Class E AM Transmitter

I’ve been dabbling in AM for a few years now so about 18 months ago I decided to build this solid state AM transmitter. Most of the stuff I use has been home-brew or vintage equipment with valves or tubes so this project was going to be an interesting alternative.

The transmitter consists of a crystal oscillator for 3615 kHz, the main AM frequency here in the UK, followed by some clever electronics which convert the sine waveform to a switching waveform which can drive FETs. The carrier generated is modulated and hey-presto we have AM.

The design was based on Steve’s W1QIX transmitter. The details of this and other Class E related info can be found on his excellent website

This is the modulator section of the transmitter:



The yellow toroids in the picture did not work very satisfactorily and had to be replaced with more low permeability cores. The modulator also contains the power supply 100v at about 10 amps or so.

Above is the RF deck with the crystal oscillator in the foreground followed by the phase splitter . The PA FETS,8 in total are mounted on the rear of the chassis.

This Class E rig works very well and with the equaliser and compressor limiter produces very nice audio.

Jet Engine Projects from Justin Woolgar