Crystals for crystal-set receivers

 The containers that housed crystals were usually very colourful. I can't really see why there was such a large market for these unless the performance between the different types varied? Inside each box there was usually a crystal of some silvery mineral, a new catswhisker and a pair of simple tweezers.

I suppose people were always on the lookout for something better.

Such was the interest in improving one's output from a crystal set that various methods of circuit variation were tried, including the use of a battery and a potentiometer to improve sensitivity. I believe that during these experiments there must have been at least one that resulted in the first transistor. It is now impossible to judge whether this is so, but I read an article in an early magazine that came extremely close to making a point contact transistor. I also read an article concerning oscillations taking place in a crystal circuit. Impossible? No, this is certainly a fact as a tunnel diode suitably biased will impart a negative impedance to a circuit. This was formally discovered, in 1958, to produce oscillations up to several GHz, given an appropriate inductance and capacitance. The Gunn diode, another two-terminal device which can generate oscillations, can produce power up to 100GHz.









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