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CDM-Qx Satellite Modem Revision 5
Front Panel Operation MN/CDMQx.IOM
5–19
If (using the ODU, BUC menus) the user has selected a BUC LO frequency (other than
zero) and defined whether the mix is high side or low side, the display will be modified
as shown below, to include the calculated Transmit RF frequency of the modem/BUC
combination:
As the Tx IF frequency is edited the RF frequency will automatically be updated
(ConfigTxOn/Off) – TRANSMIT ON/OFF CONTROL
Select either On, Off, RxTxInhibit, or Common using the WXarrow keys, then press
ENTER.
When Rx-Tx Inhibit (RTI) is selected, it will prevent the TX carrier from being
transmitted, until the demodulator is locked.
To avoid the Tx Carrier from being turned off when the demodulator loses lock for a very
short period of time, the demodulator must be unlocked continuously for a period of 10
seconds before the transmit carrier is inhibited. This time interval is fixed and the user
cannot change it.
Having this feature enabled does not affect the internal IF Loopback feature.
But, please be aware that if an external IF Loopback is attempted (connecting
an external cable from the Tx IF output to the Rx IF input), then this will not
work! (The Tx carrier cannot turn on until the demod is locked, and 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. USE THE RTI FEATURE WITH
EXTREME CARE!
When Common is selected, this sub-menu will appear:
This will turn On or Off all the transmit path – master control for all modulators.
Tx Output State: On Off
RxTxInhibit Common (◄ ►, ENT)
Tx IF Freq: 1156.3456 MHz
RF=14156.3456 (◄ ►▲ ▼ ENT)
IMPORTANT
Tx Common Output St
a
te:
Off On (◄ ► ENT)