Technical description
HF SSB Transceiver 9323/9360/9390/9780 Technical Service Manual 4-39
When the power is switched on, a 13.6 V regulated supply IC2 on the Power
Amplifier [1 04-01817 (HF 4000 series)] is connected via the interconnecting
cable to P2/1 and 2 on the PA/Exciter Interface PCB. From here it is fed through
L4, F1, L1 and P1/5, 6, 7 and 8 to the Microprocessor and Audio PCB. At the
same time it provides 13.6 V to IC2 and switching transistor V1 on the PA/Exciter
PCB. V1 provides the supply to power the transmit amplifier during transmit only.
At the moment of switch off the POWER ON line P1/3 goes high (12 V
approximately) and forward biases transistor V8. This energises the OFF coil of
the latching relay K1, causing contacts K1/C and D to open and remove the
ground on the POWER ON line to the Power Amplifier type 4404 (P2/6). This de-
energises relays K8 and 9, switching off the 24 V and 13.6 V regulated to the
transceiver.
Transmit Amplifier
The RF input to the PA/Exciter Interface PCB is applied to J2. From here it is fed
via a common mode transformer T2 through R17/C15 and R18 to a common base
amplifier V3. R19 preset provides a range of approximately 8 dB of gain control.
The signal at the collector of V3 is passed to an emitter follower V4, the output of
which drives V5.
In combination with T3, V5 forms a fixed gain feedback amplifier. The secondary
of T3 is adjusted for 2.0 V PP output by R19. This occurs when the exciter is
modulated with a single tone into compression while connected to the 4404 PA
assembly.
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The output of T3 must be terminated into 50 Ω if it is not connected to the Power
Amplifier type 4404 when adjusting R19.
Receiver Path
The received signal from the PA assembly is applied via the connecting cable to
Rx I/P between P2/10 and 9 (AC ground). It is fed via C14, input protection
diodes D1 to D4 and common mode transformer T1 to J1. From here it is coupled
by a coaxial cable to the receiver input on the Rx/Exciter PCB [1 04-02972 and
04-03135].
Antenna Control
The Antenna control cable connected between P202 on the Microprocessor and
Audio PCB [1 04-02976] and J201 mounted on the rear panel is also connected
via P3/6, 7 and 9 to the PA/Exciter Interface PCB [1 04-03092]. This enables
the SCAN, TUNE and TUNED IN control lines to be connected to the PA
assembly 4404 via the connecting cable between the two units.
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