When storing a frequency, the second
actuation of the STO switch must be done
within 5 seconds after selecting the channel
number or the first actuation of the STO
switch. If more than 5 seconds elapse, the
control will revert to the normal modes of
operation and the second store command
After a frequency has been stored in memory, it
will remain there until changed by using the STO switch.
Memory is retained even when the unit is turned off for
an extended period of time.
Power and mode switch - ANT,
ADF, or TONE (BFO).
ANT function - Position power and
mode switch to ANT. Select ADF
on audio system and adjust volume.
ADF function - Position power and
mode switch to ADF. Bearing
pointer will indicate relative bearing
to tuned station.
When the ADF system is not receiving a
reliable signal, bearing pointer will be
removed from view. The ADF bearing
station crossings because of signal loss.
TONE function - Position power and
mode switch to TONE (BFO). A
1000-Hz tone will identify keyed CW
Power and mode switch - ADF.
Tuning knobs - Tune a nearby NDB,
TEST switch - Depress. Bearing
pointer will rotate 90 degrees from
Release TEST switch and verify that
previous valid indication.
If the signal received is weak or of poor
quality, bearing pointer rotation will be slow.
ADF receiver fault codes are listed in table 3-8.
3-26. TACAN/DME SYSTEM (AN/ARN-154).
Description. The TACAN/DME system (fig.
3-26) operates in conjunction with TACAN and
groundspeed, time to station, and bearing to station.
elapsed time to distance by measuring the length of time
between the transmission of a radio signal to a selected
DME/TACAN station and the reception of the reply
signal. The distance is measured on a slant from the
aircraft to the ground station and is commonly referred to
as slant-range distance. Slant range approximates
actual ground distance. The difference between slant-
range distance and ground distance is smallest at low
altitude and long range, and greatest when in close
proximity to the selected ground station. The system is
capable of tracking the range of up to four stations and
the bearing of two stations simultaneously. The system
will operate on any one of 252 preselected frequencies
(126 X mode and 126 Y mode channels). Course
deviation, bearing to station, and distance to TACAN or
VORTAC stations are displayed on the EHSI. Distance,
time to station, bearing,
Table 3-8. ADF Receiver Fault Codes
RAM test failed (test failed at power-up)
No serial sync block received
No serial data block received for more than 2 seconds
Transponder label received in first block
I/O port 1 failure
I/O port 2 failure
Illegal ADF frequency
Serial input failed or stuck low
ADF not lock in ADF mode