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Wednesday, 1 July 2015

Rejuvenating your crystals

During the 1920's, the "Daily News and Westminster Gazette" had a regular column called "Better Radio Results". I have a few cuttings of this column, and since we are all looking for better radio results I thought I might share them.

The first is for the benefit of those employing galena crystals in their crystal set, it describes a way of rejuvenating these crystals. You will be aware that many people relied on entirely passive radio receivers which employed a point-contact semiconductor diode as a.m. detector. A thin wire, known as a "Cat's whisker" was used to probe the surface of a crystal, such as galena, while listening through headphones. Natural impurities on the surface of the crystal could form a semiconductor junction to rectify, and thus demodulate the radio signals. Evidently the galena became tarnished over time and it became harder to find the "sweet spot". Here is a possible solution ...

Hopefully it will make your "cat's whisker" the "bees knees".


P.S. Unfortunately  these cuttings are undated, however this one must be after Aug 1927, because that is when the BBC Wireless Military Band was formed.

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