THE RADIO WORLD

Southland Times, Issue 20081, 19 January 1927, Page 9

THE RADIO WORLD

NEWS AND NOTES

(By

“Reflex.”)

As the result of investigations among statistics, it is estimated that at present there are nearly fifteen million radio sets in use throughout the globe, and about half of these are located in the North American continent. Were every important transmitting plant able to be tuned in by a set owner, he would have a choice of over 900 stations that are now on the air. Again, more than half of these would be heard from North America.

What are the oldest wireless waves we know? The answer comes from Harvard University, where Dr. Shapley, the Director of Harvard Observatory and his assistant Miss Ames are at present studying the light waves from spiral nebulae in the depths of space beyond the constellation Virgo. Using an instrument called the blink microscope they have been able to make an estimate, based upon the fluctuations of certain Cepheid Variables, of the age of these light waves. Their estimate is ten million years! These then are the oldest ether waves we know and they have suffered no change. Surely the Mind that conceived the Ether of Space can read its record.

To the layman one of the most impressive things about wireless is the enormous speed at which the messages travel. One may converse with a wireless man in New York or London without being conscious of any time interval between transmission and reception. We have not, as it were, to wait for our message to get across and for the reply to come back. Practically it is instantaneous. Actually there is a time interval but as it amounts to only one-fifteenth of a second in going half-way round the world, we do not notice it. If, however, we could open up communication with Mars, the time taken in transit of messages would be appreciable, as it would amount to nearly 31 minutes when Mars is nearest to the earth. During that inter-

val our messages would exist in the form of a record committed to and preserved by the ether of space.

Listeners should be careful not to drop their headphones. The jar weakens the magneto, even if the headphones do not break through the fall. Headphones should be handled with care, and they will retain their qualities for many years. A pair of headphones were shown recently, which, when tested, were as good as new after five years’ service. Another thing to be avoided is the connecting of the headphones with their polarity reversed. This is ruinous to the magnets. The red or plus cord of the headphones should be connected with the plus of the B battery, inside the jack. With a crystal set this precaution is unnecessary.

Broadcasting sen-ices in Victoria are likely to be improved at an early date by the erection of several relaying stations in country districts. The stations of which there will probably be three, will be operated in conjunction with the Melbourne station 3LO. Relay broadcasting was first developed in Great Britain by the British Broadcasting Co., and a broadcasting system which is admitted to be the finest in the world was developed. Briefly, it prorides for the erection in selected centres situated some distance from the main broadcasting stations of minor stations, which are supplied with programmes from the main stations over land telephone lines. The advantages of the system are two-fold. In the first place a listener in a district served with a relaying station, even though it be some distance from a centre at which talented artists are available, can obtain high-quality concerts from a local station, and he can, therefore, use insensitive and inexpensive apparatus to obtain a first-class service. The second advantage of the system is that the fading and other interference, such as atmospherics, is overcome. The power of the new Victorian stations will in each instance be about half that of 3LO.

THE ACCUMULATOR

Thousands of accumulators must be mined every year by bad charging and faulty electrolyte. Of course, those who send their shells to be charged at a charging station, where they can have professional attention, are quite safe, but what about those amateurs who charge their own ? Perhaps a few hints to those home chargers will not be amiss. One of the most important points is the mixing of the sulphuric acid which is to be used in the accumulator. If the greatest care is not taken, if certain necessary precautions are overlooked, or if the correct specific gravity is not obtained, it is quite likely that a perfectly good accumulator will be hopelessly ruined. Some people, when testing an accumulator which is on charge, use only the voltmeter; others only trouble to test with the hydrometer. There is only one correct way to test the accumulator, that is by both the voltmeter and the hydrometer. Merely taking a reading of the density of the acid in the cell will not suffice, as if the water has evaporated to any extent, or the acid has not been correctly mixed, the hydrometer will not give a reading which can be relied upon. Perhaps this point has troubled some amateur chargers before now, so it may be well to give an instance. We will suppose that a battery has been on charge for a considerable time, and is giving a voltage of from 2.5 to 2.6 per cell, the electrolyte gassing freely. If the hydrometer reading gives a specific gravity of only 1220, we may take it for granted that the electrolyte is not correct. frequently, home chargers find that their accumulator will not function properly after a few charges. This may be due to a short circuit between the plates, caused through the following circumstances:—lt sometimes happens that sufficient care is not taken when the proportions of acid and water are measured. If these proportions are incorrect there is a tendency for the paste in the plates to loosen and drop out, so causing a short between two plates. Again, in an accumulator in which the proportion of water and acid is not correct, the risk of sulphating is considerably increased. Nov.- we come to an important point. One amateur who, through carelessness in mixing the acid, nearlylost his sight. So, a word of warning. Be particularly careful that the acid is poured into the water. Do not adopt the opposite procedure. V hen sulphuric acid and water are mixed together a great deal of heat is given off. It naturally follows that if a little water is added to a lot of acid the amount of heat generated will be greater. This heat can, in fact, be so intense as to cause the acid to boil almost instantaneously, with the possible result that the person doing the mixing may receive some splashes of acid in the face or eyes, as happened to the amateur mentioned above. Let it be repeated, therefore, that the only safe way of carrying out the mixing is to pour the acid into the water. The approximate proportions are one part of acid to four parts of water. Don’t forget, too, that only distilled water should be used for this purpose. When the mixture has been allowed to cool off to its normal temperature, it may be found that the density is not correct. Thus may be remedied by the addition of very small quantities of water or acid as required. In conclusion, it is an excellent thing to empty the battery now and again, and give each cell a good cleaning out, with cold water. The time that is occupied by this procedure is not wasted.