build one transistor fm radio


Posted on Feb 5, 2014

The simple FM radio circuit got lost during the transition from vacuum tubes to transistors. In the late 1950s and early 1960s there were several construction articles on building a simple superregenerative FM radio. After exhaustive research into the early articles and some key assistance from a moder


build one transistor fm radio
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n day guru in regenerative circuit design, I have developed this simple radio kit. It is a remarkable circuit. It is sensitive, selective, and has enough audio drive for an earphone. Read more about theory behind this radio on the low-tech FM page. Except the the circuit board and battery, all parts are from Mouser Electronics. A complete parts list with stock numbers is listed below. The circuit board is available through FAR Circuits. The variable capacitoPrinted circuit board Connect the two sections of the variable capacitor (C3) in series to linearize the tuning somewhat. That is, use the connections on either end of C3 and don`t use the middle lead. L2, the RF choke should not be near a ground. The same is true for L1. Capacitance to ground will disturb the feedback. The gain is just enough to drive an earphone. If you live too far away from radio stations, you might have trouble hearing one. There is no option here for an external antenna (that would require and extra transistor). If you want a little more audio gain, or you cannot locate a TL431CLP chip, you can use some other audio amplifier in the circuit where pins 1 and 2 of D1 normally connect. You can use an LM386 or a TDA7052 audio amplifier. Quasar DIY project kit #3027 is a complete TDA7052 audio amplifier kit and it works fine in this application. Because this is a superregenerative design, component layout can be very important. The tuning capacitor, C3,...




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