Comtech EF Data SDM-309B - Manual (Page 37)

Operation SDM-309B Satellite Modem
3–6 MN/U-SDM309B Rev. #
RXA Receiver rate selection. Select one of four predefined receiver
decoder/data rate combinations or a variable rate selection.
On entry the current receiver rate is displayed with the flashing
cursor on the first character of the code rate on line one. The data
rate is displayed on line two. Use the arrow keys to select one of four
predefined rates. Filters that are not present may display as “N/A”
(not assigned) and can not be programmed. If your modem is
equipped with the variable rate option you can also select TXV and
enter the desired data rate.
To change the rate using the variable rate selection, press the
“ENTER” key when “RXV” is displayed. A flashing cursor will be
displayed on the first character of the coding type on line one. Use
the right and left arrow keys to move the flashing cursor and the up
and down arrow keys to increment or decrement the digit at the
flashing cursor. Press the “ENTER” key to execute the change.
RX_freq Programs the demodulator receive frequency between 50 MHz and
90 MHz or 100 MHz and 180 MHz in 2.5 KHz Steps.
On entry the current receive frequency is displayed with the flashing
cursor on the first character. Use the right and left arrow keys to
move the flashing cursor and the up and down arrow keys to
increment or decrement the digit at the flashing cursor. Press the
“ENTER” key execute the change.
Note: The receiver frequency is programmable within the specified
range (50 - 90 MHz or 100 - 180 MHz ) in 2.5 KHz Steps.
DifDecdr Programs the differential decoder On or Off.
On entry the current status of the differential decoder is displayed
with the flashing cursor on the first character. Use the arrow keys to
select ON or OFF. Press the “ENTER” key to execute the change.
IFLoopBk *Programs the modem for IF loopback operation. When the IF loop-
back is turned on the demodulator input is connected to the
modulator output through an attenuator and 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 turned to it’s previous frequency and
is reconnected to the IF input. See Figure 3-8 for a block diagram of
IF loopback operation.
On entry the current status of the IF loopback is displayed with a
flashing cursor on the first character. Use the arrow keys to select
ON or OFF. Press the “ENTER” key to execute the change.
RFLoopBk *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 it’s previous frequency. See Figure 3-9 for a
block diagram of RF loopback operation.
On entry the current status of the RF Loopback is displayed with the
flashing cursor on the first character. Use the arrow keys to select
ON or OFF. Press the “ENTER” key to execute the change.