SSB Transceiver Known as Five by Twenty

Overview

The project consists of 5 vacuum tubes without ICs or transistors for making a true SSB QRP transceiver for 20m Ham band.

Details

The device operates in true SSB by using only 5 tubes, 5W transmission, and superhet RX for driving a loudspeaker. The RX cannot be separated from TX to get the maximum possible from 5 tubes and a bunch of diodes where each tube must play a role in either mode that is similar to what is normally done with the SSB filter in all commercial SSB transceiver.

Several switches are required to reverse the signal path from antenna to audio and vice versa since each block works in both RX and TX. A total of 8 switches from 3 relay will be driven simultaneously by the PTT switch on the microphone. The main step is done by the tubes where about 140dB total gain from antenna to speaker can be obtained by just a 4-stage lineup.

Since the relays chosen are rated with 12V a voltage doubler from the 6.3VAC of the tube heaters was used. The bandpass made by inductive coupled T1 & T2 filters the antenna signal.