OCR Text |
Show Values of Grid Leak for the Best Reception The first and probably the most common use of high resistances Is to be found In detector circuits as grid leaks. In order that the vacuum tube may function at Its highest efficiency It Is necessary that the grid leak shall be of proper value, and, moreover, that it shall remain constant under all conditions both operating nnd climatic. There Is much loss of energy and considerable distortion of the reproduced repro-duced sound If the grid leak is not ot the proper value at all times. Furthermore, Fur-thermore, If the grid leak varies In resistance re-sistance value, which has heretofore been the case with the Inked paper type,. there Is danger of considerable noise In the reception. FortunatelyT when once the correct leak has been found. It niiiy be left permanently In circuit since there Is no need with present-day detector tubes of altering this value. The following table, prepared by the engineering staff of the International Resistance company, gives the correct values for metallzed registers employed em-ployed as grid leaks with the usual detector tubes: Grid Leak Vitliies Type Tubs Aver, for Weak DX Signals 200 0.5-J S-B megohms 109 I. -6 6-0 megohms WD 11 or II I. -4 4-7 meaohms 201 A 1 -5 5- megohms 200A 1. -I 1-5 megohms Since the plate voltage has somewhat some-what to do with the value of the grid leak, it goes without saying that the higher the plate voltage on the detector de-tector tube the higher the grid leak value. However, u is wen io nuv several resistors of different valuei on hand to experiment for the besl efficiency. |