malfunction and
operating on EMERG BATT power, the HSI/
RMI will not provide adequate indications to
3.13 AUTOMATIC DIRECTION FINDER SET
ADF set AN/ARN-149 is an airborne, LF, ADF radio that
provides an automatic compass bearing on any radio sig-
nal within the frequency range of 100 to 2199.5 kHz. The
ADF displays helicopter bearing relative to a selected ra-
dio transmission. On the pilot instrument panel, it is shown
by the horizontal situation indicator (HSI) No. 2 bearing
pointer (fig 2-9). On the CPG panel, it is shown on the RMI
bearing pointer (fig 2-10). The ADF operates in the ANT
(audio only) and ADF modes. It also has a self test mode.
In addition, a submode provides the capability of identify-
ing keyed CW signals. The ADF receives 28 VDC from the
emergency DC bus through the ADF circuit breaker on the
pilot overhead circuit breaker panel. The HARS AC circuit
breaker on the pilot overhead circuit breaker panel pro-
vides power for the 26 VAC reference voltage used by the
3.13.1 Antenna. The ADF antenna (fig 3-1) is located on
the bottom center of the fuselage under the Doppler/Ra-
dar Altimeter (DRA) fairing.
3.13.2 Controls and Functions.
Controls for the AN/
ARN-149 are on the front panel of the ADF control panel
(fig 3-9) located on the pilot right console. The function of
each control is described in table 3-10.
AN/ARN-149(V)3 ADF Control Panel