This is the toroid coil variant of my
'Ferrite Loopstick Crystal Radio'.
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| Parallel-tuned Ferrite Toroid Crystal Radio |
A ferrite toroid, measuring OD 16.5mm, ID 10.5mm and H 10.5mm, is used. The coil is 25 turns of hook-up wire with a tap at 5 turns. On the primary side, a 200μH moulded inductor series-tunes the capacitive 60' long wire antenna to resonance at 612kHz (frequency of the lone 200kW local AM broadcast station). The secondary is parallel-tuned using a PVC gang condenser.
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| Parallel-tuned Ferrite Toroid Crystal Radio - Schematic |
A small plastic trinket box serves as the enclosure. A screw-type terminal strip is used to connect antenna, earth and headphones.
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| Rear of Crystal Radio with Ferrite Toroid Coil |
Reception, using sensitive balanced-armature headphones, is quite good. Headphone current, measured using a 1mA FSD 60 Ω meter, is 275 μA.
Related post: Parallel-tuned Air-core Coil Crystal Radio
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