Shortwave Crystal Radio

It was my first attempt at building a shortwave crystal radio.

Shortwave Crystal Radio - Schematic
It's single-tuned and uses a 1N270 to drive vintage sound-powered phones.

The circuit was 'breadboarded' on an old fan regulator baseplate with the coil wound on a white plastic pill bottle.

Shortwave Crystal Radio
A 2-section variable capacitor, with slow motion drive, was used for tuning. The 2 sections were connected in series for an effective maximum capacitance of 180 pF.

Using a wire antenna (35' long) and earth resulted in 'local strong station breakthrough' and hum.

With earth disconnected, the breakthrough and hum disappeared and it was possible to tune-in to a faint shortwave broadcast. It was from AIR Chennai, on 7380 kHz, 300 km away.

Tuning further up, a weaker Oriental station was heard.

Severe fading was experienced with both the signals.

Similar results were obtained using a 1.5 m long telescopic antenna and earth.
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