User Manual

STTRS DOCUMENTATION
Document Number 80-330501HBKM – Issue A - Draft Page 117 of 500
Low Power Amplifier (12-021901) 7-Way Connector Pin-outs
Connector Pin Signal
A1 (large pin) +24V DC
A2 (large pin) GND
1 Alarm relay common
2 TTL alarm/0V good
3 Alarm relay contact (bad)
4 Alarm relay contact (good)
5 O/C good/0V bad (TTL)
8.4.3.9. Automatic Gain Control
17-001109 AGC Detector Assembly (Logarithmic)
17-001117 AGC Detector Assembly
17-001201 AGC Attenuator Assembly
The sub components 17-001109, 17-001117 & 17-001201 are parts of the Automatic Gain Control
(AGC) system used in 800MHz Line Amplifier (Ext. Amp.) (55-165401); 17-001117 and 17-001201
are paired for use in the uplink and 17-001109 and 17-001201 are paired for use in the downlink
800MHz Line Amplifier (Ext. Amp.) (55-165401) is fitted with two differing types of Automatic Gain
Control (AGC) system, one linear, and one logarithmic. The AGC with logarithmic detector (17-
001117) is fitted in the uplink path and the AGC with linear detector (17-001109) is fitted in the
downlink path
The AFL Automatic Gain Control system consists of two units, a detector/amplifier and an attenuator.
The detector/amplifier unit is inserted in the RF path on the output of the power amplifier, and the
attenuator is situated in the RF path between the 1st and 2nd stages of amplification.
17-001117 and 17-001201 are paired for use in the uplink and 17-001109 and 17-001201 are paired
for use in the downlink
The attenuator comprises a 50 P.I.N diode, voltage-variable attenuator with a range of 3 to 30dB.
The attenuation is controlled by a DC voltage which is derived from the associated detector controller
board.
Normally the attenuator is at minimum attenuation. The detector/amplifier unit monitors the RF level
being delivered by the power amplifier, and when a certain threshold is reached it begins to increase
the value of the attenuator to limit the RF output to the (factory set) threshold. Therefore overloading
of the power amplifier is avoided.
The factory set threshold is 1dB below the Enhancer 1dB compression point. Some adjustment of this
AGC threshold level is possible, a 10dB range is mostly achieved. It is not recommended under any
circumstances to adjust the AGC threshold to a level greater than the 1dB compression point as
system degradation will occur.