User Manual

STTRS DOCUMENTATION
Document Number 80-330501HBKM – Issue A - Draft Page 329 of 500
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.
The detector comprises of a 50Ω transmission line with a resistive tap which samples a small portion
of the mainline power. The sampled signal is amplified and fed to a conventional half wave diode
rectifier, the output of which is a DC voltage proportional to the RF input signal.
This DC voltage is passed via an inverting DC amplifier with integrating characteristics, to the output,
which drives the attenuation control line of the corresponding AGC attenuator. This unit is fitted at
some earlier point in the RF circuit.
For small signals, below AGC onset, the output control line will be close to 12V and the AGC
attenuator will have minimum attenuation. As the signal level increases the control line voltage will
fall, increasing the attenuator value and keeping the system output level at a constant value.
AGC Specification (both types)
PARAMETER SPECIFICATION
Frequency range up to 1000MHz
Attenuation range 3 to 30dB
Attenuation steps continuously variable
VSWR better than 1.2:1
RF Connectors SMA female
attenuator 1W Power
handling
detector/amp >30W (or as required)
operation -10°C to +60°C Temperature
range
storage -20°C to +70°C
attenuator pcb 50 x 42 x 21mm
Size
detector/amp pcb 54 x 42 x 21mm
attenuator 90grams
Weight
detector/amp 100grams
18.3.3.9. 12V (Single) Relay Board (80-008901)
The General Purpose Relay Board allows the inversion of signals and the isolation of circuits. It is
equipped with a single dual pole change-over relay RL1, with completely isolated wiring, accessed
via a 15 way in-line connector.
The relay is provided with polarity protection diodes and diodes for suppressing the transients caused
by "flywheel effect" which can destroy switching transistors or induce spikes on neighbouring circuits.
It’s common use is to amalgamate all the alarm signals into one, volts-free relay contact pair for the
main alarm system.