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Superregenerative receivers for VHF and UHF

Superregenerative (or 'superregen') receivers have been used since the early days of radio as a simple and cheap way of receiving VHF and UHF signals. Unlike regenerative sets (which are common homebrew projects for medium and high frequencies), superregens have very broad selectivity. They can normally only be used for receiving AM and wide band FM signals. Consequently they can pick up FM broadcast band signals. They are somewhat contankerous and hissy. Nevertheless for the small number of parts involved they work well and sensitivity is such that an antenna is hardly required.

The secret behind the incredible gain achieveable from a single transistor is the oscillating detector. This oscillating is a radiated signal that can be picked up on other nearby receivers. This is why though superregens will tune the VHF aircraft band it's unwise to use them there because of interference risks. I've had success with FETs such as the MPF102 in simple superregens. Keep wires short for best results. Once you have oscillation and can tune stations in try experimenting with changed component values. There may be a little distortion on received transmissions due to the 'slope detection' superregen receivers employ. That is you tune off to one side of a signal for best recovered audio. If you find you don't get oscillation or reception across the whole FM broadcast band vary component values as an experiment. Even moving parts slightly closer or away from each other can help.

The superregen experience is available to you even if you'd rather buy than build. UHF superregen receiver modules are available cheaply and make a good basis for various radio experiments.

Demonstrations of superregen receivers

Superregen receivers are also used for short range remote control and data transmission applications. Frequencies most commonly used are just above 300 MHz and around 434 MHz. Demonstrations of these are below:



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