Comtech EF Data CDM-625 - Manual (Page 112)

CDM-625 Advanced Satellite Modem Revision 15
Front Panel Operation MN-CDM625
5–12
5.2.1.3 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 Tx-IF, Freq, Power, FEC, Mod, Data (Symb
when in IP-ACM mode), or Scrambler, and then press ENTER.
On the bottom line – Read-only Data/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.
5.2.1.3.1 CONFIG: Tx  Tx-IF
Tx: Carrier=On (Off,On,RTI) POCO=Off
SpectrumInvert=Off Txα=.35(.35,.25)()
Use the ◄ ►arrow keys to select Carrier, POCO (Power-On Carrier-Off), SpectrumInvert, or Txα
(for Tx Alpha Filter Rolloff Factor), and then use the ▲▼ arrow keys to edit the option setting
(the available choices may be shown in parentheses). Press ENTER when done.
• For the Carrier, use the ▲▼ arrow keys to select Off, On, RTI-01s, RTI-02s, RTI-04s, RTI-07s,
or RTI-10s, and then press ENTER when done.
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.)
• When POCO (Power-On Carrier-Off) is 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