Comtech EF Data SDM-100A - Manual (Page 112)

Operation SDM-100A Satellite Modem
3–78 Rev. 0
TRANSMIT RF
EQUIPMENT
CUSTOMER
DATA
INTERFACE ENCODER/
MODULATOR
ANTENNA
AC POWER
POWER
SUPPLY
MICRO-
COMPUTER
REMOTE
SERIAL
INTERFACE
FAULT
INDICATORS
RECEIVE RF
EQUIPMENT DEMODULATOR/
DECODER
SATELLITE
SDM-100A
DATA MODEM
Figure 3-27. IF Loopback
Note: When IF loopback is turned on, the demodulator is looped back to the modulator inside the modem, and the
demodulator is programmed to the same frequency as the modulator. This test mode will verify the operation of the
modem. When IF loopback is turned off, the demodulator is programmed back to its previous frequency, and is
reconnected to the IF input.
TRANSMIT RF
EQUIPMENT
CUSTOMER
DATA
INTERFACE
ENCODER/
MODULATOR
ANTENNA
AC POWER
POW ER
SUPPLY
MICRO-
COMPUTER
REMOTE
SERIAL
INTERFACE
FAULT
INDICATORS
RECEIVE RF
EQUIPMENT DEMODULATOR/
DECODER
SATELLITE
SDM-100A
DATA MODEM
Figure 3-28. Baseband Loopback
Note: When baseband loopback is turned on, the data signal is looped back on the customer side of the interface.
This test mode will verify customer equipment, as well as cabling between the modem and the customer equipment.