Table 3A-2. Self-test Codes
No fault found
Frequency out of range
5 Vdc below limit
Forward power below limit
5 Vdc above limit
Transmitter temperature excessive
12 Vdc below limit
Tuning voltage out of limit at highest receive
12 Vdc above limit
Tuning voltage out of limit at 118 MHz
Synthesizer not locked
Local oscillator output below limit
No-signal AGC voltage too high
Inadequate AGC voltage increase with rf signal
BCD frequency code invalid
Reflected rf power above limit
2/5 frequency code invalid
Transmitter timed out
Serial message invalid
3A-11. HF COMMAND SET (718U-5).
a. Description. The HF command set provides
long-range voice communications within the frequency
range of 2.000 to 29.999 MHz. The HF command set
employs standard Amplitude Modulation (AM), Lower
Sideband (LSB) modulation, or Upper Sideband (USB)
modulation. The distance range of the HF command
set is approximately 2,500 miles, and varies with
atmospheric conditions. The HF command set is
protected by the 3-ampere HF RCVR and the
25-ampere HF PWR circuit breakers located on the
overhead circuit breaker panel, Figure 2-16, Sheets 1
and 2. The associated antenna is shown in Figure
Keying the HF radio set while operating the
ADF No. 2 set causes unreliable ADF
b. Controls and Functions, HF Command Set
Control Panel. Refer to Figure 3A-6.
frequency is selected by turning the frequency selector
controls until the desired operating frequency is
indicated. The controls may be operated in any order.
(2) MHz Indicators. Indicates operating
frequency of set.
(3) SQL Control. The squelch control is
adjusted to mute, undesired, background noise.
Setting the control too far counterclockwise can result
in blocking out weak signals. There are two different
configuration is the voice-operated squelch control that
functions to mute the receiver output in the absence of
a receive signal. The other type combines with RF
gain control. Adjustment method of the squelch
control is different for the two configurations.
(4) RF TEST Indicator. Four conditions of
the RF TEST lamp indicate the operational status of
the system. The mode selector must be in the RF
TEST mode position. Lamp illuminated or flashing
with system unkeyed provides a lamp test of the RF
TEST lamp. Lamp not illuminated, flashing, or
illuminated with the system keyed indicates the
operational status of the rest of the system.
(b) Blinking. Indicates fault in power
(c) Extinguished. System is operational.
(5) Mode Selector. Turns set off and
determines operating mode.
(a) OFF. Turns set off.
(b) USB. Places set in Upper Sideband