Technical description
4-24 HF SSB Transceiver 9323/9360/9390/9780 Technical Service Manual
A/D inputs
The microprocessor IC101 [1 04-02976 Sheet 1] monitors the supply voltage
and VSWR signals applied to the A/D input:
• The supply voltage ("A" rail) is applied via resistor divider R107 and R111 to
IC101 pin 1. The microprocessor provides a low alarm tone when the supply
drops below 10 V.
• The transmit forward power detector output from D1 (FWD–PWR line) on the
PA assembly [1 04-02973 and 04-03096] is applied via a coupling cable to
resistor divider R108 and R112. It is then applied to IC101 pin 68.
The transmit reflected power detector output from D2 (REFL–PWR line) on
the PA assembly is applied via a coupling cable to resistor divider R109 and
R113. It is then applied to IC101 pin 67.
The microprocessor IC101 compares the forward and reflected power when in
the Tune mode. It also provides a visual indication on the LCD of the measured
VSWR when the special Test mode is enabled.
Applications that will be available in the future are:
• AGC voltage derived from the Rx/Exciter PCB will be connected via a
coupling cable to a resistor divider R110 and R114, then to IC101 pin 66
• temperature measuring circuit R72, R73 and R74, shown on the Rx/Exciter
circuit [1 04-02972 Sheet 1], is to be fitted on the PCB
Antenna control
The connector J202 [1 04-02976 Sheet 2] provides an interface to automatic
antenna tuning systems, antenna selectors or band select for external power
amplifiers.
The antenna control has a 4–bit binary output (pins 1, 2, 9 and 10). Three of these
bits (pins 1, 9 and 10) can be programmed to provide information on the selected
channels or bands. Pin 2 is used for special functions, e.g. detection of an external
LPF.
The channel number is obtained by decoding the binary code. When the binary
code is decoded, binary one is channel 1 then it follows the channel numbers up to
channel 8. It then starts a zero for channel 9, a one for channel 10 and so on.
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