RELEASED: 10/2/2006
Page 42
COMMUNICATI0NS
HSD SERIES OPERATION AND MAINTENANCE
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Copyright © 2006 EMCEE Communications. All rights reserved.
This copyright notice should not be construed as evidence of publication.
The Power Combiner Module has no field serviceable parts. If a failure of the
module occurs, return the module to EMCEE for repair or replacement.
3.16 Metering Coupler:
P/N CM440159
Schematic Diagram N/A, DC2
Insertion Loss
<0.2dB
FWD Coupling
-40dB
REF Coupling
-40dB
The Metering Coupler CP1 is a four-port circuit that performs two functions. The
first function is to pass the combined visual and aural carriers (or digital carrier) with
minimal insertion loss. These carriers are then applied to the transmitter’s RF
output connector port. The second function of the coupler is to provide a sample of
the RF signals which are used by the Metering Detector. These RF signals include
a sample of the forward power from the final amplifier and reflected power returned
from the output connector.
There is no field repair for the metering coupler. In the event of a failure, return the
unit to the factory for repair or replacement.
3.17 Metering Detector:
P/N
40400053-1
Schematic Diagram 30400038, A5
The Metering Detector contains two identical circuits for monitoring forward and
reflected output power while providing dc voltages proportional to those signal
levels. A sample of the output signal from the Metering Coupler (A1CP1) is
supplied to the forward port FWD PWR Sample input (J1) of the detector. This
signal is passed through resistive attenuator R1/R2/R3 and coupling capacitor C1
to integrated circuit U1, an RMS detector. At pin 7, U1 outputs the video
component of the UHF visual carrier while C3 rolls off the aural energy contained in
the signal. The amplitude of the video is then doubled using op-amp U2 and sent
to peak detector CR1 via pins 1 and 2 of jumper JP1. (Pins 2 and 3 of JP1 are
utilized for average digital power detection only.) Capacitor C4 and resistor R7
filter the peak video component from diode CR1 and this dc voltage is sent to unity
gain buffer amplifier U2. The dc level at the output of U2 (pin 7), which is now
proportional to the peak power of the visual signal entering the Metering Detector,