Comtech EF Data SDM-650B - Manual (Page 154)

Maintenance SDM-650B Satellite Modem
6–10 Rev. 6
6.1.3.3 Sequential Decoder/Demod Card
Refer to Figure 6-9.
TPG1 Ground.
TP8
VCXO Control Voltage.
Sweeps from -2.5V to +2.5 VDC.
TP1 IMAG — I Channel Magnitude Bit.
Result of the soft bits from the soft decision interface. Transitions will occur in the
presence of noise in the RF signal.
TP2 QSGN — Q Channel Sign Bit.
Result of the hard bits from the soft decision interface. 50% duty cycle random data
is displayed.
TP3 ISGN — I Channel Sign Bit.
Result of the hard bits from the soft decision interface. 50% duty cycle random data
is displayed.
TP4 QMAG — Q Channel Magnitude Bit.
Result of the soft bits from the soft decision interface. Transitions will occur in the
presence of noise in the RF signal.
TP5 SYMBOL CLOCK.
Result of the data clock recovery loop in the demod processor section.
TP9 DECODER LOCK.
TTL levels. TTL high indicates a locked condition. A TTL low indicates an unlocked
condition.
TPG2 Ground.
Figure 6-9. Sequential Decoder/Demod Card Test Points