It’s a 40 meter (7 MHz) QRP or low power transceiver in which the transmitter is a simple crystal ... the single transistor — a J310 FET — between the two halves of the circuit.

[Qrp-Gaijin] shows how to do it with a single transistor ... He found that his original oscillator was driving an overtone crystal at its fundamental frequency. The device worked, but only ...