Simple Two-Transistor Radio

Published:2012/10/22 22:07:00 Author:muriel | Keyword: Simple, Two-Transistor, Radio | From:SeekIC

Here is a simple radio that was designed to minimize unusual parts; there isn't even a detector diode! The sensitivity isn't as high as the one-transistor reflex but the simplicity is attractive. Strong stations will provide plenty of volume into a crystal earphone or an external amplifier. The AM Loopstick was purchased on eBay but the enterprising experimenter can swipe one from the interior of a cheap radio. If the loopstick has more than one winding, use the one with the most turns. Wind 3 or 4 turns near one end of the winding as seen in the photo. The tuning capacitor in the prototype is from an old radio and the little plastic dial was cut down such that it just fit into the back of a black pointer knob. The fit was tight so no glue was needed. All of the sections of the capacitor were connected in parallel to get the most capacitance for this loopstick. All the other parts are common. The transistors can be just about any small-signal type. The prototype uses the metal can 2N2222, primarily for looks. Some transistors may have too much high frequency gain; if the circuit squeals, try adding a small resistor in the emitter of the first transistor, maybe 47 ohms, the smaller the better as long as the circuit is stable. The large 47 uF could be smaller in most cases but the circuit can pick up hum if the wires are too long. Don't leave out the large capacitor across the battery, it provides needed low power supply impedance.



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