Cobra 19 Plus - OPERATING THEORY OF PLL FREQUENCY SYNTHESIZER; Fundamental PLL Circuitry Theory

OPERATING THEORY OF PLL FREQUENCY SYNTHESIZER
FOR MODEL 19 PLUS
1. Fundamental Theory Of PLL Circuitry
The purpose of PLL (Phase Locked Loop) circuit is to generate
multiple number programable frequencies from a signal reference
frequency with quartz erystal accuracy.
A basie PLL circuit consists of reference oscillator, VCO, phase
comparator and DC filter (Iow pass filter).
With the above circuit the VCO (Voltage Controlled Oscillator)
frequency is effectively locked to the reference oscillator, and
its accuracy is as good as the reference oscillator.
Since the CB radio's adjacent channel spacing is 10 kHz (or
multiple of 5 kHz), our purpose should be to produce multiples
of programable frequencies that are spaced apart by 10 kHz.
Therefore the basie PLL circuitry is expanded as follow:
19 PLUS -1-