Superheterodyne Radio Uses One Tube


Posted on Feb 5, 2014

Nothing in this project is real original, but I did do a couple of modifications from the circuits I saw. The fellow that started this, as far as I can tell is Jack Bryant, KE4ID with his one tube superhet contest radio project. That was my basis for this set. I started drawing the circuit. I usually don`t release too many details early in a project but this time is different. I did


Superheterodyne Radio Uses One Tube
Click here to download the full size of the above Circuit.

get some good suggestions from my fellow radio friends, Ben Tongue and Mike Peebles. I had most of the design down but these two fine fellows gave me some extra ideas that were helpful in this design. This radio is built with the One Active Device (1AD) contest in mind. My two previous entries were done with two regenerative contest receivers. My 6SK7 and Acorn sets where the projects. They worked very well. But as time goes on, different ideas have to be tried. Jack and the others reported good results with these radios, especially when operated close to local stations. I don`t have that problem, but I just had to try it. The central part of this project is the 6BA7 vacuum tube. Using research of others, I decided that due the higher gain over other similar tubes, that this was the way to go. The other major section of this radio is the detector circuit. Looking closely, it looks like a fixed frequency crystal set. That`s what it is alright. The Bogen T725 provides a closer match between the detector diode / IF transformer and the headphones. An optional tap selector switch was added so that changing headphones would be easier. Better selectivity can be realized if you exchange the Bogen T725 for a transformer for an G berformer. The G berformer has an input impedance 5 times the Bogen and provides a much lighter load to the IF transformer secondary. The benny resistor (18k) will have to be changed to a higher value, about...




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