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| Stethoscope |
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| Piezo Transducer |
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Makeshift Piezo Earphones
A makeshift piezo earphone arrangement comprises a stethoscope and a piezo transducer.
The sound emanating from the transducer is captured by the bell of the stethoscope, held against its face.
This arrangement was recently used to figure out how to interface a piezo earpiece with a crystal radio. The transducer, a 1¾" telephone ringer, was salvaged from the junk box.
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Series-tuned Moulded Inductor Crystal Radio
'A Series-tuned Air-core Coil Crystal Radio' and 'Another Series-tuned Air-core Coil Crystal Radio' have been made simple by the use of moulded inductors instead of hand-wound coils.
This makes it possible to use a compact plastic cosmetic jar as a housing.
Related post: Another Series-tuned Air-core Coil Crystal Radio
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| Series-tuned Moulded Inductor Crystal Radio |
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| Moulded Inductor |
There is no difference between the two with respect to performance.
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| Series-tuned Moulded Inductor Crystal Radio - Schematic |
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| Another Series-tuned Moulded Inductor Crystal Radio - Schematic |
The local 612 kHz, 200 kW AM broadcast station comes in real loud with a 60' wire antenna and balanced-armature phones. Headphone current, measured using a 1mA FSD 60 Ω meter, is 625 μA.
The performance of a parallel-tuned version is also quite good with a headphone current of 300 μA.
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| Parallel-tuned Moulded Inductor Crystal Radio - Schematic |
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