It is amplified by the transistor amplifier. The gain of it was 26dB. Please use the transistor having ft about 1GHz. Double gate FET converts the signal to 390kHz signal. This circuit is modern type of 6BE6 self oscillating convertor. Second gate is oscillator.
First gate is signal input.
This receiver has no IF amplifier. This detector has high impedance output. The audio amplifier has 11dB gain. The capacitor of the gate is used not to make self oscillation. I will explain about transmitting time.