Figure 4-4. Rf Loopback; If Loop Back - Comtech EF Data SNM-1001L Installation And Operation Manual

SNM-1001L Satellite Modem
Front Panel Operation
Note: RF loopback nullifies IF loopback.
Upon entry, the current status of the RF loopback is displayed. Press [↑] or [↓] to make the
selection. Press [ENTER] to execute the change.
CUSTOMER
DATA
REMOTE SERIAL
INTERFACE
FAULT INDICATORS
Note: When RF loopback is turned on, the demodulator receive frequency is programmed to be the same frequency as the modulator transmit
frequency. This test mode will verify the satellite link without changing the programmed frequency of the demodulator. When RF loopback is
turned off, the demodulator is programmed back to the previous frequency.
FUNCTION SELECT: CONFIGURATION: DEMODULATOR:

IF LOOP BACK

IMPORTANT
Programs the modem for IF loopback operation. When IF loopback is turned on, the demodulator
input is connected to the modulator output through an internal attenuator and the modulator
continues to TX a signal. The demodulator is programmed to the same frequency as the
modulator. When IF loopback is turned off, the demodulator is tuned to the previous frequency
and is reconnected to the IF input. Refer to Figure 4-5 for a block diagram of IF loopback
operation.
DATA
ENCODER/
INTERFACE MODULATOR
COMPUTER
DEMODULATOR/
DECODER
SATELLITE MODEM

Figure 4-4. RF Loopback

IF LOOP BACK
This is a Test Mode.
TX = 1200 MHz
MICRO-
POWER SUPPLY
RX = 1225 MHz
RF LBK = 1200 MHz
LOOPBACK CHANGES DEMOD
RECEIVE FREQUENCY TO
70 MHz WITHOUT LOSING
ORIGINAL PROGRAMMING
INFORMATION.
OFF
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Revision 1
MN/SNM1001L.IOM
TRANSMIT RF
EQUIPMENT
ANTENNA
AC POWER
RECEIVE RF
EQUIPMENT