Ranger SS-3900EGHP, Manual

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SS-3900EGHP CIRCUIT
DESCRIPTION
3.0 INTRODUCTION
This section explains the technical theory of operation for the SS-3900EGHP Amateur 10 meter mobile
transceiver.
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 IC5, IC10, TR24,
TR25 and TR26. The PLL circuit is programmed by the rotary channel switch GPS-0501. The GPS-
0501 communicates the correct binary data information to the programmable divider inside of IC5. IC5
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, TR17.
The RF signal is fed into the mosfet mixer circuit of TR18 and then into the AM/FM/SSB IF section of
the receiver (depending on the mode of operation). The signal is then detected by either the AM/FM
detector or product detector and then fed to the audio amplifier section of the receiver and finally out to
the speaker.
3.3 TRANSMITTER MODULATION CIRCUIT
(i) 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.
(ii) 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.
(iii) If the transceiver is in the FM mode, the audio signal is not mixed with 10.6975MHz oscillator but
instead phase modulates the basic exciter signal from the PLL circuit in the TX mixer.
(iv) If the transceiver is in the SSB mode, the audio signal is mixed with the 10.6975MHz oscillator
for LSB and 10.6925MHz for USB in IC3.
3.4 TRANSMITTER AMPLIFIER CIRCUIT
The transmitter takes the basic exciter signal from the TX mixer and amplifies it through a series of
amplifiers consisting of TR46, TR45, TR44, TR43 and TR56 where it is then sent out to the antenna
connector.