CRYSTAL JOTTINGS

Radio Record, Volume I, Issue 31, 17 February 1928, Page 12

CRYSTAL JOTTINGS

The precise manner in which the rather quaint term ‘‘cat’s-whisker’’ first came to be used in order to designate the fine wire metallic cantacts which are used with many types of rectifying minerals still remains one of the insoluble mysteries of wireless science. To the average-minded wireless enthusiast who is not blessed-or cursed, as you please-with a vivid and poetical imagination, there are practically no points of resemblance to be seen between the ordinary metallic crystal tickler and the hirsute facial appendage of that noble animal, the felis domestica. EFFECT OF OXIDATION. When the volume of sonnd which is produced by the receiver diminishes, many owners of crystal sets almost invariably blame the crystal itself for the fault. But in many cases, lhowever, such diminution efficiency of the reception is often due to the cat’swhisker becoming oxidised, The remedy is to snip a small portion off the end, Cat’s-whiskers which are made of gold or platinum, of course, do not give rise to this sort of trouble, _ because they are untarnishable. How-. ever, silver takes a considerable amount of tarnish when it is exposed to some atmospheres, so that cat’swhiskers which are made from this metal are not always so free from this defect as is generally supposed.

A NOVEL CONTACT. The "brush"? contact takes the form of a uumber of fine wires bundled together, and gives very good results with a number of crystals, for when this is used a contact is always made with some part of the crystal, no matter how severe may be the vibration to which the detector is subjected. But, on the other hand, the device works badly with some varieties of crystals, for it is a fact that many radio crysals, and especially some of the patent galena ones, give by far their best results when the contact is made at a single point only. Why this should be so is by no meats clear,