Battery Powered Tube Regenerative Receiver

Basic Regen design is pretty common, so BEFORE the schematic comes the `concept stage`, the `what`s available in the junkbox stage`, back to the `concept stage`, followed by the `mechanical/electrical layout stage`, then sketch a rough schematic. and do it all over again. The BC-221 has always impressed me as having about the simplest, smoothest,
Battery Powered Tube Regenerative Receiver - schematic

no backlash, tuning mechanism which is readily available to us. In fact, I picked up another two beat up BC-221 derivatives (forgot the numbers) at the last swapfest, one for $5 and one for $7. can`t beat that for really good parts including the covers. This is a Regen and all Regens should be breadboarded on a piece of plywood (personal opinion based on my first experience). An 8" x 9" breadboard looks about right and will fit inside the diagonally cut covers of and old BC-221 derivative (see the picture). The tuning mechanism and variable were mounted on the "front" panel and the panel was reinforced with extra ribs to reduce flexing. Having both the tuner mechanism and the variable capacitor on the same panel prevents additional movement. Selection of a good "solid" coupler and alignment of the 2 shafts is important. If you use shims, you still need solid mechanical mounting and aluminum is easy to work. After measuring the coil with my invaluable AADE L/C Meter and doing a little figuring, the coil I had picked out should cover the desired frequency range with 4 taps and a smaller value tuning capacitor for the higher frequencies. Molex connectors were chosen for the taps because they are a good connection (better than a clip), cheap, and provide the shortest lead length. The coil was located to give the tuning capacitor plenty of room and to allow for installing a shield if necessary. The antenna and ground connections...

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