Modem Test Modes; If Loopback; Figure 5-9. If Loopback - Comtech EF Data SLM-7650 Installation And Operation Manual

SLM-7650 Satellite Modem
Maintenance
5.3.4

Modem Test Modes

The modem has built in capability to assist the operator in performance verification.
5.3.4.1

IF Loopback

When IF loopback is turned ON (Configuration-Demodulator menu), the demodulator
input is internally connected to a sampled output from the modulator. Also the
demodulator is programmed to the same IF frequency as the modulator. This test mode is
a quick way to verify the operation of the modem without the need to disconnect any
cables. When IF loopback is turned off, the demodulator is programmed back to the
previous frequency and is reconnected to the IF input.
NOTE: The data rate of the mod and demod must match for IF Loopback to operate
CUSTOMER
DATA
REMOTE SERIAL
INTERFACE
FAULT INDICATORS
SATELLITE MODEM
properly. The modulator channel is not affected by this test mode and will
continue to operate normally.
DATA
IBS, IDR or 308-2 ENCODER/
INTERFACE
MODULATOR
COMPUTER
DEMODULATOR/
DECODER

Figure 5-9. IF Loopback

MICRO-
POWER SUPPLY
5–19
Revision 4
MN/SLM7650.IOM
TRANSMIT RF
EQUIPMENT
ANTENNA
AC POWER
RECEIVE RF
EQUIPMENT