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| Basic Shunt-fed Crystal Radio |
Related post: Crystal Radio Circuits - Alternative Concepts
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Ideal detector for a Shunt-fed Crystal Radio
A Germanium transistor may be configured as a diode, having its forward voltage as low as 0.1 V, by just interconnecting its base and emitter.
It makes for an ideal detector in a shunt-fed crystal radio.
Related post: Crystal Radio Circuits - Alternative Concepts
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Related post: Crystal Radio Circuits - Alternative Concepts
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Some thoughts on UHF Crystal Radios
Diode capacitance
Low capacitance diodes are a must for UHF crystal radios.
It follows that they are to be so wired that the capacitance between their leads is kept to a minimum.
This does not imply that the leads are to be cut to minimum length. In fact longer leads facilitate antenna-diode impedance matching.
Antenna-diode impedance matching
Stub matching is a must for maximizing the signal strength.
A diode length of λ/4 gives a proper match.
A circular stub is best for minimum capacitance between the leads.
Related post: UHF Crystal Radio
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Low capacitance diodes are a must for UHF crystal radios.
It follows that they are to be so wired that the capacitance between their leads is kept to a minimum.
This does not imply that the leads are to be cut to minimum length. In fact longer leads facilitate antenna-diode impedance matching.
Antenna-diode impedance matching
Stub matching is a must for maximizing the signal strength.
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| Dipole with a single diode |
Long diode leads may be used to form the stub.
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| Dipole with coil and diode |
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| Folded dipole |
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| Dipole with single-diode circular stub |
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