Figure 4-4. Rf Loopback - Comtech EF Data SDM-300L3 Installation And Operation Manual

SDM-300L3 Satellite Modem
Front Panel Operation
FUNCTION SELECT: CONFIGURATION: DEMODULATOR:
RF LOOP BACK
IMPORTANT
Programs the modem for RF loopback operation. When RF loopback is turned on, the
demodulator is programmed to the same frequency as the modulator. When RF loopback
is turned off, the demodulator is tuned to the previous frequency. Refer to (Figure 4-4)
for a block diagram of RF loopback 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
SATELLITE MODEM
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.
RF LOOP BACK
This is a Test Mode.
DATA
ENCODER/
INTERFACE MODULATOR
MICRO-
COMPUTER
DEMODULATOR/
DECODER

Figure 4-4. RF Loopback

OFF
TX = 1200 MHz
SUPPLY
POWER
RX = 1225 MHz
RF LBK = 1200 MHz
LOOPBACK CHANGES DEMOD
RECEIVE FREQUENCY TO
70 MHz WITHOUT LOSING
ORIGINAL PROGRAMMING
INFORMATION.
4–21
Revision 1
MN/SDM300L3.IOM
TRANSMIT RF
EQUIPMENT
ANTENNA
AC POWER
RECEIVE RF
EQUIPMENT