Table 3A-1. VHF Communications Transceiver Control UnitChannel/Frequency Scheme
(118.000 To 136.992 MHz Range)
Adjust the volume and perform a quick squelch
test by setting the power and mode switch on the
transceiver control unit to SQ OFF and adjusting the
volume level with background noise. After a
comfortable listening level has been established,
return the power and mode switch to the ON position.
All background noise should disappear unless a
station or aircraft is transmitting on the active
selection is made using either the frequency select
knobs, or the XF / MEM switch.
There is usually an installer supplied
8.33/25 kHz select switch in the cockpit.
This switch provides a convenience to the
pilots by not having to "ratchet pass" the
8.33 kHz channels when not operating in
8.33 airspace. The selected position of the
annunciated, depending on installation.
After the desired frequency is set into the preset
frequency display, it can be transferred to the active
frequency display by momentarily setting the XF /
MEM switch to XF. At the same time that the preset
frequency is transferred to the active display, the
previously active frequency is transferred to the preset
display. A short audio tone is applied to the audio
system to indicate that the active frequency has been
changed, and the ACT annunciator on the control will
flash while the transceiver is tuning to the new
The active annunciator's continuing to
flash indicates that the transceiver is not
tuned to the frequency displayed in the
The transceiver control unit's memory permits
storing up to six preset frequencies. Once stored,
these frequencies can be recalled to the preset display
by positioning the XF / MEM switch to the MEM
position. The storage location (CHAN 1 through
CHAN 6) for the recalled frequency is displayed in the
active frequency display while the XF / MEM switch is
held in the MEM position. All six stored frequencies
can be displayed one at a time in the preset display by
repeatedly positioning the XF / MEM switch to the
MEM position. After the desired stored frequency has
been recalled to the preset display, it can be
transferred to the active display by momentarily
positioning the XF / MEM switch to the XF position.
During normal operation, all frequency selections
and revisions are done in the preset frequency display.
However, the active frequency can be selected directly
as described in the following paragraph.