Valve Base Coils

Radio Record, Volume III, Issue 13, 11 October 1929, Page 25

Valve Base Coils

For Short Wave Work A NEAT and effective way of con» structing short-wave coils which are very convenient in use, is as follows. Take an old burnt-out valve, pre« ferably one with an "anti-capacity" base, and, by working the bulb and base about, detach the two. -. The necessary turns for the different wavelength bands are now wound on the base. For the 20-metre band (15,000 k.e.) the grid winding, whose ends are fastened to the grid and anode pins, consists of six turns: of No. 24 d.c.e, and the reaction windings, connected to the other two pins, of six ,turns of ‘No. 36. For the 80-metre band (10,000 k.e.) a fifteen-turn grid coil and a sixturn reaction coil, both of the gauge mentioned previously, will be suitable, It is not absolutely necessary to space the turns of the grid windings. In fact, if two coils are made up, one spaced and the other not, it is remarkable what little difference is found between their performances. ; The valve-holders used as coil mounts should be of the anti-capacity type, and should also be of the very best quality. Tappings for aerial connections are quite easily incorporated by twisting small loops at the required turns, and arranging these so that they are staggered. A crocodile clip attached to the grid terminal can now be connected to any one of these with the greatest of ease. A complete set of these coils to cover the different frequency bands is very easily constructed, and the greatly increased convenience obtained by their use more than compensates for the short time spent on their construction. :