Technical description
HF SSB Transceiver 9323/9360/9390/9780 Technical Service Manual 4-17
The 7304 kHz oscillator (part of IC9) is divided down to a 2 kHz reference
frequency. The VCO signal applied to IC9 pin 4 is also divided to produce 2 kHz
when at the nominated frequency. Both of these signals are applied to the
phase/frequency detector in IC9.
The phase/frequency detector provides two outputs. Pin 15 provides a "go down"
pulse. Pin 14 provides a "go up" pulse. When locked, these outputs are high
(+5 V) except for a very narrow low pulse that occurs simultaneously on both
outputs.
V13 and V16 provide a 3 mA discharging current pulse whilst IC9 pin 15 is low.
V12, V18, and V17 provide a 3 mA charging current pulse whilst pin 14 is low.
These current pulses accumulate in the loop filter (C106, C107, C151 and R70).
The resulting voltage is applied to the varicaps (D20 - D23) via a filter (R51 and
C96). This filter removes any reference signals from the control voltage.
VCO2 and phase lock loop (04-02972)
1 04-02972 Sheet 1
The tuned circuit L40, C130/131, C132 and C133 sets the appropriate frequency
of operation. The network (consisting of C128, Z4, D31 and L39) is equivalent to
a voltage controlled, very high Q series tuned circuit. This network effectively
grounds the gate of V14 at the series resonant frequency. This determines the final
frequency of oscillation.
The oscillator drive output from capacitor divider C132 and C133 is applied to
mixers IC7 and IC8 and the prescaler IC12 (all pin 5).
The phase locked loop (PLL) incorporates VCO2. It works in a similar manner to
the phase locked loop that incorporates VCO1. The only exceptions are that the
phase detector output (IC13 pin 17) is required to drive the loop amplifier IC14/A
and that the phase comparator varies from 1.1 kHz to 2 kHz. This allows the phase
comparator frequency to vary, enabling the loop to move in 10 Hz steps while still
having a relatively high phase comparator frequency.
The 7304 kHz reference oscillator output from IC10 pin 8 is applied to the PLL
IC13 pin 2.
The DC output of the loop filter IC14/A pin 1 is applied via L36 to the varicap
D31. It controls the frequency of the VCO. Components L36, R80 and C127, form
an LPF to control the DC, while presenting a high impedance to the oscillator
circuit. Component IC14 is powered from the 18 V output of the charge pump
power supply IC11 and associated components.
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