SBE SB-36 OPERATION MANUAL
5.3.5.4 Side Tone Oscillator
Transistor TR-5 is a phase shift side-tone oscillator which operates
when the mode switch is in either the CW or tune position. Frequency
with phase shift oscillator is approximately 1000 kHz.
The output of TR-5 is fed to the transmitter microphone audio circuit
when the mode switch is in the TUNE position to provide a signal which
will allow tune-up of the transmitter.
In the CW mode of operation, output from the side tone oscillator is fed
to the VOX circuitry and to the receiver audio amplifier.
The signal to the VOX circuitry is used to drive the VOX amplifier
transistor, TR-13.
The side tone audio output supplied to the receiver audio amplifier is
used for operator monitoring when in CW operation.
5.3.6 Counter
The basic concept of the frequency counter circuit employed by the SB-
36 Transceiver is shown in Figure 5.3. To obtain a "RESET" and
"READ" command signal, the master clock input signal is reduced in
frequency by the clock divider chain. The “RESET" Command signal
instructs the RF counter chain when to start and when to stop
processing the RF input count-down.
The "READ" Command signal instructs the input count gate when to
pass and when not to pass the RF input to the RF counter chain.
The “READ" Command also causes the "READ" gate to turn on or off
the Nixie display tubes. The code converter circuit transposes the logic
output of the RF counter chain into driving voltages that cause the
appropriate numerals of each Nixie tube to illuminate.
The operating sequence of events for the frequency counter circuit is
as follows:
A. Momentary reset pulse clears the RF counter outputs causing the
output state to return to the starting count of zero.
B. The "READ" Command turns off the Nixie tubes for the duration of
the read-in period and also enables the input count gate to pass the
RF input to the RF counter.
C. The RF counter chain processes the RF input frequency count
NoobowSystems Lab. Tomioka, Japan 2003 http://www.noobowsystems.com/ Page 27 / 56
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