RADIO AND ITS RECEIVERS

Sun (Auckland), Volume II, Issue 499, 31 October 1928, Page 16

RADIO AND ITS RECEIVERS

Conducted for THE SUN by

R. F. HAYCOCK.

New Radio Models AUTOMATIC TUNING New York Show Features RADIO WEEK was celebrated in New York recently, when the latest styles in sets and new inventions were developed at a radio show. New York being practically the nerve centre of the radio world, readers will be interested to know of some of the latest developments in radio. The following from the New York “Times” reviews what is happening in American wireless circles.

There will be two popular questions asked by visitors to the show and by those away from New York, who do not attend it. What is new in radio? And. If I buy a radio set this season, is there likely to be a new tube, a revolutionary development or television, to make the instrument look like an antique within 12 months? A year ago receiving sets reached what was termed the electrical era. The circuits and ' r acuum tubes were designed to operate in direct connection with the light socket, dispensing with all batteries. Millions of electric sets have been sold. The manufacturers in many cases overlooked precautions to offset the danger of current fluctuations. The result has been premature burning out of tubes and grid resistances. So much trouble was experienced with some of the sets that they were withdrawn from the market and improved models substituted. A year has, therefore, taught radio designers valuable lessons based upon practical experience. They contend that the 1928-9 receivers are designed so that no further trouble need be feared, although the current in the lighting lines may waver in voltage. The new models also tune sharper than some of the early receivers. Furthermore, the new sets are superior electrically and mechanically compared with most of the outfits of a year ago. They are easy to tune and because of their rigid construction are less likely to develop trouble. The chassis are of steel; the coils, condensers, tubes and wiring are protected in shielded metal compartments. NEW LOUD-SPEAKERS ARE POPULAR The popularity of the electro-dyna-mic loud-speaker seems destined to sweep the country, and there is every indication that it will be adopted by many broadcast listeners, with the peak of demand reached about Christmas time. One loud-speaker manufacturer is now advertising that his dynamic speaker is in 400,000 homes, so that the listeners get “ample volume with studio reaJism.” Some one has remarked that radio in the home is now just two things—music and a piece of furniture—and that the dynamic speaker is designed to satisfy the ear while fine radio cabinets please the eye. Realising this to be true, the manuiacturers have made their cabinets muen finer, more decorative, and in £ ases colour touches of brilliant do»L been added - There is no , at furniture and radio are to fin« «iv} y aJlied from now on, and that the will play a major part in oubH C ° f radio receiving sets. The r wants superior tonal quality P oduced by a radio circuit in a

piece of furniture harmonising with the rest of the room. Fine feathers are said to make fine birds, and now it is said that fine cabinets make fine radio sets. BEAUTY AND RADIO COMBINED The trend is witout a doubt toward the electric set and the dynamic loudspeaker. The third major trend is toward the combination radio-gramo-phone machine. All in all, the 1928-29 season will be known as the one that combined beauty and radio, at the same time introducing electrical and mechanical improvements that gave better tone quality. One manufacturer offers a definition for the new sets: “A radio receiver is an instrument which gives you your choice of all the broadcasting stations within range. When your receiver makes this selection quickly, brings in music and speech clearly, gives you no trouble at all —you have the best in radio.” What do they say about the dynamic speakers? “It achieves the realism engineers have SQUght for years,” contends one manufacturer. “Whether reproducing the human voice, a single instrument or the full orchestration of symphonic compositions, this unit defies descriptive power of mere words. It perfectly reproduces all frequencies in the audio spectrum, whioh literally means all frequencies within range of the human ear.” The merchandisers contend that the table model is in diminishing demand and that it remains on the market chiefly because of its economy, usually selling below 100 dollars. As the table model’s popularity fades the console’s gains. These instruments range in price from 125 dollars to 2,500 dollars, while the majority of sales are expected in the 300 dollar to 500 dollar class. Many of the table models selling under 100 dollars are equipped with metal cabinets. The radio-gramophone combination sell for about 500 dollars. AUTOMATIC TUNING There is evidence that automatic tuning will attract considerable attention this season at the radio shows. The new sets are designed so that they can be tuned as usual by a single drum-control adjustment, or favourite stations can be quickly located by merely pressing a small lever. The automatic operation is surprisingly simple. For example, if the operator desires to have WEAF on tap at a lever control, the station is tuned in as usual by the drum control, which is illuminated while in operation. Then a little cap on top of the lever, much the same in appearance as a key on a typewriter, is unscrewed several turns. Then the lever is pressed down and the cap tightened. This engages the

automatic device to operate on the 492-metre wave length. Thereafter, whenever that particular lever is pressed down, the drum control revolves to the point where WEAF is tuned in. There are nine levers in all, so that nine favourite stations can be awarded the levers. As this tuning system gains in popularity the star broadcasters may be classified among radio fans as “lever stations.” If a station fails to warrant a lever, the adjustment can be quickly made so that another station wins the lever. At the base of the levers is an illuminated panel upon which the call letters assigned to each lever can be printed# Automatic tuning, because of its convenience and its ability to simplify tuning, already has the earmarks of success. Women listeners laud the ease of operation it affords. When the housewives place their stamp of approval on a piece of radio apparatus it is generally successful. The women never liked the old horn loud-speaker with its goose-neck sticking up in the living room, so it lost favour. Women appealed for more decorative cabinets, and that is why they are in demand this season. They did not like acid batteries around the rugs. They asked for sets that could be attached to a light socket, like an electric toaster and a vacuum cleaner. That is what spurred the radio engineers to produce the all-electric receiving set. And now they have automatic tuning:

The screen-grid of UX222 tube is making its appearance in broadcast receivers this season. It is found in several of the new Freshman sets. The contention is that this tube gives seven times greater radio frequency amplitification than any other tub used for that purpose to-day. It is believed that more electric sets incorporating the UX-222 tube will be marketed next year. Television A survey conducted by “The New York Times” among leaders in the radio industry clearly indicates that television will be a vital part of radio in the future. 'However, to-day it is in the laboratory stage. Television developments will be gradual. There will be demonstrations this year to disclose advances being made by the large electrical laboratories, but this does not mean that the next day televisors- will be on the market for the public. How long will it be before radio set owners can look in as well as listen in? There may be televisors on the market late in 1929 that will i*eproduce motion pictures, probably 12 inches square, but three or four years will pass before the televisors are simplified; made foolproof; designed to throw large pictures on a screen; and to produce motion pictures, of athletic events and football games. The small picture will please the radio fan who cares more for seeing an image by*radio than the quality of it. In the early days of broadcasting tone quality was of little consequence. The main idea to get distant stations. But the majority of the public wanted tone quality and they did not buy radio sets until the concerts were reproduced with great fidelity. The same will be true of television. The first pictures will be small and hazy and marked by extraneous electrical impulses or blurred by statiq. When the public can see clearly the Harvard Stadium or Polo Grounds in entirety and watch the games at home on a screen millions of sets will be sold. But the millions will feel an expenditure of more than £2O will not be warranted to pick up an indistinct picture several inches square. After the first television sets appear the development will no doubt te l-apid. Five years after the pioneers buy televisors the radio scenes ought to reach a fair state of perfection if the progress of broadcasting can be taken as a parallel. In the meantime there should be no hesitancy in buying 1928-29 receivers for fear that television will make them obsolete. Those who have witnessed the television experiments in the large laboratories are convinced that television, practical and simplified sufficiently for the home, is not just around the corner, but it is not so far away—the research engineers and large laboratories are in keen competition with each othei'. They see the goal ahead and all are eager to be the first to reach it.

SOUTHERN CROSS BROADCAST The staff of Station 2BL again earned unstinted praise from listeners for their work in connection with the return flight of the “Southern Cross” from New Zealand. Letters, telegrams, and hundreds of telephone calls reached the New South Wales Broadcasting Company’s offices, saying how much the work of the announcers and the engineering staff was appreciated. It was surprising to learn the number of listeners who remained at their sets right through until the arrival of the flyers in the early hours of Sunday morning. Another successful phase of the flight was the relay of 2BL by the New Zealand stations. Intense interest was taken in the flight by listeners in the adjoining Dominion, and just before 2BL closed down, the New Zealand stations sent through a message of thanks and stated that the relay was about the most successful which they had yet carried from Australia. Throughout the whole proceedings the rebroadcasting was quite as good as direct reception. At the Richmond Airdrome, the 2BL staff worked under great difficulties, owing to the tremendous crowd which unexpectedly attended to welcome the flyers. When the doors of the hangar were thrown open to let the broadcasting staff in to get a message from the flyers, the crowd rushed in. Half a dozen policemen saw the difficulties which the 2BL men were working under, and three of them lifted the broadcasting lines up over their heads while another three policemen formed a cordon round the announcer and the airmen. Thus, thanks to the foresight, to the literal arms of the law, tho public had an opportunity of hearing the returned airmen broadcast their messages. TELEVISION RECEIVER A television receiver kit for amateurs who wish to construct their own sets and experiment with ethereal images has been put on the market. The outfit consists of a scanning disk, special driving motor and control rheostat for speed adjustment, resistance amplifier unit, neon lamp, and motor bushing for mounting the scanning disk on the motor shaft. These parts when assembled form a unit which can be plugged into the detector tube output of the ordinary broadcast receiver or short-wave set. The disk is said to be the result of considerable experimentation and combines lightness, rigidity, and the required mechanical accuracy for good recep-

tion. A new combination disk comprises three sets of spiral holes for reception of images of 24, 36 and 48 lines each by adjusting the neon tuba before the series of holes desired. THEORY OF FADING Before fading can be eliminated considerable must be added to knowledge of the upper atmosphere and the cause of absorption, according to experts of the Naval Research Laboratories at Bellevue. Before the engineer can devise ways , and means to prevent or counteract fading the scientist must find . the : cause thereof. Upon this basis have experiments been going forward. Now there has been formed a quantitative theory of the propagation of * all radio waves, long or short; a theory i which is considered sufficiently power- ; ful and comprehensive to explain many known radio phenomena and to predict new ones which are also receiving : substantiation. : The theory explains fading and direc- : tion errors and gives a clue to the cure of these troubles. A detail of s it is that fading is not the same in all wave lengths, and that there is an i almost complete absence of fading on t one wave length when it is particu--5 larly bad on another. Moreover, the 5 theory permits of advance calculation of fading.

TRANSFORMER FAULTS Among - the more . common failures in components other than valves and batteries, burn-outs, or breaks in transformer windings, are probably the most frequently encountered. Owing to the large number of turns of wire which must be placed on an intervalve transformer it is essential, unless the transformer is to be very bulky, that the wire used should be extremely fine. As a result, most modern audio frequency transformers are wound with wire considerably finer than a human hair. Although this wire should be capable of carrying* the full current impressed on it in a normally operated receiver, weaknesses which cannot always be avoided in the manufacture of the wire occasionally occur, and a slight overload will cause a burn-out or break of the winding at these points. Transformer winding breaks are frequently difficult to detect in their early stages, because, except in the case of a veijy heavy overload, the winding does not part so suddenly that the circuit is completely interrupted. They usually develop over several weeks, or months, in which time reception is first affected by sudden unaccountable fades, and frequent interruption by scratching and frying noises. Later, as the break progresses, the fading of signals becomes more frequent and complete, and finally, if the transformer is not replaced or repaired, the set will cease to operate. There is really no certain method of repairing a burned-out transformer short of rewinding it —a process beyond the powers of most listeners. In some cases, a more or less complete repair can be made by connecting the ends of the damaged winding momentarily across a hightension battery and applying about 40 volts to it. The effectiveness of this process depends on the fact that an electric arc is sometimes formed at the point of the break. If the experiment is successful, this arc melts the wire at the point of break and fuses the broken ends together. In most cases, however, it merely aggravates the break, or is altogether ineffective. Undoubtedly the most effective means of restoring the receiver to working order is to replace the damaged transformer with a new one

A transformer with one winding burned out can be used in an emergency as a choke coupling, and in this capacity, it will give indefinite service, although in a great many cases, a certain amount of distortion may occur. Comparatively little reconnection of the set is necessary to use the transformer as a choke. The transformer must first be tested to ascertain which winding has been damaged. This can be done by testing first the primary, and then the secondary winding for continuity by means of a small battery and a pair of head telephones. The. test consists of including the battery, telephones, and first the primary and then the secondary windings of the transformer in a circuit. If the transformer winding under test is sound a crackling will, be beard in the telephones, as the circuit is completed and broken. A break is a winding. . however, will prevent the current from the battery passing through the telephones, and only a very faint sound will be heard on making the circuit. When the damaged winding has been found, it should be marked, and the transformer placed in the receiver so that the undamaged winding may be connected between the plate and the high-tension battery of the first of the two valves it couples together. This, of course, is the ordinary position for the primary winding in a transformer coupled

amplifier. The plate of the first valve is also connected to a mica fixed condenser having a capacity of about .05 mfds. The second terminal of this condenser is connected to the grid of the second valve. A grid leak having a resistance of about .5 megohms is connected from the grid f the second valve to the filament circuit of the valve. In some cases it will be found that the receiver will work effectively with this leak connected to the negative side of the filament. In others, however, it may be found necessary to connect the grid leak to the positive side of the filament. A grid leak of considerably higher value will probably be found necessary if this is done. AMMAOIK DATA SOUGHT . Effects of extreme cold weather over long perit/ds upon radio equipment will be part of the data that the Byrd Antarctic expedition will gather. In, making preparations, engineers representing Commander Byrd and the Bakelite Corporation have considered the possible effects of temperatures from 50 to 75 degrees below zero on j panels and other parts of radio equipment. Since no laboratory test could compare with the actual experience in the South Pole region for months at a time, engineers say, the findings of thisi expedition may prove of definite scientific value..