Electro-Metrics EM-2115, Инструкция по эксплуатации

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EM-2115 APPENDIX C FUNCTION AND DESCRIPTION
(EM2115C-2)
C-3.0 Circuit Description
Sections 4.0 through 12.0 briefly describe the major modular and pc board circuitry of the
EM-2115.
C-4.0 A2 RF Tuner Module
The A2 RF Tuner selects RF signals between 9 kHz and 1 GHz and converts them to one
of three IF frequencies (175 kHz, 1.6 MHz, 8.7 MHz) depending on the frequency of the input
signal.
The RF Tuner Module contains the following subassemblies:
a. 15 RF Frequency Bands (A2A1-A2A15).
b. Stator Board Assembly (A2A16A1).
c. Preamplifier/Tuning Regulator Board (A2A16A2).
d. LO Amplifier (A2A16A4).
e. IG Calibrator Assembly (A2A16A5).
f. RF Input Attenuator (A2A16A6).
g. Gear Train Assembly (A2A16A3).
C-4.1 A2A16A6 RF Input Attenuator
The signal from the RF Input Connector is applied via the 1 GHz low pass input filter to
the programmable 0-100 dB step attenuator. The output of the attenuator is applied to the IG In-
put Connector (A2A16A5J1) on the IG Calibrator Assembly.
The RF Input Attenuator is controlled by logic comands from the Microprocessor Assem-
bly (A1A3).
C-4.2 A2A16A5 IG Calibrator Assembly
(Refer to Figure H.1)
The IG Calibrator produces a series of narrow pulses, repetition rate approximately 80
Hz, for use as the calibration transfer standard for the receiver.
The IG Output (A2A16A5J2) is switchable between the output of the impulse generator
circuit (IG activated) and the RF signal input from the RF Input Attenuator (IG de-activated).