as appropriate. The antenna snaps into an upright
position. Fully extend all five telescopic sections
of the half-wave antenna by grasping it by its tip
and pulling outward.
2. Set the function switch to the mode of
operation that you want. The function switch is
set by rotating the thumb knob on the right-hand
side so that the arrow points to the mode selected.
The function switch is detented and clicks into
each position. Rotate the knob down one click
(from OFF) for VOICE/MCW 243.0 operation,
or two clicks for BCN 243.0 operation. For
VOICE 282.8 operation (secondary channel),
push the button with the arrow and rotate the
function switch knob up one click.
3. For voice operation, hold the radio set and
adjust the VOL control. To transmit, push down
the PRESS TO TALK button and speak directly
into the TALK microphone.
4. If guard channel steady-tone transmission
or Morse code operation is desired, set the
function switch to VOICE/MCW 243.0. Depress
the MCW button to transmit the tone. Listen for
the sidetone in the LISTEN speaker or earphone
while the MCW button is depressed. This sidetone
indicates proper transmitter operation.
5. For guard channel beacon operation, set
the function switch to BCN 243.0. The transmitter
239.439
Figure 5-9.—Beacon set, radio, AN/URT-33A (front view).
continuously sends the swept-tone beacon signal
at this setting. Listen for the sidetone as an
indication of proper operation. In the beacon
mode, the sidetone is a chirping sound.
NOTE: Since the transmitter is keyed
automatically in the beacon mode, and
since continuous transmission may be
needed for a prolonged period of time, the
AN/PRC-90 may be placed upright on a
flat surface. It will then transmit
automatically.
AN/URT-33A BEACON SET RADIO
The Beacon Set Radio, AN/URT-33A (figs.
5-9 and 5-10), is an emergency radio beacon
transmitter that, when properly actuated,
transmits a tone-modulated radio frequency signal
on the emergency guard frequency of 243.0 MHz.
Although the AN/URT-33A was designed to
be placed into a parachute pack, the Navy
normally places the beacon radio into the seat pan
(RSSK) or life rafts. Instructions for properly
rigging the AN/URT-33A can be found in
NAVAIR 13-1-6.1.
The AN/URT-33 radio has two types of
antennae. One type is the flexible wire antenna.
This antenna is used during parachute descent
239.440
Figure 5-10.—Beacon set, radio, AN/URT-33A (rear view).
5-10
