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CDM-600 Satellite Modem Revision 7
Front Panel Operation MN/CDM600.IOM
6–14
6.3.1.4 CONFIG: RX
The sub-branches available are:
CONFIG: RX: RX-IF
Edit the Acquisition Sweep Range of the demodulator. The value of the digit is changed
using the [↑] [↓] arrow keys. Press ENTER.
The value entered determines the amount of frequency uncertainty the demodulator will
sweep over in order to find and lock to an incoming carrier. When operating at low bit
rates, large values of sweep range (compared to the data rate) will cause excessively long
acquisition times. For example: selecting ± 32 kHz with a data rate of 2.4 kbps, BPSK,
will result in an average acquisition time of around 3 minutes.
Edit the Receive Frequency (RX FREQ) of the demodulator. Select the digit to be edited
using the [←] [→] arrow keys. The value of the digit is changed using the [↑] [↓] arrow
keys. Press ENTER. Note that the range is from 52 to 88 MHz, and 104 to 176 MHz. The
resolution is 100Hz.
For units manufacured after February 2005, and which display CDM-600(E)on the
opening menu, the range of IF frequencies has been extended to 50 - 90 MHz, and 100 -
180 MHz.
IMPORTANT
SPECTRUM INVERT should normally be in the OFF position. When in
the ON position, the receive spectrum is inverted (which is the same as
reversing the direction of phase rotation in the demodulator). Note that in
BPSK mode, the demodulator will automatically synchronize to either the
normal time-ordering of bits FEC codeword pairs, or the inverted ordering
used by certain other manufacturers.
RX-IF DECODER DEMOD DATA DESCRAM EbNo
DATA=00064.000kbps SYMBOL=00037.333ksym
ACQUISITION SWEEP RANGE = +/- 32 kHz
RX FREQ=070.0000 MHz SPECTRUM INVERT=OFF