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Some thoughts on UHF Crystal Radios
http://diyaudioprojects.com/Forum/viewtopic.php?f=16&t=5468
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Author:  vu2nan [ 02 Feb 2016, 05:41 ]
Post subject:  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.

Attachment:
untitled.JPG
Dipole with a single diode

Long diode leads may be used to form the stub.

Attachment:
untitled1.JPG
Dipole with coil and diode

A diode length of λ/4 gives a proper match.

Attachment:
untitled2.JPG
Folded dipole

A circular stub is best for minimum capacitance between the leads.

Attachment:
2.JPG
Dipole with a single diode / circular stub

Regards,

Nandu.
http://nandusthoughts.blogspot.in/2016/ ... adios.html

Author:  Geek [ 02 Feb 2016, 13:26 ]
Post subject:  Re: Some thoughts on UHF Crystal Radios

*bookmarks thread*

Author:  vu2nan [ 02 Feb 2016, 22:47 ]
Post subject:  Re: Some thoughts on UHF Crystal Radios

Thanks, OM Greg.

73,

Nandu.

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