Technical description
HF SSB Transceiver 9323/9360/9390/9780 Technical Service Manual 4-19
In LSB mode, the microprocessor IC101 latches the output of IC209 pin 9 low.
This disables the dividers IC208/A and B and enables the 1814 kHz crystal
oscillator IC206/C . The signal is then fed via the NOR gate IC206/B and the
dividers IC207/A and B (used for USB) to the modulator and demodulator. This
produces the required local oscillator frequency of 453.5 kHz.
455 kHz local oscillator for USB/LSB (04-03135)
In USB mode, the 7304 kHz reference oscillator is taken from the second
synthesiser IC10 pin 3 [1 04-03135 Sheet 1]. It is then applied via a harmonic
filter network (R268, C244, L205 and C245 [1 04-03135 Sheet 2]) to the input
of the first "divide by two" divider IC208/A pin 3. The output (pin 6) is applied to
the second "divide by two" divider IC208/B pin 11.
The enable line of dividers IC208/A and IC208/B pins 4 and 10 and the gate input
of IC206/C pin 8 are all connected to the output port of IC209 pin 9. In USB
mode, the microprocessor IC101 [1 04-02976] latches the output of IC209 pin 9
high, via the local I
2
C bus. This enables the dividers and disables the 1814 kHz
oscillator NOR gate IC206/C.
The 1826 kHz reference signal (7304 kHz divided by 4) of IC208/B pin 8 is fed
via NOR gate IC206/B to two more cascade "divide by two" dividers IC207/A and
B. This produces a balanced output signal of 456.5 kHz at pin 8.
From here it is applied via the attenuator network (R269, R270, R271 and R272)
to the balanced local oscillator inputs of modulator IC202 and demodulator IC203
pins 8 and 10.
In LSB mode, the microprocessor IC101 latches the output of IC209 pin 9 low.
This disables the dividers IC208/A and B and enables the 1814 kHz crystal
oscillator IC206/C. The signal is then fed via the NOR gate IC206/B and the
dividers IC207/A and B (used for USB) to the modulator and demodulator to
produce the required local oscillator frequency of 453.5 kHz.
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