A2537-002/01 February 2020 4-18 SEMCO Proprietary Information
4.5.7 Remote GUI AGC Time Constant Selection
The AGC Time Constant pull-down menu is selected by clicking on the arrow icon to the right of the AGC
TC box (Figure 4-27).
Figure 4-27
AGC Time Constant Selection on Remote GUI
4.5.8 Remote GUI AGC Freeze
As previously addressed in paragraph 4.5.3, the AGC Freeze feature allows the operator to freeze (hold)
the gain of the selected receiver, and is used to measure receiver IF output SNR for Antenna G/T
measurements.
Using AGC Freeze for Antenna G/T measurements, the user measures the antenna gain by pointing the
antenna directly at the sun (“Hot Sky”), then away from the sun (“Cold Sky”) and then measuring the IF
signal power difference (i.e., antenna G/T).
The AGC Freeze mode should not be used for receiver mission support.
The receiver also has programmable attenuators in the RF Tuner design that ensures front-end protection
as well as provide for a linear and calibrated dynamic range. However, attenuator operation will sometimes
affect the accuracy of antenna G/T measurements at approximately -70 dBm to >-50 dBm noise floor
levels.
Accordingly, an Attenuator Disable feature precludes this possibility and ensures accurate G/T
measurements.
CAUTION:
The Attenuators must be TURNED ON (enabled) when
resuming normal receiver operations. Failure to do so will
impact overall receiver dynamic range and linearity.
Figure 4-28 depicts the AGC Freeze feature on the remote GUI. In addition, holding the cursor over AGC
Zero enables a pop-up notice with respect to the Attenuator Disable feature that, as previously described
is used for more accurate antenna G/T measurements. Right clicking on the AGC Zero button accesses
this feature as shown.
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