Comtech EF Data SDM-650B Specifications download pdf (Page 348)

SDM-300L3 Satellite Modem Revision 0

Specifications MN/SDM300L3.IOM

15–26

15.9.1 Receive Carrier Acquisition Range

1. The modem will automatically lock to a correctly formatted carrier, which is

within Acquisition Range

of the displayed RX frequency.

2. The operator can adjust the acquisition range from 0 to 1 MHz, in 1 Hz steps.

3. The operator can adjust the center of the acquisition range from -500 to +500 kHz,

in 1 Hz steps.

15.9.2 Receive Carrier Reacquisition

1. The modem can be programmed to delay the acquisition process upon loss of

lock. This will minimize the acquisition time for a brief loss of the carrier.

2. This delay can be programmed from 0 to 999 seconds in 1 second steps.

15.9.3 AGC Output

A programmable DC output, proportional to the receive signal level, is available at the

rear panel at 10 mA maximum, 0 to 10V. Default levels are 0V for minimum signal level

and 10V for maximum signal level. The low level (0V) can be programmed from 0 to 10V

in 0.5V increments. The high level can be programmed from 0 to 10V in 0.5V increments.

15.9.4 Doppler Tracking Performance

The modem will track the Doppler shown below with less than 0.5 dB degradation for

symbol rates ≥ 64 Ksym/s. The performance applies only to the QPSK rates 1/2, 3/4, and

7/8 with Viterbi decoding or Viterbi with Reed Solomon decoding.

• Doppler Offset

15 Hz

• Doppler Rate

20 Hz/sec

• Doppler Acceleration

35 Hz/sec

The demodulator must lock to the carrier with Doppler applied. BER is measured after

demodulator is locked to the carrier.

values in the table include the 0.5 dB added to account for degradation:

Error Criteria QPSK 1/2 QPSK 3/4 QPSK 7/8 Coding

BER ≤ 10

-6

6.5 7.7 8.8 Viterbi

4x10

Bits with no Errors 6.5 7.7 8.8 Viterbi with Reed-Solomon

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Comtech EF Data SDM-650B Specifications Page 348