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CDM-Qx Satellite Modem Revision 5
Front Panel Operation MN/CDMQx.IOM
5–24
(ConfigTxTxα) – TX Roll-Off (α) factor
Select 20% or 35%, using the ◄ ► arrow keys, then press ENT. The default is 35%.
5.6.1.3 (ConfigRx) - RECEIVE
The sub-branches available are:
Select FEC, Dem, Code, Data, Frq, Acq, Descram, Buf, Inv, Misc, or CnC® using
the WXarrow keys, then press ENT. The user will then be taken to a further sub-menu.
Each of these choices is described briefly in the table below:
FEC
(Forward Error Correction) This sub-menu permits the user to select the method of
FEC used for reception (Viterbi, TPC, etc.). FEC type takes the highest configuration
priority.
Demod
(Demodulation) This sub-menu permits the user to select the modulation type used for
reception (BPSK, QPSK, 8-PSK, etc.). The available choice of demodulation will
depend on the FEC type chosen.
Code
(FEC Code Rate) This sub-menu permits the user to select the FEC Code Rate used
for reception (Rate 1/2, Rate 3/4, etc.). The available choice of Code Rate will depend
on both the FEC type and Demodulation selected.
Data
(Data Rate) This sub-menu permits the user to select the receive data rate, in steps of
1 bps. The choice of data rate will depend on the FEC type, Demodulation, and Code
Rate selected.
Acq
(Acquisition) This sub-menu permits the user to determine the amount of frequency
uncertainty the demodulator will search over in order to find and lock to an incoming
carrier.
On/Off
This sub-menu permits the user to control the output state of the transmit carrier.
Descram
(Descrambler) This sub-menu permits the user to select whether or not data
descrambling is used.
Buf
(Buffer) This sub-menu permits the user to select whether or not the
Plesiochronous/Doppler buffer is used, and if so, the size of that buffer.
Inv
(Inversion) This sub-menu permits the user to invert the sense of the received
spectrum, or to invert the sense of the received baseband data.
Misc
(Miscellaneous) This sub-menu will allow the user to select Eb/No Alarm Threshold
(EbNo) and Rx roll-off (alpha) factor Rxα.
C-in-C
(Carrier-in-Carrier®) This sub-menu allows the user to set-up the carrier-in-carrier
parameters.
Rx:FEC Demod Code Data Freq
Acq Descram Buf Inv Misc CnC
Tx Roll-off: 20% 35%
(◄ ►, ENT)