Regenerative Reciever

This is the regenerative reciever that I built one night. I have been interested in vacuum tube radios, but never got off my rear and built one. Shortly after discovering the glowbugs mailing list, I broke down and built a simple 0-v-1 regenerative reciever. This reciever uses a 12SN7 dual triode, but any dual triode would work as well.

For those unfamilliar with the 0-v-1 designation, early radios had designations like this one. The "v" stood for the detector. The number preceding the "v" stood for how many stages of RF amplification there was before the detector and the number after the "v" stood for how many stages of audio amplification there was after the detector. I have only the detector stage and one stage of audio amplification. Even so, I was getting signals from Cuba and Russia with 15 feet of antenna in my apartment in Worcester MA.

Here we see a slightly better shot of the reciever. Yes, it is ugly. Yes, it is built on a piece of cardboard, and yes, it was sensitive to hand capacitance and microphonics.

The tube is a 12SN7. The transformer is a real 3:1 audio interstage transformer I got from a box at the MIT Flea. The big capacitor is the regeneration control and the little capacitor with the trimmers hanging off of it is the main tuning. I was experiementing with using trimmers to adjust the tank circut so that I would only cover a couple of hunderd KHz instead of many MHz. I was also playing with using lots of inductance to raise the Q of the tank circut. It worked but changes to the regeneration control caused pulling of the main tank. The reason for this can be cound if we draw up a regen and include the interelectrode capacitances of the tube.

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