2018-03-02 One Transistor AM Radio

FB group Building Transistor Radios

In JF1OZL’s voluminous archive I found his version of a MW receiver.  It is labeled [2] …. MW-RADIO (see link).  He used a long wire antenna, and an IF transformer with the ceramic capacitor removed for the tuning coil.  He also said to use a ferrite loopstick, which is what I and most others would use.
The 1N60 detector diode has a 100k resistor as a DC path to common ground.  Some experimenters don’t use any resistor, they depend on the diode’s leakage current for the DC path.  This is foolish because the leakage depends on temperature so the performance may vary – cold gives the least leakage.

The input impedance of the transistor is only a few thousand ohms, so it places a heavy load on the detector, and causes poor selectivity.  I would put another transistor between, using the common collector or emitter follower configuration so the input impedance would be very high.


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