Watkins-Johnson Company WJ-8718-19/FE Instruction Manual page 88

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WJ-871«-19/Mi Hi- KtUtlVLK CIRCUIT DESCRIPTION
d. 2nd IF Output - The 10.7 MHz 2nd IF output is provided as an
input to the IF/Demodulator Section. This output is 50 ohms
at 50 kHz bandwidth and is nominally 15 dB above the RF
input level.
3.2.4 IF/ DEMODULATOR SECTION
A general discussion of the IF/Demodulator Section functions and signal
interfaces is provided in the following paragraphs.
3.2.4.1 IF/Demodulator Section Functions
The IF/Demodulator Section performs the following functions:
a. Frequency Translation - The 10.7 MHz 2nd IF is converted to
455 kHz (3rd IF) by a single conversion process.
b. Bandlimiting - The 3rd IF signal is routed through one of five
selectable IF bandpass filters. Filter bandwidths are 0.3 kHz,
1.0 kHz, 3.2 kHz, 6.0 kHz, 50 kHz and 2.2 kHz USB/LSB.
c. IF Amplification - A two-stage, high gain, 3rd IF amplifier
provides the major portion of overall receiver gain.
d. Gain Control - An AGC detector provides primary gain control
to the 3rd amplifier under normal signal conditions, and
secondary gain control to the RF/IF Conversion under high
input signal conditions.
e. Signal Demodulation - Three signal demodulators provide
demodulated AM, FM and CW/SSB audio outputs.
3.2.4.2 Input/Output Signal Interfaces
The following input/output signals interface with the IF/Demodulator
Section:
a. 2nd IF Input - The RF/IF Conversion Section sends the 10.7
MHz 2nd IF input signal. Signal bandwidth is 100 kHz and
input impedance is 50 ohms.
b. 3rd LO - The Synthesizer Section sends the 3rd LO signal,
11.155 MHz, to operate the 3rd Mixer.
c. BFO - The Synthesizer sends the BFO signal, 447.1-463.9 kHz,
to operate the CW/SSB detector.
d. BW Select - The Digital Control Section sends a 5-bit data
word to select each of the five 3rd IF filters.
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