THE SHORT-WAVE CONVERTER

Radio Record, Volume I, Issue 26, 13 January 1928, Page 13

THE SHORT-WAVE CONVERTER

For best results in using the shortwave converter it is necessary to provide two fixed condensers of one microfarad each, to be placed as shown in the diagram of the three-valve circuit. One is placed across the full high-ten-sion battery and the other across the high-tension output to the detector valve. There is'‘no reason against using an earth connection if it is found to give any improvement in reception. Sometimes an experimenter finds the necessity for drilling a hole in glass, but the operation appears to present many difficulties. Here is a clipping from an American paper, purporting to give away a trade secret which ‘‘makes all the difference’? in the successful drilling of glass plates. Here it is: "I have drilled as many as 100 holes per hour in opalite-so hard that an ordinary. glass cutter will not touch it. Many holes are only one-quarter of an inch from the edge of the plate, but I never cracked a glass panel while drilling. Nine-tenths of the success depends on the drill, and one-tenth on the way in which it is used. ‘The drill is n.ade by running-down the tip of a threecornered file so that the point is offcentre, and this seems to be the essence of the secret." But the matter of lubrication is just as important. ‘Turpentine is usually recommended, and it is necessary, to avoid cracking, to ensure continuous lubrication cf the fle

tip used as a drill, This is ensured by building a tiny wall of wax or putty round the position for the hole, and into this a few drops of turpentine are poured, ‘Thus the point of the tool is continuously lubricated, and the danger of an accident is practically eliminated, For a water-pipe earth connection it is a good plan to put two clamps on the pipe and solder the end of the earth wire to each. Iron pipe, although large in diameter, has a high resistance to radio-frequency currents, and causes losses, so that it is not good for the currents to traverse long lengths of piping before entering the ground, When using a buried plate of any kind, it is important that the copper wire lead should be soldered to the earthtlate, and for protection the joint may be paitited or enamelled. (End of _ Construction.)