TM 1-1520-238-10
Change 3
3-31
Table 3-9.
AN/ARN-89 Control Functions – continued
Control
Function
ANT AM
Provides for operation as an receiver using the sense antenna.
LOOP
Provides for receiver operation as a manual direction finder using only the loop antenna.
LOOP L-R control
knob
Manually provides for left and right control of the loop when the mode selector switch is in the
LOOP position. This control knob is spring-loaded to return to center.
AUDIO
Adjusts audio volume for station identification.
KILOHERTZ tune
controls
100 KHz coarse
tune control knob
Tunes receiver in 100 KHz steps as indicated by first two digits of the KILOCYCLES
indicator.
10 KHz fine tune
control knob
Tunes receiver in 10 KHz steps as indicated by last two digits of KILOCYCLES indicator.
CW, VOICE, TEST
switch
CW (in the COMP
mode)
Enables the tone oscillator to provide an audible tone for tuning to a (CW) station when the
mode selector switch is at COMP.
CW (ANT or
LOOP mode)
Enables the beat frequency oscillator to permit tuning to a CW station when the mode
selector switch is at ANT or LOOP.
VOICE
Permits (LF) receiver to operate as a receiver when the mode selector switch is at any
position.
TEST (in the
COMP mode)
Provides for slewing of the loop through 180 degrees to check operation of the receiver in the
COMP mode. This switch position is inoperative in LOOP and ANT modes.
TUNE meter
Indicates relative signal strength while tuning the set to a specific radio signal.
KILOCYCLES
indicator
Indicates operating frequency to which receiver is tuned.
3.12.3 Operating Procedures.
a. Starting Procedure.
1. Mode selector switch – COMP, ANT or LOOP.
2. Frequency – Select.
3. CW-VOICE-TEST switch – CW or VOICE as de-
sired.
4. CSC panel NAV A receiver select switch – ON.
5. Fine tune control – Adjust for maximum upward
indication on the TUNE meter.
6. AUDIO control – Adjust as desired.
b. COMP Mode Operation.
1. Mode selector switch – COMP.
The horizontal situation indicator No. 2 bearing
pointer and the radio magnetic indicator bearing
pointer will display the magnetic bearing to the
ground station from the helicopter as read
against the integral compass card on each in-
strument.
