Comtech EF Data SDM-309B - Manual (Page 153)

Maintenance SDM-309B Satellite Modem
6-6–8 MN/U-SDM309B Rev. #
6.1.4 Test Points
The following is a list of front panel test points and a description or the signal that is to
be present under normal operation.
6.1.4.1 Modulator (Figure 6-5)
TPG1 Ground
TP2 Q EYE Pattern
Level is 2 V P-P. The DC offset is 0 V. This signal is the Q input to the QPSK
modulator. The eye pattern at this point is not equalized.
TP3 I EYE Pattern
Level is 2 V P-P. The DC offset is 0 V. This signal is the I input to the QPSK
modulator. The eye pattern at this point is not equalized.
TP4 Q - Analog Data Eye Pattern
Approximately 1.4 V P-P between eye sample points.
TPG2 Ground
TP6 I - Analog Data Eye Pattern
Approximately 1.4 V P-P between eye sample points.
TP17 I channel data
TTL level data that is output from the last register in the digital filter. The I channel
activity fault is monitoring the line.
TP18 Q channel data
TTL level data that is output from the last register in the digital filter. The Q channel
activity fault is monitoring the line.
TP19 Symbol rate clock
TTL level clock that is locked to the incoming data to the interface card. This clock is
at the symbol frequency and not at the data rate. the frequency is equal to: QPSK-
(DATA RATE/CODE RATE)/2 BPSK-(DATA RATE/CODE RATE)
TPG6 Ground
Figure 6-5