Comtech EF Data SDM-2020 - Manual (Page 46)

SDM-2020 Satellite Demodulator Revision 4
Installation MN/SDM2020D.IOM
3–6
3.2.3 Monitor Points (J21)
The monitor points are located on a 9-pin D Sub female-connector at the rear of the unit.
The monitor functions are an aid to evaluate performance. Refer to Table 3-4 for
connector characteristics.
Table 3-4. Monitor Points (J21)
Item Characteristics
Monitor Characteristics
DC Pointing Voltage This is an aid to assist pointing an antenna. Before the demodulator is locked to the carrier the
pointing voltage is a replica of the AGC voltage (Raw). After the demodulator is locked the
pointing voltage is a measure of the eye opening. Generally,
< 2V, demodulator unlocked and
voltage proportional to AGC > 2V, demodulator is locked and the voltage is a measure of the eye
opening.
DEMOD I
DEMOD Q These are I and Q test points. They are sub-sampled so that a useful constellation diagram will
appear on the oscilloscope. Generally, an oscilloscope has limited horizontal bandwidth when it is
used in the X – Y mode. The I and Q test points are typically:
• 2.5 VDC
• 2.5V peak-to-peak VDC
M&C Monitor Factory use only.
AGC Out (Raw) This signal is proportional to the level of the incoming signal.
• 0V corresponds to maximum input power
• 10V represents minimum input power
Refer to Table 3-5 for pin assignments.
Table 3-5. Monitor Points (J21) Pin Assignments
Monitor Points
Signal Function Name Pin # Type
1 N/C
DC Pointing Voltage Point_V 2 0
DEMOD Q Q 3 0
M&C MON 4 0
Ground GND 5 GND
Not Used 6 N/U
Not Used 7 N/U
DEMOD I I 8 0
AGC OUT (RAW) AGC_OUT 9 0