c. Frequency Range. The frequency range is 30 to
87.975 MHz channelized in tuning increments of 25 kHz.
In addition a frequency offset tuning capability of -10 kHz,
-5kHz, +1kHz is provided in both receive and transmit
mode; this frequency is not used in the ECCM mode.
Mode select switch HOM.
Operating frequency Set.
Any strong single channel signal within the
frequency range of the radio set can be used
FM button on HSI MODE SELECT PANEL
press. Check that SEL lamp is lit.
Homing procedures. The course deviation
bar on the HSI provides the primary navigation indication
when the set is in homing mode. The bar only provides
information on whether the helicopter is left, right, on
heading to a signal source, or over the signal source. The
TO-FROM ambiguity arrows will not function and selec-
tive source feature is not available. Ambiguity is solved
using either of the following methods:
Directional method. When the helicop-
ter is heading inbound to the signal source with the bar
centered, the indications are directional in that a change
in heading to the right will cause the bar to drift to the left.
Conversely, a change in heading to the left will cause the
bar to drift to the right. When the helicopter is heading
outbound from the signal source with the vertical pointer
centered, the indications are nondirectional in terms of
steering. A change in heading to the right will cause the
bar to drift to the right. A change in heading to the left will
cause the bar to drift to the left.
Build and fade method. If the signal
source is transmitting a 150-Hz tone-modulated signal
and the helicopter is inbound to the signal source, the
tone will increase in intensity. The tone will decrease in
intensity on an outbound heading.
Additional homing characteristics. The fol-
lowing additional characteristics may be observed when
homing. The glideslope deviation pointer will rise from
the horizontal mark when the aircraft is inbound (increas-
ing signal strength) to a transmitter. The pointer will fall
to the horizontal mark when outbound. The glidescope
failure and navigation failure warning flags will be in view
if there is inadequate homing signal strength. A dip in the
horizontal pointer may or may not occur when passing
over the station, depending on the signal source, helicop-
ter speed, and altitude.
3-2-17. Controls and Functions VHF/FM Radio
Primary power OFF. Memory
battery power ON.
RT and ECCM modules are
tested. Results; GOOD or
RT on with squelch.
RT with no squelch.
RT in RECEIVE mode. Used
as a radio relay link.
Keyboard loading of preset fre-
TRANSEC variable loading is
Not an operational position.
Used to clear the TRANSEC
All power removed. Used dur-
ing extended storage.
Homing antennas are active;
communication antenna is dis-
connected. Provides pilot
steering, station approach, and
signal strength indicators.
Single channel mode of opera-
tion. Operating frequency se-
lected by PRESET selector
Frequency hopping mode se-
lected. PRESET selector posi-
tions 1-6 select frequency hop-
ping net parameters.
position selects control station
as the time standard for com-
Used in a single mode to se-
lect any operating frequency in
25 kHz increments.