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.
Dipole with a single diode
Long diode leads may be used to form the stub.
Dipole with coil and diode
A diode length of λ/4 gives a proper match.
Folded dipole
A circular stub is best for minimum capacitance between the leads.
Dipole with a single diode / circular stub
73,
Nandu.
http://nandusthoughts.blogspot.in/2016/02/some-thoughts-on-uhf-crystal-radios.html
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.
Dipole with a single diode
Long diode leads may be used to form the stub.
Dipole with coil and diode
A diode length of λ/4 gives a proper match.
Folded dipole
A circular stub is best for minimum capacitance between the leads.
Dipole with a single diode / circular stub
73,
Nandu.
http://nandusthoughts.blogspot.in/2016/02/some-thoughts-on-uhf-crystal-radios.html
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