Resistance checks showed that 2 windings, with a tap each, are terminated in its 6 pins. One measured 70 Ω with a 5 Ω tap and the other less than 1 Ω. A threaded core, with a movement of 5 mm is situated at the top of the unit.
The 70 Ω winding appeared to be suitable for a crystal radio. It was wired up as per the schematic shown below.
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| Chance Crystal Radio - Schematic |
(as the crow flies), comes in real loud using a 60' wire antenna and balanced-armature phones. Headphone current, measured using a 1mA FSD 60 Ω meter, is 250 μA with the core fully in and 300 μA with the core retracted.
The capacitive wire antenna series-tunes the link winding to resonance at 612 kHz, while the self-capacitance of the detector winding parallel-tunes it to resonance at the same frequency, as though the inductor/transformer has been tailor-made for this project.
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| Chance Crystal Radio |
A cosmetic plastic jar makes a good base/enclosure for this chance crystal radio.
Related post: Another Parallel-tuned Air-core Coil Crystal Radio
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