OUR WIRELESS CORNER.

Star (Christchurch), Volume XLIV, Issue 365, 5 March 1932, Page 18 (Supplement)

OUR WIRELESS CORNER.

FIRST THINGS SHOULD COME FIRST. By “AERIAL.” Is there a boy who prefers theory to practice—if he can get something done, without having to dig into the whys and wherefores? I doubt it. Therefore, these little talks will be “ How to Make ” ones, with just enough of the “ whys ” to enable you to understand what you are doing. I started this series at the wrong end —the cart before the horse—but that was so that you could get busy right away. Let us now go back a bit. In order to enjoy wireless several things are necessary. First of all, there must be a station operating (“ on the air,” we say) that is powerful enough and near enough for us to hear it on a Yvireless receiver. Also it must be operating (that is, working) on a waY'e-length that comes within the compass (that is, the wave-length range) of our set; e\’ery set has a limited range of wave-lengths over which it can tune, the usual broadcast band limits being from 200 to 600 metres.

The next thing necessary is an aerial system. This is sometimes called the aerial-earth or antenna-ground system. The aerial* or antenna, is a sort of wire “feeler” (antenna) that is put up into the air to enable you to catch (or collect would be better) the signals from the broadcasting station. This feeler is not' complete unless it has an “ earth ” or “ ground ” —that is, a connection (of wire, etc.) that is embedded in damp or moist soil, with, of course, the receiver in between the aerial and the ground. The next thing required is a receiver—an arrangement of coils, etc., to enable you to work on the same waY r e-length as the broadcasting station, because unless you can work on or near its waY’e-length you cannot hear its signals.

As the waves sent out by the broadcasting station move, at terrific speed, backwards and forwards (for which reason we call them “ alternating ” hence A.C. or “alternating current”) it is necessary to proY-ide something to change these alternating currents into one-way current (that is, D.C. or direct current) so that we may hear the signals in the headphones. This “ something,” it was discovered, was what we call a “ crystal,” and another inY'ention with a similar property and called in England and New Zealand a “ Y T alve,” or in America a “ tube.” I prefer the word “ valve ” instead of “ tube ” because “ valve ” exactly describes what the instrument does—it “ opens ” to let the current through one way and “shuts” to prevent the current returning back (“ oscillating.”) The “ crystal ” includes the catswhisker. Or it may be composed of two kinds of crystal (as in the “ perikon”) lightly pressing on each other or of two other kinds (as in the “carborundum”) which >are pressed very tightly together. The crystal was found to possess the \-ery curious property of allowing a “ wireless ” current (called a “ highfrequency ” current), which is A.C., to pass one way only. That is, it changed the A.C. into D.C. CORRESPONDENCE. A Wave-trap. S.J.V.R. writes:—l am writing this letter to thank you for going to the trouble of Yvriting “ ‘A Crystal Set for One Shilling,’ by J. J. S. Cornes,” partly for my benefit. I and many other boys, I feel sure, will be making this cheap set. I might haY*e had it nearly completed only I am at present constructing a,set from a plan in a book I procured from the Children’s Library, and have not much spare cash. If the above set is very successful when it is completed I will let you have the plans. By the way, would a wavetrap be very successful on a crystal set or would it cut down the strength too much? Thanking you for your help. In reply: Yes, a Yva\’e-trap would be quite a success; it would cut down the strength a little, of course, if you were using it to trap out one of the two local stations, 3YA and 3ZC, but not to any great extent. I would not advise - using a wave-trap when trying for stations outside Christchurch, as it would quite “ kill ” the faint signals. It would be better to try for distant stations at those times when the local stations are not working, when you would not need a wa\~etrap.—“ Aerial.”

CIRCLE ARTISTS, 6-3-32. Maudie Flutey, Brenetta Taylor, Daphne Dickie, Ina Hoatten, Lila Hoatten, Da\’id Guild, Beryl Scarff, Isobel Cockerell, Marcelle Cockerell, Lesley Cockerell, Dorothy Hawes, Fred Hawes, Alan Welsh, Doreen Welsh, Winsome Harris, Beth Ashbv. GOOD SCRIBES, 5 3 32. Sydney Lester, Ruth Brown, Ora Parker, Doris Stanton, Patty Insull, Faith Harrington, Andy Chambers, Klvie Kerr, Frances Taylor, Vonnie Prazer, Doreen Cullimore, Norma Frazer, Daphne Dickie, Irene Mary Coates, Lila Hoatten,. DaY'id Guild, May Kelly, Patricia Cullimore, Peggy Taylor, Ultan Sullivan, Mary Parrish, Bert Kelso, Lesley Cockerell, Gwy nne Jones, Billy Clark, June Willcox, Alan Welsh, Dorothy Rickerby, Myra Jean Makin, Dorothy Hawes, Fred Hawes, Gladys Lawson, Brenda Payne, Jack Payne. Barbara Gibson. Enid Buckley, Zoe Bartlett, Joyce Bartlett, Irene Bartlett, ('oral Bartlett, Beth Ashby, Harold Williams.