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Author Topic: Cats Whisker and Germanium Diodes  (Read 3641 times)
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« on: November 18, 2001, 09:55:35 PM »

We all know which end of a Germanium diode is the Cathode end, but how about when we use a  Cats Whisker with a Galena Crystal? What would be the Cathode end?    Bill
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AB5XZ
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« Reply #1 on: November 18, 2001, 10:21:26 PM »

Bill,

For purposes of RF detection, it doesn't matter which end is which, but I understand your curiosity.

Look up the Crystal Set Society on the Web.  Perhaps there's some data there.  Also, WB5REX (Lance) has a lot of expertise in those kinds of point-contact diodes.

If all else fails, try measuring the forward and reverse resistance!

73TomAB5XZ
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AB5XZ
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« Reply #2 on: November 19, 2001, 03:44:07 PM »

Here's an answer from my friend Lance, WB5REX:

The catwhisker is the cathode. That is where they got the word "CAThode." It is from the "cat" part of the whisker! They figured that the CAT-ions had an affinity for the CAT-whisker. I never did figure out what kind of animal an "AN" was.

No...Not really!! Just kidding!

In actuality, I think the catwhisker is usually thought of as the cathode, but it can be either cathode, or anode, depending on whether the particular "Sweet Spot" on the galena is more "P" than "N", or vice versa. The galena has both "N" and "P" spots on its surface, depending on the distribution of impurities and the crystalline structure.
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