CDM-Qx Satellite Modem Revision 5
Front Panel Operation MN/CDMQx.IOM
5–15
5.6.1.2 (ConfigTx) - TRANSMIT
Select FEC, Mod, Code, Data, Freq, On/Off, Pwr, Scram, Clk, Inv, or Tx
α using
the ◄ ► arrow 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 transmission (Viterbi, TPC, etc). FEC type takes the highest configuration priority.
Mod
(Modulation) This sub-menu permits the user to select the modulation type used for
transmission (BPSK, QPSK, 8-PSK, etc.). The available choice of modulation 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
transmission (Rate 1/2, Rate 3/4, etc). The available choice of Code Rate will depend on both
the FEC type and Modulation type selected.
Data
(Data Rate) This sub-menu permits the user to select the transmit data rate, in steps of 1 bps.
The choice of data rate will depend on the FEC type, Modulation type, and Code Rate selected.
Freq
(Frequency) This sub-menu permits the user to select the transmit frequency, from 950 MHz to
1950 MHz, in steps of 100Hz for L-Band units, or from 50 MHz to 90 MHz and from 100 MHz to
180 MHz for 70/140MHz units.
On/Off
This sub-menu permits the user to control the output state of the transmit carrier.
Pwr
(Output Power level) This sub-menu permits the user to control the output level of transmit
carrier, either manually, or using the AUPC (Automatic Uplink Power Control) feature.
Scram
(Scrambler) This sub-menu permits the user to select whether or not data scrambling is used.
Clk
(Clock Source) This sub-menu permits the user to select the clock source for transmission. This
can be from the internal source, from an external source, or from the distant-end of the satellite
link (loop timed).
Inv
(Inversion) This sub-menu permits the user to invert the sense of the transmitted spectrum, or to
invert the sense of the transmitted baseband data or data clock
Txα
(α-Factor) This permits the user to select the modulator’s roll-off factor either 20% or 35%.
The FEC type takes the highest configuration priority, and the selection here
depends on what, if any, optional plug-in Codecs are installed. The choice of
FEC type then determines what modulation types, code rates, and data rates
are available. The order of hierarchy is therefore:
FEC type ► Modulation type ► Code Rate ► Data Rate
(Highest) (Lowest)
Tx: FEC Mod Code Data Freq
On/Off Pwr
cram Clk Inv Txα
IMPORTANT
