Comtech EF Data SDM-300A - Manual (Page 388)

SDM-300A Satellite Modem Revision 6
Specifications MN/SDM300A.IOM
19–32
19.10 System Specifications
19.10.1 Loopback Modes
The operator can select one of the following interface loopback test modes.
• Baseband: Near end and far end.
• Interface: Near end and far end (Reed-Solomon or Overhead only).
19.10.2 Test Modes
Note: The TX and RX data rates must be the same for the modem to lock.
Table 19-21. Test Modes
IF Loopback: Disconnects the IF input from the RX input connector and couples it to a sample of
the TX IF output. The IF output is not affected.
RF Loopback Sets the demodulator frequency to the same value as the modulator. For the
modem to lock, an external IF loop must be provided.
BIST (Built in Self Test) The modem has the ability to generate 2 11-1 (2047) PN data and pass the data
through the Interface, Modulator and Demodulator sections of the modem. The
modem can generate noise in the IF path to simulate a satellite environment. The
true BER can then be measured by the modems built in BER monitor. This feature
can be invoked on power up or by the operator and the result checked against
specification and a fault is flagged if the unit fails. The feature can be turned off at
the front panel if so desired to minimize initialization time. The RF output is off
during this self test
2047 Pattern Generator (must
have overhead card installed
and activated)
Inserts an Industry Standard 2047 pattern in lieu of the TX data stream.
2047 Pattern Monitor (must
have overhead card installed
and activated)
Monitors the RX data for 2047 pattern. If 2047 pattern is present, this test mode
provides an indication of Bit Error Rate (BER). The RX data is not interrupted.