following: sideband power, error rate, and percentage
of interrogations answered.
Maximum Useable Frequency (MUF) Option
The maximum useable frequency option is a
routine that calculates the optimum frequency for
This routine calculates a
frequency for each hour of the day based on
geographic location, the range of other participants in
the net, and sunspot activity.
The multi-frequency link option improves current
by simultaneously using four
The normal configuration for multi-
frequency link operations uses three HF frequencies
and one UHF frequency. To implement this option,
three additional processor boards are installed in the
data terminal. Each data terminal board is connected
to a separate radio, as shown in figure 5-3.
Figure 5-3.Block diagram of the AN/USQ-125 data
terminal configured for multi-frequency link operations.
During the Link-11 receive cycle, each processor
demodulates the link signal and sends the data to the
master processor board.
The master processor
compares the received data and selects the signals
with the fewest errors to send to the CDS computer.
Although this mode is normally used with three HF
frequencies and one UHF frequency, there is no set
limitation of the radio configuration.
On-line and Off-line System Test Options
The data terminal provides several options for
both on-line and off-line testing. These include the
following: radio echo test, loopback tests 1,2,3, and
4, and DTS fault isolation tests. The radio echo test,
loopback test 1, and loopback test 4 are on-line tests,
while loopback test 2, loopback test 3, and the DTS
fault isolation tests are off-line tests.
RADIO ECHO TEST. When this option is
selected, the data terminal is placed in full-duplex
mode. This option is selected when a single station
POFA is run with the radio and checks the operation
of the computer interface, the crypto device, the data
terminal, and the radio.
LOOPBACK TEST 1. Loopback test 1 is
selected when running a single station POFA without
the radio. When you select this test option, the audio
lines are internally disconnected from the radio and
the audio outputs are connected to the audio inputs.
Full-duplex operation is also enabled. This test
checks the operation of the computer interface, the
crypto device, and the data terminal.
LOOPBACK TEST 2. Loopback test 2
configures the data terminal for an off-line self-test.
The audio lines are disconnected from the radio and
the audio output lines are internally jumpered to the
audio input lines.
A test message is internally
generated and sent through the audio circuits. The
receiver output is monitored for data errors, parity
errors, control code errors, and preamble recognition.
Any errors detected will cause the LOOPBACK FAIL
indicator to be displayed.
LOOPBACK TEST 3. Loopback test 3 is a
data terminal to radio test. Normal audio connections
are maintained, while the computer interface is
disabled. A test message is internally generated and
repeatedly sent through the radio. As with loopback
test 2, the receiver output is monitored for data errors,
parity errors, control code errors, and preamble
Any errors detected will cause the
LOOPBACK FAIL indicator to be displayed.