Electro-Metrics EM-2115, Instruction Manual

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EM-2115 APPENDIX C FUNCTION AND DESCRIPTION
(EM2115C-9)
The video signal is then weighted to obtain the time constants (charge/discharge times)
required for each detector function. Additional circuitry, for obtaining the peak level of the quasi-
peak detected signal, is located on the Audio Amplifier Board (A9).
One output of the detector circuits is applied to the front panel analog meter, while anoth-
er output is applied to the Microprocessor Board (A1A3) to be processed for use by the front
panel Digital Amplitude Display.
Logic circuitry, controlled by logic commands from the Microprocessor Board (A1A3),
activate the detection circuit required plus the correct weighting circuits.
The undetected logged video signal (AM Video) is also applied (via coaxial cable) to the
rear panel AM Video Output Connector (A13J5). In addition, a portion of the logged video signal
is applied to the Audio Amplifier Board (A9) to provide the AM audio output for the receiver.
C-9.0 A5 Discriminator Module
(Refer to Figure H.16)
The Discriminator Module produces the FM Video output for the receiver. The module
contains three separate discriminator subassemblies:
a. A5A1: 175 kHz IF
b. A5A2: 1.6 MHz IF
c. A5A3: 8.7 MHz IF.
As with the IF Amplifier Module (A3), only the discriminator circuit selected is turned
on, the remaining two discriminator circuits are turned off to prevent loading the active circuit. A
logic command from the Microprocessor Board (A1A3) activates the selected discriminator cir-
cuit by turning on the -6 VDC supply for the circuit.
The three discriminator circuits are similar in operation and general configuration.
The limited IF output from the Log Detector Module (A4) is applied to a limiter circuit to
further limit and amplify the signal before being applied to the discriminator circuit. The FM
video representation produced by the discriminator circuit is then applied through a buffer ampli-
fier to a common FM Video output connector (A5J4). A filtering network within the discrimina-
tor removes remaining IF frequency components from the FM video signal.
The FM Video signal is applied to the Audio Amplifier Board (A9) and rear panel FM
Video Output Connector (A13J6).