RADIO NOTES.

Grey River Argus, 12 December 1928, Page 8

RADIO NOTES.

DYNAMIC SPEAKERS. (By “Sparks.”) Much has been said lately about the dynamic speaker, and people are apt to regard it as the ultimate in. loud speakers. They are also apt to get the impression that it is a recent addition to the world of radio. Such can scarcely be regarded as true, as about fifteen years ago, a dynamic unit wa.i used with a horn speaker. Now if wo can get an insight into the principle of the dynamic speaker, we are going to be better prepared to receive it when it appears on the market here We shall also have a better idea as to when and to where it can be' used with advantage. The correct name is “electro-dynamic,” which means n force generated by an electric current, so that the term could be applied to other electric devices in an appropriate manner. This gives us very little un derstanding as far as the speaker is concerned. To understand more fully let us compare it with the old type, which is a magnetic speaker. It has a permanent magnet, which slowly loses its strength, and in time will be weak to such an extent that its sensitivity will not be sufficient for proper operation. Now in the dynamic speaker an electro magnet field is set up, separate electrical energy being required to do this. This is supplied from a storage battery or from the house lighting system. In the dynamic speaker a moving coil actuates the diaphram and tho speaker cannot rattle, because the coil has movement, and cannot strike the poles of the magnet. The voice coil has no tone of its own by reason of the manner in which it is suspended; henc ' it tends to produce all notes impartially.

Different makes may have different methods of structure, but the principle remains in each case essentially the same.

The question many will ask is: “Can I use such a speaker with my set?” A radio engineer put the answer concisely when he said that it should not be used with a set that docs not have at least one power valve, and that it is advisable to confine its use to the newer types of radio sets. However, if you are in doubt consult a dealer who understands your set thoroughly. SUMMER AND STATIC. Many nights radio reception is impossible owing to the presence of sta tic. Those who own loop-operated sets are in elover, as the loop does not pick up as much static as an outside aerial. Many sets are not adpated to loop operation, but why worry? One nianu facturer of a very high class set says that the sets he builds are not adaptable because an inside aerial is much more efficient than a loop. He recommends a wire strung round the room, or placed under the carpet. Such an experiment is well worth trying and should give very pleasing results. NOTES AND JOTTINGS. The part being played by radio in every field of life is again made evi dent by a description of the equipment which is being taken down to Antarctica by Commander ,R. E. Byrd. The possibilities of radio will place this expedition in a more envious position than that of Captain Scott’s expedition. It makes us wonder what radio in its present state of advancement might have done for those gallant gentlemen. However, thanks to radio we hope to be able to follow this expedition right down to the South Pole and back again.

Many people are at a loss as to what the R. Code means. It is a code to denote the approximate strength of the signals received. This code varies slightly in meaning in different countries, but this interpretation is reliable:— Rl—Signals unreadable. R2—Readable with difficulty. R3 —Weak but readable. R4—Readable. R5 —Easily readable. R6 —Fairly strong. R 7—Strong. R8 —Very strong. R9-—Loud speaker strength.

The accumulator and its attendant discomforts have been the bugbear of the listener. The accumulator (or A Battery) requires charging, and this necessitates taking it along to the service station. This may mean a night with the radio off, or it may not he convenient to take it that day. All this can be done away wit.i by having a smr.il charger of your own. The saving in cost makes the investment one that cannot fail to appeal to anyone, and think of the absence of the usual Incom enienccs you formerly put up

Many set-builders, when buying parts, 'look to save by buying cheap components. The result is disappointing as far as performance goes. It pays to liuv good parts. They nut only last longer, but what is more important, do their work more efficiently. If the cheap parts were just as goou the manufacturers of high class pa its would be serving no good end, and ultimately would go out of business. . Christmas preparations are being made now. and presents are being planned. Why not look over the radio healer’s stocks? He may be able to suggest, something that fills the bill.