Radio circuits built


Posted on Feb 6, 2014

This receiver is a modification of Charles Wenzel`s Two Transistor Reflex Radio. Instead of a ferrite AM loopstick antenna, I use a magnetic loop antenna, and I added an LM386 amplifier stage to drive an 8-ohm speaker. There is a switch to select whether this amplifier should be used to power the speaker or whether crystal earphone listening is d


Radio circuits built
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esired. I use six AA rechargeable NiMH batteries to provide the 8V power supply, but a 9V alkaline battery or a 6V lantern battery work just fine. I think even a small solar cell array would suffice to power this thing if you were camping on a sunny enough day! Prototype receiver on breadboard. I will soon move all parts currently mounted on the breadboard to a soldered circuit board. I will also add interface connections with screws on the wood base, so that I can swap out other receiver modules to the same wooden box. Update 25 August 2009. The finished AM receiver. The detector and audio amplifier circuitry is now soldered to a permanent circuit board. I added a handle to make it easy to carry the radio around. Close up view of the inside of the finished receiver. I have the schematics folded up inside a small zipper-style plastic bag, attached to the inside of the wood frame using Velcro. The screw connections facilitate removing the circuit board and replacing it with other experimental designs. The magnetic loop antenna is depicted as a transformer. It is actually a pair of hand-wound rectangular loops of enameled magnet wire, about 5. 5 inches by 4. 5 inches. If I build another one of these receivers, I will wrap maybe 16 or 18 turns instead of 20 on the tuner side to bring down the inductance so that I can tune higher on the AM band. The antenna is highly directional. You have to rotate the radio to aim it at the...




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