Transceiver Circuit with SSB 75 Meter

The circuit has been designed to produce a transceiver that switches the 4-element 1500 Ohm external BPF ends between the inputs and outputs of the two SA602s to reverse the signal flow for R/T operation.

The 2N2222 receiver RF amplifier produces 20dB of additional receiver gain since no IF amplifier is used in the design. The peak DC swing of the LM386 output produces the automatic gain control (AGC) that passed through a rectifier. This is filtered by a capacitor and fed to the gate of a BS170 enhancement mode FET which acts as a variable resistor across the LM386 input.

The chirp that occurs during the R/T transition is reduced by the diode pair in the mic circuit. The mic and audio can be muted easily by adding BS170 instead of the R/T switch directly, which can be controlled by the +R and +T voltages on their gates while their drains would be tied to the mic circuit between the two coupling capacitors and audio IN pin 1 of the LM386. By connecting the RF output collector choke of the transistor, additional power output could also be attained with a 9V.

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