The resulting arrangement works quite well. Tighten the screw just enough so it stays put as you tune the capacitor. The #4 screw is the wrong thread pitch and will jam (bind) in the threads. Twist the nylon screw into the threads of the C3 tuning handle. A knob is important to keep your hand away from the capacitor and coil when you tune in stations. Mount the ends of the wire on your circuit board keeping some clearance between the coil and the circuit board.Ĭ3 does not come with a knob and I have not found a source. Find the midpoint and solder a small wire for C2 there. Spread the windings apart from each other so the whole coil is just under an inch (2.5 cm) long. Wind 6 turns tightly, side-by-side, on the cylinder, then slip the wire off. #20 bare solid wire works the best, but any wire that holds its shape will do. I used a thick pencil from my son's grade school class, but a magic marker or large drill bit work just fine. Get any cylindrical object that is just under 1/2 inch (13 mm) in diameter. Although it has many important jobs, it is easy to construct. L1 sets the frequency of the radio, acts as the antenna, and is the primary adjustment for super-regeneration. If your hand is too close to L1 while you tune the radio, it will make tuning very difficult. Arrange L1 fairly close to C3, but keep it away from where your hand will be. Only the outer two leads are used the middle lead of C3 is not connected. The tuning capacitor, C3, has three leads. The variable capacitor is available throughīecause this is a superregenerative design, component layout can be very important. The circuit board is available throughįAR Circuits. A complete parts list with stock numbers is listed below. Read more about theory behind this radio on theĮxcept the the circuit board and battery, all parts are from It is sensitive, selective, and has enough audio drive for an earphone. After exhaustive research into the early articles and some key assistance from a modern day guru in regenerative circuit design, I have developed this simple radio kit. In the late 1950s and early 1960s there were several construction articles on building a simple superregenerative FM radio. The simple FM radio circuit got lost during the transition from vacuum tubes to transistors. Certainly, there are no simple FM radio kits. But, look around and you will find virtually no FM radio kits. The same circuit board can be modified for the improved one transistor radio.ĪM radio circuits and kits abound. Ask them for "Andy Mitz's One transistor FM radio printed circuit board". See the new improved version on Patrick's web siteĪ printed circuit board for the original circuit is available throughįAR Circuits.
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