Comtech EF Data CDM-425, Installation And Operation Manual

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CDM-425 Advanced Satellite Modem
Revision 0
Front Panel Operation 6–12 MN-CDM-425
6.2.1.3 CONFIG: Tx
Tx-IF Freq Power FEC Mod Data Scrambler
(Data 00192.000kbps, 00131.657ksps) (

)
On the top line – Use the
◄ ►
arrow keys to select a parameter. Press ENTER .
On the bottom line – Read-only Data and Symbol rate information is provided.
When Sub-Mux is ON, Composite Rate information replaces the Data Rate
information on the bottom line of this display.
6.2.1.3.1 CONFIG: Tx

Tx-IF
Tx: Carrier=On (Off,On,RTI) POCO=Off
SpectrumInvert=Off Tx
α=.35(.05-.35)(

)
Use the
◄ ►
arrow keys to select a parameter. Press ENTER .
Carrier – Use the
▲▼ arrow keys to select a parameter. Press
ENTER .
USE THE RTI FEATURE WITH EXTREME CARE! RTI (RECEIVE/TRANSMIT
INHIBIT), when selected, prevents transmission of the Tx carrier until the
demodulator is locked. To avoid shutdown of the Tx Carrier when the
demodulator loses lock for a very short duration, before the transmit carrier is
inhibited the demodulator must be unlocked continuously for the selected time
period (1, 2, 4, 7, or 10 seconds).
Enabling RTI does not affect the Internal IF Loopback feature. However, be
aware that, if an External IF Loopback is attempted (i.e., connecting an external
cable from the Tx IF output to the Rx IF input), this will not work! (The Tx
carrier cannot turn on until the demod is locked – the demod cannot lock
because the Tx output is off. The net result is that the demod will not lock and
the Tx carrier will not turn on.
Power-On Carrier-Off (POCO) – When enabled (selected as ON ), this feature overrides the Tx
setting to OFF in the event of a power-cycle of the modem. Use with caution.
SPECTRUM INVERT should normally be in the OFF position. For all FEC types
except BPSK, when Spectrum Invert is in the ON position the transmit
spectrum is inverted (which is the same as reversing the direction of phase
rotation in the modulator). In BPSK, the time-order of bits out of the FEC
encoder is reversed to make the modem compatible with certain other
manufacturer modems.