Winding Short-Wave Coils

Radio Record, Volume III, Issue 13, 11 October 1929, Page 29

Winding Short-Wave Coils

HE: right number of turns for a ry tuning coil to cover a particular ran, 2 ge on the short waves is not easy to determine. The turn numbers for a given diameter of former are sufficiently standardised on the broadcast band, but no two people make their short- waye coils exactly alike. To find the correct number of turns for the main tuning coil for a particular range usually entails either a good deal of "trial and error" work, or the making of a tapped coil, both processes being rather troublesome. One method of surmounting this difficulty is to procure some rubber-cover-ed flex, and with this wind on the former more turns than are likely to be necessary. Connect one end of the coil to the grid side of the tuning condenser, the other end remaining disconnected. To the filament sidé of the condenser connect a flex lead with a pin soldered on the end, This pin can be pushed \ through the rubber insulation at any ? point of the coil, and thus the correct number of turns. can be ascertained. Thé flex is now taken off, and the final coil wound on, using the number of turns required. Do not be tempted to leave the cable-wound cojl in the set aS a permanency. The odd turns at the end would produce dead-end ef‘fects, and the large amount of rubber insulation would render the coil inefficient.