BENDIXKing KY 96A, Maintenance Manual

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B
KY 96A, KY 97A
Rev 5, Apr 2003 MM 006-05674-0005.dwd Page 4-1
SECTION IV
THEORY OF OPERATION
4.1 GENERAL
The KY 96A, KY 97A Comm Transceiver is comprised of:
A. A single conversion VHF receiver utilizing a four pole varactor tuned prese-
lector, field effect transistors for the RF amplifier and mixer, an 8 pole mono-
lithic crystal IF filter and integrated circuit IF amplifier.
B. A broadband transmitter with power transistors mounted on a die-cast alu-
minum heat sink followed by a three section elliptic function low pass filter.
C. A control section utilizing a microprocessor to:
1. Increment or decrement the selected frequency.
2. Store the “USE,” “STBY,” and 9 user programmable channels in non-vola-
tile memory.
3. Remote transfer the “USE” and “STBY” frequencies and remote increment
the stored channels.
4. Light the display with a digital liquid crystal readout and control dimming of
the display.
5. Generate frequency code for the synthesizer.
D. A power supply made up of a discrete 9 volt regulator, 3 terminal 5 volt reg-
ulator.
E. A liquid crystal frequency display with variable backlighting and viewing an-
gle.
4.2 GENERAL CIRCUIT THEORY
4.2.1 Receiver
A receiver block diagram is shown in Figure 4-1 . The received signal passes through
the low pass filter on the transmitter PC board and the T/R diode to the dual gate field
effect transistor RF amplifier. The desired signal proceeds to the dual gate FET mixer
Q103 where it is converted to 11.4 MHz, and fed through the monolithic crystal filter to
the integrated circuit IF amplifiers followed by the detector. Automatic gain control
voltage is fed back to the first and second IF amplifiers and the RF amplifier to achieve
more than 120 dB of dynamic range. The detected signal is not allowed to pass
through the squelch gate until the input signal has:
A. Exceeded the noise squelch setting or,
B. Exceeded the carrier level setting.