indicators in the following text. Each number
corresponds to a pointer in figure 1-8.
1. Preset channel selector switch–Selects anyone
of 20 preset channels.
2. CHAN indicator–Indicates channel selected by
the preset channel selector.
3. SET switch–Sets anyone of the available 7000
normal mode frequencies.
4. MEMORY read display–Displays the fre-
quency that has been selected by preset channel selector.
5. Memory READ switch–Allows selected fre-
quency to be displayed.
6. Manual frequency selector switch–Selects
hundredth and thousandth’s digit of the desired manual
frequency in steps of 25 (00, 25, 50, or 75).
7. Manual frequency selector switch–Selects the
tenth’s digit of desired manual frequency (0 through 9).
8. Manual frequency selector switch–Selects
unit’s digit of the desired manual frequency (0 through
9).
9. Manual frequency selector switch–Selects
ten’s digit of the desired manual frequency (0 through
9).
10. Manual frequency selector switch–Selects
hundred’s digit of the desired manual frequency (either
2 or 3). In the A position, the radio set in an anti-
jamming mode. In the T position, the radio set is enabled
for transmission and reception for one minute.
11. Function selector switch–Selects operating
modes.
a. OFF–Shuts down the radio set.
b. T/R–Enables main receiver and transmitter.
c. T/R+G–Enables main receiver, transmitter,
and guard receiver.
d. ADF–Sets the receiver transmitter to the AM
mode for automatic direction finding
operations.
e. SATCOM–Allows Satellite Communications
by setting the receiver transmitter to the
SATCOM mode.
12. FAULT status indicator–Steady illumination
indicates an RT fault, a slow flash (1/sec) indicates an
interface fault, and a fast flash (4/sec) indicates a control
box fault.
13. TONE switch–Enables transmission of an
audible tone on the selected frequency.
14. SONOBUOY COMMAND/MANUAL/
PRESET/GUARD–This switch selects the mode of
frequency selection.
a.
b.
c.
d.
SONOBUOY COMMAND–This position
causes the radio set control to deliver a serial
data stream corresponding to a preset
frequency in the controls memory.
MANUAL–In this position the frequency is
manually selected using the five manual
frequency selector switches.
PRESET–The frequency is selected using
the preset channel selector switch. This
position is also used for programming the 20
preset channels.
GUARD–This automatically tunes the main
receiver and transmitter to the guard
frequency and disables the guard receiver.
15. SQUELCH ON-OFF switch–Enables and
disables the squelch circuits of the main receiver.
UHF-2 Antenna Select Panel
The UHF-2 antenna select panel (fig. 1-9) selects
which antenna the UHF-2 radio set will use during
operation. There is one two-position switchlight on this
panel. The switchlight is marked UP ANT and LOW
ANT. When the upper tailcap antenna is selected, the UP
ANT portion of the switchlight will be illuminated
amber. When the lower antenna is selected, the LOW
ANT portion will be amber.
UHF MODES OF OPERATION
Figure 1-10 shows a simplified block diagram of the
UHF system.
The UHF-1 radio set provides the following modes
of operation: plain voice, cipher voice, ADF navigation,
plain voice guard, cipher voice guard, and secure
SATCOM. The UHF-2 radio set provides plain voice,
cipher voice, sonobuoy command, wide-band audio,
plain voice guard, cipher voice guard, link 11 plain data,
link 11 cipher data, TTY plain data, TTY cipher data,
and IACS data.
Operation of these radio sets is supported by various
equipment on board the aircraft. Mode selection for
UHF-1 is accomplished by the control box and the A344
voice selector. Mode selection for UHF-2 is
1-14
