CRYSTAL SETS.

Press, Volume LXVII, Issue 20274, 27 June 1931, Page 9

CRYSTAL SETS.

GETTING BEST RESULTS. SIMPLE AND INEXPENSIVE. The crystal receiving set embodies a secret of Nature so cleverly concealed that not even the- most learned scientist can explain exactly how it works —how it detects. Yet the crystal set is so cheap that its cost is less than the license fee. In spite of the fact that nobody Knows how a crystal works, there are one or two ways of making it work better. A crystal set detects by means of a crystal, generally galena, which makes contact with what lias been called for seme unknown reason "a catswhisker." The catswhisker consists-in reality of a piece of fine wire. Almost any piece of fine wire will do. Some arc better than others, not because they detect better, but because they do not deteriorate. Copper wire makes the worst catswhisker. It oxidises in a few days. Gold wire makes the best "whisker." Suitable gold wire neatly spiralled may be obtained for a few pence. Even gold tarnishes aftot some months. For that reason it is advisable to snip off the tip from time to time,. leaving a fresh point exposed. Even with gold wire, it is not good to leave the crystal permanently set. Chemicals in galena act on gold, causing it to oxidise. When the set is not in use the "whisker should be separated from the crystal.. All crystals except those so-called permanent ones, have facilities adjustment. The crystal itself needs no attention. It will work after the most brutal treatment. As a new crystal costs only sixpence or so it is wise to make a change every few years if the old one. seems unsatisfactory. Some people have had crystals in use for five years or more without any trouble at all. It is unwise to chip the crystal. -Generally the result is worse than before. Care of- Headphones. Headphones used with crystal sets require a little care if best results are to be obtained. . Avoid dropping. them. Such ill-treatment causes the small magnets inside, upon which reception depends, to lose their strength. The connecting leads should not be allowed to g«st into tangles. If they do get into kinks, the best way to disentangle them is to twist the headset one >vay or the other. Do not pull hard. Kinks and hard pulls are apt to break the fine wires inside. When that happens one moment reception is good, the next it is very faint. The cure is a new set of cords. Once bought, the upkeep of a crystal -set is only a few fence a year, provided

care is taken. All the power to operate the set is provided by the broadcast authorities, via their aerial. The better the listener's aerial the more he will be able to avail himself of something for nothing—so unusual these days. Next to a good aerial a good earth is the next desirable point. Both are essential for good results, Bods hammered into the garden to provide an earth should be suspect. In wet weather they may work well—in dry they ma not be earths a f all. The best and most reliable earth is a connexion to a rising water-pipe. Special clips may be bought for about sixpence to fit various size- of pipes. The sizes of water-pipe commonly used are half-inch, three-quar-ter inch, and one inch. Three-quarter inch is the commonest. The measurement is of the bore, not the outside of the pipe. The earth lead aliould be kept under ten feet long' if possible. Selectivity on a crystal E3t is never vcr~ good. A short aerial assists at the expense of loudness. Alterations inside the set may be possib If so it is better to tap off the crystal circuit about />ne-third of the way above the earth connexion. This also increases signal strength several hundred per cent. Any radio dealer can make the' alteration to suitable sets ! n a few moments. BROADCASTING SERVICE. STATEMENT BY POSTMASTER. GENERAL. ' * "Anyone who owns a wireless set to-day has an instrument of enjoyment," said the Hon. J. B. Donald, Postmaster-General, in officially opening the recent radio exhibition in Wellington. He. advised prospective buyers to purchase now. and not wait. To dglay buying was to forfeit a good deal of pleasure. Wireless was a good friend, particularly in times of depression. He stated that the broad question of control and ownership of major stations was under consideration by Cabinet, but had not been finalised, and lie not prepared at the moment to make a definite announcement. He stated, however, that he had approved of a proposal that a sponsored programme in a modified should be allowed in the ease of £ class stations. , When the new regulations were gazetted listeners would be more satisfied than they were to-day, said' the Minister. He emphasised that the Government had no reason to find fault with the present broadcasting company, which had done very well indeed in the circumstances. Listeners, however, were demanding more than they were getting now,. and as they paid the piper they were entitled to consideration.