Super Star SS-158EDX, Руководство по обслуживанию, Страница: 13 / 48

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CHAPTER 3
CIRCUIT DESCRIPTION
3.0 INTRODUCTION
This section explains the technical theory of operation for the SS
－
158 EDX mobile
AMATEUR radio.
3.1 PLL CIRCUIT
The Phase Lock Loop (PLL) circuit is responsible for developing the receiver’s first
local oscillator signal and the transmitter’s exciter signal. The PLL circuit consists
primarily of IC2, IC3, IC4, IC5, Q25, Q27, Q28 and Q29. The PLL circuit is
programmed by the rotary channel switch GPS-501. The GPS-501 & Band switch
communicates the correct binary data information to the into IC4&IC5. Sum binary
code inside IC3 then controls the VCO (Voltage Controlled Oscillator) to oscillate on
the correct frequency. This signal is fed either into the receiver’s first mixer (for
receive operation) or the transmitter’s mixer (for transmit operation).
3.2 RECEIVER CIRCUIT
The incoming RF signal comes into the radio via the antenna and into the front-end
pre-amp, Q17. The RF signal is fed into the mixer circuit of Q18/Q19 and then into
the AM/FM/SSB IF section of the receiver. AM/FM IF signal is into FL2 by
Q10,Q11,Q12 AMP,AM signal then detected by the AM detector(D30,D31) and then
fed to the audio amplifier(IC8) section of the receiver and finally out to the
speaker.FM signal then detected by the FM detector(Q12,L4) fed to the audio
amplifier(IC8) section of the receiver and finally out to the speaker.SSB IF signal is
into FL3 by Q20, Q21, Q22, Q23 AMP,SSB signal then mix with be from X4’
frequency and then fed to the audio amplifier(IC8) section of the receiver and finally
out to the speaker.
3.3 TRANSMITTER MODULATION CIRCUIT
(1)
The transmitter modulation circuit modulates the low-level RF signal from the
PLL exciter circuit with the user’s audio voice signal from the microphone. The
audio from the microphone is then amplified and fed into the transmit amplifier
circuit.
(2)
If the transceiver is in the AM mode, the AF power amplifier modulates the last
RF amplifier, which produces a true amplitude modulated RF signal.
(3)
If the transceiver is in the SSB mode, the audio signal is mixed with the
10.6975MHz oscillator in IC6.
(4)
If the transceiver is in the FM mode, the audio signal is mixed with the
oscillator in IC2.