Diodes and RF

Jared Harvey

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Dec 24, 2012, 7:23:20 AM12/24/12

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Hello,

Seeing the article in QST about reverse power lead polarity protection, they noted that using a relay with a shunt diode can be an unexpected source of RF. The claim is that nearby RF can cause the (typically non conducting) diode to act as a mixer, which can then function as a source of RF. They suggest to fix it by adding a small cap across the diode. I would like to learn more about this tendency. Does anyone know of a good source for info on such a topic?

Best regards.

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Jared Harvey Operator KB1GTT

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Web page http://jaredharvey.com

AI2Q

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Dec 24, 2012, 11:17:26 AM12/24/12

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Hi Jared.

The use of diodes as passive mixers goes back a long way; they've been used for many years in lots of RF applications. There have also been reports of RFI and TVI from "diodes" such as rusty gutters and downpipes, corroded connections, etc. As you know, diode transfer curves are nonlinear, so they make for good harmonic generators and mixers. This is discussed in the Handbook.

A reference I think most hams should have on their shelves is "Experimental Methods in RF Design" by Wes Hayward, W7ZOI, Rick Campbell, KK7B, and Bob Larkin, W7PUA. It's available from the ARRL with ISBN 0-87259-879-9. Lots of good diode info there.

Attached is a JPEG file excerpt from Experimental Methods.

Vy 73, AI2Q, Alex

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Diode_mixer.jpg

Jared Harvey

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Apr 2, 2013, 7:59:01 PM4/2/13

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Hello AI2Q,

She note some interesting software defined radio
techniques. Also it's cool she made her own PCBs.

http://www.youtube.com/watch?v=YFVgq3ZB0Mo&feature=em-subs_digest-vrecs

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