Comtech EF Data SDM-650B - Manual (Page 255)

SDM-650B Satellite Modem AGC Interface
Rev. 5 E–3
E.2.2 Installation Procedure
Refer to Figure E-2 as needed. To install the AGC interface option:
1. Remove the rear panel of the modem.
2. Using the hardware provided, install the AS/0769 board to the modem
motherboard between CP1 and CP2 (IF OUT and IF IN). (Refer to Figure E-1.)
3. Attach the following wires to the motherboard:
a. E1 ⇒ GND
b. E2 ⇒ +12V
c. E3 ⇒ AGC J3, B4
d. E4 ⇒ -12V
Refer to Figure E-2.
4. Adjust R4 to achieve a reading of approximately 4.33K
Ω between U1 pin 1 and
pin 2 (refer to Figure E-3).
5. Power up the modem.
6. Adjust R5 to achieve a reading of approximately +5.75V at the right side of R2.
7. Measure the voltage at pin 1 of the 9-pin connector:
a. To achieve the minimum AGC voltage output at pin 1, set the modem input
to -55 dBm and verify the reading is 0V.
b. To achieve the maximum AGC voltage output at pin 1, set the modem input
to -30 dBm and verify the reading is 10V.
If minor adjustments are necessary, adjust the GAIN and OFFSET
potentiometers until both readings are correct.
8. Install the new back panel (refer to Figure E-1).