Evening Republican, Volume 21, Number 62, Rensselaer, Jasper County, 15 March 1917 — KNOW LITTLE OF CRYSTAL DETECTOR [ARTICLE]

KNOW LITTLE OF CRYSTAL DETECTOR

MOST AMATEUR ELECTRICIANS L ARE IGNORANT OF SENSITIVENESS Single Crystal Gives Better Results * * Than Combination. Ih spite of the fact that crystal detectors play so important a part in experimentation of electrical amateurs, their use is not understood as well as it should be. There are parlous combinations In use. It will be found, in general, that the more sensitive a crystal is, the more readily will it lose its adjustment or “knock out” from loud Sanais or static. The average amateur will get more satisfaction from using a single crystal than from a combination. For example, although a perikon has many desioble characteristics, there to apt to be trouble from particles of one of the crystal rubbing off and adhering to the surface of the other. This is constantly Occurring. Chalcopyrite and zincite, arsenic ?.nd silicon, and antimony and silicon are all used in combination, and are remarkably sensitive. An occasional w;.sh with carbon disulphide helps to remove grease and dirt from the surfaces, and oftgn restores them to sens>.. /eness. Carborundum is proof against all manner of knockouts, but is unfortunately not very sensitive. A stiff wire or needle makes the best contact with this substance, and should be pressed down into it with considerable force. A battery must be used with this detector Silicon is more sensitive than carborundum, and is correspondingly more easily knocked out by static. A light contact is required, and the efficiency is often improved by applying an exceedingly small potential. Galena is probably the most sensitive of the crystal detectors, but is harl to keep in adjustment. It is especially sensitive to static. The wire used should be as fine as possible. Certain violin and mandolin strings aie woimfi with very fine Silver wi re, this wrapping is more suitable for use with galena. A minute fraction may be cut off the end of the wire from time to time, thus always insuring a clean point. Cerunite requires about the same treatment as .galena. Iron pyrite works best with a firm contact and is almost as sensitive as silicon.—-Popu-lar Science Monthly.