AN EXPERIMENTAL RADIO-FREQUENCY CHOKE

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

AN EXPERIMENTAL RADIO-FREQUENCY CHOKE

A USEFUL UNIT TO CONSTRUCT

This is a radio-frequency choke for use in Reinartz or other circuits, and for convenience in trying out new. hook-ups every 200 turns is tapped, quick connection being made by moving a pin to the required position. If the approximate nuniber of turns required is known, and the choke is for permanent use, the tapping arrange:

mets may be left out. A simple way of constructing such a permanent choke

is to wind the groups of turns upon a f-inch test-tube. The overall height, as illustrated, is deep, 4-inch wide, and not less -than q-inch apart. If the spool ends are not used a small square of wood is inches, ‘Ihe central core of wood, the core of a wire spool or other suitable former of ? or 7-8-inch diameter. Vive slots are cnt or turned, 1-8-inch fitted at top and bottom, and down’ the front is a strip of ehonite, } to l-inch wide. Upon this strip are riveted five pieces of 28’s brass sheet, curled up to take the connecting pin (14’s wire) attached to the top terminal by a short flexible lead. The size of wire to be used is 36’s s.w.g., 200 turns in each slot, When passing from one slot to the next a loop is made in the wire, sufficiently long to clean up and soider to the corresponding rivet at the back of the chonite. The lower end of the coil connects to the lower terminal, and top of coil to top brass strip on ebonite. The circtiit leads are connected to the two terminals, and moving the pin puts in thie required number of turns. The wire is wound irregularly, crossing and recrossing, as this helps to keep down self capacity. The top terminal is supported upon a slip of ebonite, raised up by screwing down upon collars made by rolling up a strip of the 28’s brass sheet.