How I built a shortwave Armstrong FET regenerative receiver


Posted on Feb 7, 2014

I had never worked with ` common base` or `grounded base` designs before and you know, I still don`t understand how they can amplify. Another thing, I had never used a bipolar transistor in a regenerative stage before, but had read that the amplification factor of a bipolar transistor in a regenerative receiver is actually much higher than for a FET


How I built a shortwave Armstrong FET regenerative receiver
Click here to download the full size of the above Circuit.

(I have since learned that an element with too much amplification makes for very unstable regeneration control - like this one had). Another thing that intrigued me was Mr. Kitchen`s so-called " Floating Diode Detector. " I would have never believed that you could get away without a DC bypass of some kind, but there it was and I just had to try it. Finally, I had never seen a LM386 audio amplifier IC configured for high impedance like this and I wanted to see how well it would work. I began stuffing the circuit board with parts and soldering them in. For a coil form I used a pill bottle I got at a pharmacy. When complete, I mounted the circuit board and all the other parts very neatly in my little aluminum radio chassis and turned on the set. Well, I could hear radio signals, but the truth is, the radio sucked. I mean, it sucked really badly (sorry Mr. Kitchen), I can`t lie, it just sucked. I was hoping I could get this disaster to somehow work without such "squirrellyness" so I decided to add a RF stage to its front end. After looking over the circuit board, I figured that I could easily grind out a portion ofthe circuit board`s ground plane with a tiny diamond burr I have. That way, I could create the pads for an RF stage that I wanted. Well, I did, and it was easy to do and so I mounted a 2N2222 transistor for the RF amplifier and proceeded to put in all the parts for the other stages too. First thing I noticed was that...




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