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Maintenance
The first step in turning up a carrier is to set the output frequency. This is done in the
Config menu on the front panel (refer to Chapter 4). The Config menu also allows the
operator to:
•
•
•
•
•
•
Available test modes are:
•
•
•
After the output frequency and level are set, the output is ready to be turned ON.
6.1.2 Demodulator
The demodulator supplies baseband data to the DATA I/O connector that is a result of the
QPSK modulated signal input at the IF input connector (CP2). Clock and data are
recovered, decoded, and descrambled from the input RF signal by the demodulator and
decoder cards.
The input to the demodulator card must be set within the proper frequency and power
level for the demodulator to lock to the signal. Refer to Figure 6-2 and Table 6-1 to check
for the proper E
Refer to Figure 6-2 for an example of a 1/2 rate carrier operating at an E
The (S+N)/N is measured by taking the average level of the noise and the average level
of the top of the modem spectrum, as shown. Use this measurement for the first column
of Table 6-1. Read across the page to find the S/N and E
Once the demodulator has locked to the incoming signal, the Monitor menu will display:
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•
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•
These functions are not displayed until the demodulator is locked to a carrier.
6–2
Set the output level
Turn the output ON or OFF
Set the scrambler
Differential encoder
Clock source
Gives access to the test modes for system checkout
RF loopback
Baseband loopback
CW
/N
level.
b
0
Signal level
Raw BER
Corrected BER
E
/N
b
0
SDM-650B Satellite Modem
/N
of 9.5 dB.
b
0
/N
for the specific code rate.
b
0
Rev. 6
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