LOUD-SPEAKERS ON CRYSTALS

Radio Record, Volume I, Issue 10, 23 September 1927, Page 13

LOUD-SPEAKERS ON CRYSTALS

_ Probably there are but few listeners who realise that a crystal receiver ig capable of working a small tondspeaker at sufficient strength to entertain a room full of people. ‘That this meange ‘greater enjoyment than the usual ‘take ing turns with the ’phones" goes withe out question. This applies to practically all crystal receiyers within two miles or so of the Auckland and Christchurch _ stations, and within five to ten miles of the new 2YA Wellington station. The most important part of any cry stal set is the aerial. Jt must he as long and as high as possible. Listeners should always remember that signaf strength is directly proportional to the height of their aerials. Also the heavier the wire (in gauge) the better. The Post Office makes no restrictions whatever on height or length of aerials. One hundred feet should be used at the least. ‘Two hundred feet or even more would be ideal, especially if stranded copper wire is used. oi Next in importance is the carth coffe nection. It is essential that this he the best possible. It is not snflicient to merely twist the wire a few times round the water pipe or the tap. Tf the water pipe is used, the earth wire (preferably thick insulated wire) shonté be tightly soldered to it. Care must be taken to see that the water pige actually goes iato the ground withis a short distance of where the earth wire is connected to it. Otherwise i# would be better to solder a wire io a pipe three or four feet long and them drive it into the ground just outsidé, In this case keep the ground alwayg damp by tipping water over it occasion. ally. Where possibie take your lead-in off the highest end of your acrial and ak ways have everything well insulated. Any well made home constructed se# er anv standard crystal receiver shonl@ be capable of working the loudspeaker, Of course a hig loudspeaker suitable for a multi-valve set must not be exe pected to give satisfactory results ‘a@ any distance from the broadcasting sta« tion. There are plenty of small loud speakers suitable for the purpose which can be obtained for a very slight outlay. In the writer’s opinion the ideak receiver is one which has a fixed crystab contact (commonly called a permanent detector) with a potentiometer and a small 1} volt battery to bring the cry stal up to its most sensitive condition. Carborundum for preference as this is generally recognised as one of the mos# stable detectors Known. Another point-when buying crystalg, the dealer will probably offer specimens at graded prices. Some crystals give as much volume as some valves, tie dealer hag tested them, and the pri¢é is an indication of their quality. Take | the best! However, your own crysta? set should do the work. Give it @ trial.-O.P.