QPSK modulator COM-1002 -> Dual D/A converter COM-2001 -> L-band modulator COM-4003C/D

This test setup demonstrate 
- the ability to switch between extreme L-band frequencies 
- the ability to change level
- the ability to switch between internal and external frequency reference
- the ability to switch between frequency steps
The COM-1002 is only used as a digital sinewave generator. 


(a) connect an external 10 MHz frequency reference to the COM-4003 EXT_CLK (J2) connector.

(b) import the 1002_2001_4003.stn settings into the assembly. 
Switch assembly power off and then on again.

(c) using an oscilloscope, probe the COM-2001 I and Q outputs. The capacitors C3 and C24
are convenient test points. The signals should be 100 KHz sinewaves, with amplitude
of 1Vpp.

(d) using a spectrum analyzer, check the COM-4003 output.
The output is an unmodulated carrier at 1.50 GHz. The level is -3 dBm (typ).
LO leakage is -26 dBc typ.
Image rejection for the entire assembly is -34 dBc typ.

(e) Using the ComBlock Control Center, change the REG6 to the following values and observe
the following spectrum outputs:
REG6 = x05 selects RF frequency 0, 100 KHz steps. Output is -3 dBm (typ) @ 1.5 GHz - 100 KHz
REG6 = x35 selects RF frequency 1, 25 KHz steps. Output is -4 dBm (typ) @ 1.740 GHz - 100 KHz
For every frequency, check that the SYNC_LOCK test point is low, indicating frequency
synthesizer lock.

(f) Transmit level:
Set REG4/5 from FF 03 (maximum gain) to 00 00 (minimum gain)
Output level should be reduced by at least 20 dB.

(g) Internal frequency reference:
Switch to internal frequency reference by setting REG6 to 04
Remove the 10 MHz external frequency reference.
You may have to switch the assembly power off and then on again.
Re-do step (e). 
For every frequency, check that the SYNC_LOCK test point is low, indicating frequency
synthesizer lock.