FSK/MSK/GMSK/GFSK modulator COM-1128 -> FSK demodulator COM-1127 -> BER measurement COM-1005.  

Test configuration example in 1128_1127_1005.stn settings file: 
- 16 Mbit/s, 2-FSK, no gaussian filtering, no frequency error, noiseless. 

Back to back digital modem operations can be verified at baseband. 
The FSK modulator is configured in signal generator test mode whereby a periodic 
2047-bit sequence is being transmitted. The end to end BER is measured using the 
COM-1005 module. 

Proper operation can be verified as follows:

(a) using an oscilloscope probe:

COM-1005 TP1 is high, indicating synchronization with the 2047-bit periodic test pattern 

COM-1005 TP3 is low, showing no bit error pulse 

COM-1005 TP4 shows regular periodic start of frame pulses every 2047 bits = 127.9us.

(b) from the ComBlock control center check the BER (COM-1005 status).
It will show no bit errors (REG 1 through 4) and the synchronization bit (REG5 bit0) is high.

(c) from the ComBlock control center check the demodulator lock status (COM-1127 status,
Register REG16 = 3, indicating both signal power detection and AFC lock.
Register REG12/13/14 should show a frequency error centered around zero with small variations
(typically between 0xFF0000 and 0x00FFFF)