RADIO RECORD

Greymouth Evening Star, 29 August 1929, Page 7

RADIO RECORD

NOTES FOR LISTENERS-IN

(By

"Reception”)

RADIO FREQUENCY POTENTIALS DISCARDING THE AERIAL Many people to-day have sets in their homes which do not strictly require the use of an aerial at all, but in most instances they have erected one, as an aerial terminal screw has been provided. They are generally not aware of any other source of radio frequency potential that will operate the set. Sets operating on the lighting circuit, as all up-to-date machines do, have two separate ground connections —one from the electric and the other from the regular ground system. These two grounds are at different radio frequency potentials, due to the fact that the radio waves induce a voltage in any length of metallic conductor; and doing away with the aerial simply consists of using this difference of radio frequency potential to operate the act instead of depending upon the voltage induced in a wire strung up for that purpose. It has been learned from experience that sometimes a ground wire, when conditions are just right (or just wrong, depending upon which way it is viewed), will actually reduce signal strength in a power-operated set with an aerial in use. This is due to the light line and the ground wire each having voltages developed in them that are out of phase, resulting in a “bucking” action. Since the lighting circuit cannot be eliminated because of power requirements, it is best to discard the ground wire altogether in such cases, if the user prefers to keep the aerial. By discarding the aerial altogether and connecting the ground lead to the aerial binding post the result will, in most cases, be just as good as before. Sometimes they are even improved markedly, but seldom are they any worse. This is better than discarding the “ground,” which is almost a necessity on account of the hum and attendant, noises because the ground lead is a simple installation compared with the aerial. The lighting circuit is not connected directly to the circuit of the A and B eliminator but there is always sufficient electrostatic capacity between the two circuits to allow the radio frequency current to pass. Whether or not static will be reduced by the use of the two grounds is a much mooted question, but at least the static will be no worse —if it is less, so much the better. Such a simple thing to try should not be overlooked by anyone owning an A.C. set. Even those with the older battery sets, if a B eliminator is in use, may try it. The experiment simply involves (disconnecting the aerial from the set and then changing the ground wire to the aerial binding post. Check the tuning to see if the volume and selectivity has been impaired or improved, and then decide between the two circuits.

MODERN BARTER An. amusing echo of the old-time bartering system reaches us from Hamilton, Ontario. A farmer came to the city wishing to trade-in an old set for one more up-to-date. He was attracted by the sight of a radio set exhibited in a sales window. Entering the store he made inquiries as to its virtues, etc., saying that he would like to tradein his old set. When told the cost of the transaction, however, he shook his head sorrowfully. “I haven’t that much in ready money,” he said regretfully. Suddenly a bright thought struck him, and he added: “But I’ve a line horse! I’ll trade you the horse and the l old set for your radio!” The salesman, recovering from his surprise, agreed that if the farmer would bring the horse along, he would see if business could be done. The farmer brought the horse, and the salesman pronounced himself satisfied, and the bargain was struck, an unusual hark-back to the old pioneer days of barter. A horse for a radio! SLIDE-RULE TUNING Slide-rule tuning, an innovation in radio receiving sets, together with several other important departures in radio design, is utilised for the first time in a new American set. The new simplified tuning device resembles a slide rule, and as the tiny knob moves across the precision scale, calibrated in kilocycles, accurate tuning is obtained. The tuning knob of this superautomatic selector operates over a full-visioned illuminated scale, with space provided at the top of the kilocycle figures for marking the exact positions of the stations. A vernier adjustment is obtained by turning the knob instead of running it across the scale. There are only two additional controls —the volume adjuster and the radio snap switch designed to put the set “on” or “off”. The tonal quality can be altered in accordance with the owner’s preference or the acoustics of the room. This is regulated at the factory for what is considered to be the best reproduction over the entire musical scale; however, by means of a simple adjustment the high notes can be reduced and the bass notes increased, or vice versa. CHOOSING A SET So many people have bought receivers on reputation or upon the assurance of others that intending purchasers would be well advised to give due thought to the following points when they are in search of new sets: —The prime consideration is quality of tone. ,A receiver is essentially a musical instrument, and lasting satisfaction can be had only when the tone is natural and pleasant, and this quality of tone can easily be judged by any person of discriminating ear. Reproduction that does not unduly emphasise the high or the very low notes and that gives natural quality to the speaking voice is satisfactory. This sort of reproduction is a substantial evidence, without need of further investigation, that the mechanism is of good quality. Selectivity is the next most desirable feature. If. the receiver can separate two local stations with only a slight movement of the tuning control, it possesses this feature. Sensitivity, or the ability to bring in many stations is the third factor, but it is not so important as selectivity. A sensitive set will bring in more stations, but selectivity is. needed for good tone quality without interference after they I are brought in.

THE ÜBIQUITOUS RADIO A CONSTANT LINK During a tour of the United States of America the outstanding fact that faced one all the time was the übiquitous radio, says a writer in a Home journal. It could not bo avoided anywhere —not even in one’s bedroom at homo hotels, for there were earphones. In crossing the Atlantic one was constantly reminded of the linking-up power of wireless. Each passenger was given a card which contained the terms for sending wireless messages anywhere. The third day out a wireless message came to me from England direct. On the notice-board on deck was the daily reminder that our ship was in constant touch with eight other ships, the names of which were given. It was no stretch of the imagination to think of each of these eight ships in constant touch with eight other ships, until the whole oceans and continents were lined up in a cobweb of radio design. Every morning there was awaiting us at our breakfast table the “Radio Bulletin,” which contained news gathered by the ship’s jadio from the four corners of the earth. On the fast American express trains was the unavoidable radio. Telegrams came and went all day long. The wireless operator on one train informed me that during one day the previous week fifty-six telegrams had passed through his hands, most of which were received for passengers. This wireless on trains is a great boon to busy business people, as it helps to facilitate appointments in particular. It has another purpose. There are many hoboes —knights of the open road —who still travel via “side-dooi’ Pulmans,” and who are frequently put off trains on which they are stealing rides. In the past these riders have been able to conceal themselves from the eye of the train crew. Now the passing train can send a. radio message to the train on which the poacher is riding freely and thus make his capture easy. <

VOICE OF LONDON “I am the voice of London, a voice lifted up in thankfulness for the return of His Majesty the King to his capital and his home.” These words were heard by wireless in a million homes in England recently—the 8.8.C.’s “surprise item.” “In the dark days of winter, on nights of fog and frost,” the Voice continued, “Londoners waited at the Palace gates—waited and watched and prayed. “Like the noise of many waters is London’s voice. 1 speak for all the Empire, and for our guests overseas. May God bless you, sir, and long preserve you.” The Voice grew faint as there swelled the sounds of the National Anthem —the Voice of London had spoken. ACCUMULATOR POINTS A two-volt battery is fully discharged when the voltage reading is 1.8. A four-volt battery is fully discharged when the voltage reading is 3.6, and a six-volt accumulator when the voltage is 5.4. The specific gravity of the cells in an accumulator newly received from the charging station should be about 1.2. When the specific gravity of any of its cells falls to 1.15 or thereabouts the accumulator requires recharging. If voltage or- hydrometer readings show that one cell in a four or sixvolt battery is showing reading widely different from its fellow or fellows, this fact should be pointed out when it is returned to thd charging station, so that it may receive special treatment when recharging. Apart from spilling oi- leakage, a. certain amount of the electrolyte in an accumulator is lost by gassing, so that a supply of distilled water should be kept on hand to make good this loss. Never let the little holes in the plug at the top of an accumulator become stopped up, as these play an important part in allowing the battery to “breathe”. Low tension batteries should be kept clean, cool and dry, and the terminals should be kept coated with petroleum jelly to prevent them from being attacked, by the acid. SOLDERING TIPS Cleanliness is a very vital factor in soldering; not only should the parts to be joined be clean, but also the flux. The purpose of flux is to prevent the formation of an oxide film on the metals to be joined, and also to. dissolve the fine oxide film which exists on the surface of metals, irrespective of how clean they may appear to be. It also assists the solder to “run” freely. Among the various fluxes which are commonly used for soldering are “killed spirits,” fluxite, resin and salammoniac. “Killed spirits” is probably the easiest and simplest to employ, but unfortunately it is liable to cause corrosion. Fluxite and resin are really the best, for they do not appear to have any corroding effect on copper. After heating the soldering iron, some means must be used to clean its tip. There are two methods. The iron can be inserted in a small quantity of killed spirits, but a better plan is to obtain a block of sal-ammoniac and rub the tip of the iron on this. You will find that this cleans the iron without filling the air with nauseating gas such as is given off when the tip of a hot iron is plunged into killed spirits. The soldering iron itself constitutes another pitfall for the unwary. Many constructors, even experienced ones, fail to grasp the advantages to be gained by the use of a soldering iron with a large copper bit. A common idea is that a very small bit will be much easier to use for delicate and finicky work than a large one. This is far from being the case.