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SLM-7650 Satellite Modem
Operation
3.4.1.2
Demodulator Menu
Menu Item
RX-DR
Data Rate, Code Rate, and
Modulation Type
RX-IF FREQUENCY
DESCRAMBLER TYPE
DESCRAMBLER
DIFF. DECODER
IF LOOP BACK
(Test Mode Configuration)
BER THRESHOLD
Filter:
A, B, C, D, or V
Data rates are referenced in paragraph 3.3.
On entry, the current receiver rate is displayed with the flashing cursor on the first
character of the code rate on line 1. The data rate is displayed on line 2. Press an
arrow key to select one of four pre-defined rate (A, B, C, or D). To select the
currently defined variable data rate, select RX-V, and press [ENTER] twice.
To change the rate using the variable rate selection, press [ENTER] when RX-V is
displayed. A flashing cursor is displayed on the first character of the coding type
on line 1. Press [←] or [→] to move the flashing cursor, and [↑] or [↓] to increment
or decrement the digit at the flashing cursor. Press [ENTER] to execute the
change.
Programs the demodulator receive frequency between 50 and 90 MHz or 100 to
180 MHz, in 1.0 Hz steps.
On entry, the current receive frequency is displayed with the flashing cursor on
the first character. Press [←] or [→] to move the flashing cursor, and [↑] or [↓] to
increment or decrement the digit at the flashing cursor. Press [ENTER] to execute
the change.
Programs the descrambler IESS, OM73, or TURBO.
On entry, the current status of the synchronous descrambler is displayed. Press
an arrow key to make the selection. Press [ENTER] to execute the change.
Programs the descrambler On or Off.
On entry, the current status of the synchronous descrambler is displayed. Press
an arrow key to make the selection. Press [ENTER] to execute the change.
Programs the differential decoder on or off.
On entry, the current status of the differential decoder is displayed. Press an
arrow key to make the selection. Press [ENTER] to execute the change.
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 5-9 for a block diagram of IF loopback operation.
On entry, the current status of IF loopback is displayed. Press an arrow key to
make the selection. Press [ENTER] to execute the change.
Sets the BER threshold.
If the BER threshold set is exceeded, a receive fault will be indicated by the
modem status indicators. BER threshold may be set from 1.0 E-3 to 1.0 E-8, or
may be disabled by specifying None.
On entry, the current setting of the BER threshold is displayed. Press [↑] or [↓] to
select the desired setting. Press [ENTER] to execute the change.
3-10
Specifications/usage
Revision 4
MN/SLM7650.IOM
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