Comtech EF Data SDM-9000 - Manual (Page 85)

SDM-9000 Satellite Modem Operation
Rev. 4 4–11
4.2.1.2 Configuration Demodulator
RX X CODE_RATE RX rate selection. Select one of four (A, B, C, or D) pre-defined
RX decoder/data rate combinations.
On entry, the current RX rate is displayed on line 1. The data
rate is displayed on line 2. Press [
←
] or [
→
] to select one of
four pre-defined rates (A, B, C, or D).
RX-IF FREQUENCY Programs the demodulator RX frequency between 50 and 180
MHz, in 2.5 kHz steps.
On entry, the current RX frequency is displayed with the
flashing cursor on the first character. Press [
←
] or [
→
] to move
the flashing cursor. Press [
↑
] or [
↓
] to increment or decrement
the digit at the flashing cursor. Press [ENTER] to execute the
change.
DIFF. DECODER Programs the differential decoder on or off.
On entry, the current status of the differential decoder is
displayed. Press [
←
] or [
→
] to select ON or OFF. Press
[ENTER] to execute the change.
RF LOOP BACK
(Test Mode Configuration
Option) 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 4-17 for a block diagram of RF loopback
operation.
Note: RF loopback nullifies IF loopback.
On entry, the current status of the RF loopback is displayed.
Press [
←
] or [
→
] to select ON or OFF. Press [ENTER] to
execute the change.
IF LOOP BACK
(Test Mode Configuration
Option) 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. The
demodulator is programmed to the same frequency as the
modulator. An attenuator within the modem connects the IF out
to the IF in. When IF loopback is turned off, the demodulator is
tuned to the previous frequency and is reconnected to the IF
input. Refer to Figure 4-18 for a block diagram of IF loopback
operation.
Note: IF loopback nullifies RF loopback.
On entry, the current status of IF loopback is displayed. Press
[
←
] or [
→
] to select ON or OFF. Press [ENTER] to execute the
change.