Comtech EF Data C5 - Manual (Page 230)

System Checkout C5/K1/K3 Integrated Satellite Terminal System
Rev. 0 6-6
6.2.2 Demodulator Checkout
Use the following procedure to test the demodulator.
1. Set up the equipment as shown in Figure 6-1. Refer to Chapter 2 for the
demodulator specifications.
2. Set up the IDU with an external IF loop and level. Use a properly operating
modulator, and ensure that power levels, data rates, code rates, etc., are
compatible.
3. Allow the IDU to lock up. Depending on the up and down conversion of high or
low mix. (See Figure 6-4.) When the green carrier-detect LED is on and the
demultiplexer lock fault has been cleared (where applicable), the IDU will run at
the specified error rate. Run the transmit power level (input amplitude) over the
full range, and offset the transmit frequency from the receive frequency by
35 kHz. Ensure the IDU still runs within the specified error rate.
4. Set up the IDU to check the constellation patterns with an oscilloscope that is set
in the X-Y mode. Typical constellation patterns with noise and without noise are
shown in Figure 6-5. These test points are available on the auxiliary connector
(J9, pins 6 and 8). It is not necessary to open the modem to look at these test
points.
6.2.3 ODU Checkout
1. Connect the cable between the IDU TX output and ODU.
2. Enable the ODU (Utility Modulator Fault).
3. Verify no ODU faults are reported at the IDU.