RADIO RECORD

Greymouth Evening Star, 12 January 1928, Page 8

RADIO RECORD

NOTES FOR LISTENERS-IN

(By

“Reception”)

A NEUTRALISED SET. CORRECT ADJUSTMENT NEEDED. If a set with neutralising means is to be operated to the best advantage, it is necessary that such neutralising device be properly adjusted. The method of neutralising a set with one stage of high-frequency amplification and some method of regeneration, is set out below, and will be found simple and effective. The object of the method is to find an adjustment of the neutralising condenser which will allow the greatest setting of the reaction control to be used without producing oscillation. To begin with, the neutralising condenser and the reaction control are both set at a minimum, and then the tuning condenser are both set so that the two tuned circuits are in step with each other. At these settings it will probably be found that the set is in a state of oscillation, and this state may be observed by touching the grid terminal or those plates of the tuning condenser connected to it, and listening for the click both on placing the finger in position and on withdrawing it. As it will possibly be found that the set will only oscillate when the two circuits are in tune, the presence of oscillation will indicate that they are in this state. The capacity of the neutralising condenser should now be gradually increased,, testing for oscillation as this is being done, and soon it will be observed that oscillation has ceased, and will not begin again even when the tuning dials are readjusted. The next step is to increase the reaction until the set commences to oscillate again, and then increase the neutralising condenser setting until the oscillations cease. Readjust the tuning condenser slightly, so as to make sure that the set is stable under these conditions. Carry on these operations until it is found that the setting of the neutralising condenser has been increased too much. When this state is reached it will be found that further increases in the capacity of the ’ neutralising condenser will not cause oscillations to cease, but will have the effect of making them stronger. Bring the setting of the neutralising condenser back to the point which is thought to be the correct adjustment, and it will be found if this is the correct point that when the two tuned circuits are in Step and. the set is brought to the verge of oscillation by the reaction control, a slight movement of the neutralising condenser in either direction will immediately cause oscillations to be set up. It is desirable to carry out the above operations at some point near the middle of the tuning range of the set. and, of course, it is not necessary to state that the whole set should be in the final state, with all the valves, etc., in the position which they will occupy immediately. In cas'es where two-volt or similar valves are used with standard screened coils or other types of intervalve coupling, it may be found that poor signals and other difficulties arise. These may be due to the fact that such couplings were designed primarily for six-volt valves. An increase of the plate voltage of the high-frequency stage may help, and it is often quite worth while increasing the grid-plate capacity of the highfrequency valves by connecting' an ordinary neutralising condenser between the grid and plate setting it about half in. The neutralising condensers are then adjusted in the usual manner.

CARE IN TUNING. TO OBTAIN GQOD RESULTS. Your familiarity, with your set and skill in tuning it- will play a big part in its proper operation and the securing of good result?. Most of the fac-tory-made sets to-day are of two types, tuned radio frequency with neutralised stages, or with; controlled oscillation. The former- is characteristic of neutrodynps. Ip. the neutrodyne sets we generally have three dials to tune to resonance before we hear a station. There is no whistle too guide us, as in the case of sets with controlled oscillation, the stations just coming in without any whistle or other means of knowing when we have a station. Therefore, we must turn the dials slowly. Otherwise, we %ill pass over stations. Oscillation when under proper control is an asset. The nearer we ar.e to the oscillation point without haying oscillation occur, the more sensitive our set and the more volume and distance we will get. But oscillation not under control is one of radio’s worst- conditions. Uncontrolled oscillation, if strong enough, makes our sets act as miniature transmitting •stations. Therefore, we interfere with our. neighbours and spoil their reception. •We can tell when our set is interfering with other- sets, as the whistles and squealing will be heard in the loudspeaker. Superheterodyne sets improperly handled will cause the same results. The tuning dials should be slowly and carefully turned, otherwise many stations will be passed over. Extreme care should be taken when tuning for distant stations, especially on sets with three tuning dials. As one goes down the scale the stations are sharper and great care will be necessary. The best way is- to first go over the scale and log the local stations. These will be loud and strong, and can be tuned in without much difficulty. Then search slpwiy for the long distance stations, and when each one of these is found, the dial readings, should be written down for ready reference at any time.

radio licenses.

FORTY THOUSAND REACHED. The prediction that- radio licenses would reach 40,000 by the end of the year has been verified. The figures for the weekly period ending January 6 are as follow: —

A SCIENTIFIC MARVEL.

PRODUCT OF LABORATORY. ..

A piece of steel floating unsupporc ed in the air is one of the scientific marvels produced in the radio laboratories of the Westinghouse Electric and Manufacturing Company. Only a thin# wire serving an an anchor to keep the steel from escaping is attached. With that exception the bar, which is 6 inches long, one-half inch wide, and one-half inch thick, has absolutely no visible means of support. The answer to the mystery is spelled by the word “magnetism.” Below the floating bar is a companion piece of steel of similar size and composition, and two bars, magnetised with like poles opposite, are held apart by the magnetic repulsion between them, which exceeds the force of gravity. The material used is cobalt steel alloyed with tungsten, which, according to Westinghouse engineers, forms the strongest permanent magnet known. The alloy was developed by Dr. P. 11. Brace, Westinghouse research engineer, after months of experimentation. & The new alloy is so highly magnetised that, when used as a horseshoe magnet, it will lift a bar .thirty times its own weight, representing a strength five times that of the ordinary magnet, according to Dr. Brace. Tn addition, the alloy clings tenaciously to its magnetic power, and will not lose it. Cobalt steel, such as is used, is relatively expensive. It will be used only wherp performance is worth more than price, as in delicate meters, fine phonographs and such precise machines as the Westinghouse oscillograph or “Osiso.” COMBATING INTERFERENCE. RADIATING RECEIVERS. As signals are so strong in the neighbourhood of IYA (Auckland), very little interference from radiating receiving valves is caused when listening to the local station.’ While IYA is working, distant stations are also comparatively free from interference, as the type of receiver which causes the worst trouble by radiating is seldoiri sufficiently selective to tune out the local station. Except for prohibiting certain types of circuit, so far practically nothing effective has been done by the New Zealand postal authorities to cope with this nuisance, although the portion of license fees retained by them is at present about £lO,OOO a year. The efforts of the postal authorities in Great Britain to trace listeners causing interference with radiating receivers, on’ the other hand, have had excellent results. A light motor-van has been fitted up with highly sensitive receiving equipment operated from a direction-find-ing aerial. The wireless van tours districts in which there is a complaint of interference, and whenever a radiating receiver is heard the direction from which the interference is comingcan be determined, and the van cruises round until the house in which the radiating receiver is installed is found. The van operates within a radius of 40 miles of London, and it is found that interference becomes worse as the distance from London increases. The reason for this is that as signals get weaker the use of reaction becomes more necessary for loud-speak-er reception, and the tendency for receivers to be allowed to oscillate increases also. The records of the wireless patrol show that on an average six radiating receivers are found each week. Of course the use of the wireless van causes most listeners to take special precautions not to allow their receivers to oscillate.

RADIO AS A PROFESSION. So sudden has been the march of broadcasting that in some avenues in which it opens up employment the demand for the suitable man has been greatly in excess of the supply. In manufacturing countries the technical staffs have proved adequate, for big research laboratories have turned out their quotas of trained-men who have found remunerative positions'in all parts of the globe. It is recognised that New Zealand must hold future opportunities for the highly-trained radio engineer, for it is not likely that only four stations will remain much longer to cater adequately for radio entertainment. In the radio trade, too, there are chances for the trained man, foi' proper servicing, a necessity in these days, requires. officers with a sound knowledge of theii’ job. Directing of stations gives another field to the specialist, for in the big centres of population the . station director holds a position that can be filled properly only by one of high attainments and special experience. Where radio yet lacks men of requisite capacity is in the announcing. Even America, foremost in the field of broadcasting, recognises this, though efforts have been made to provide training, in its fullest sense, for the men who have, day in and day out, to face the microphone and hold by their personality, vast, composite audiences. In radio anonuncing there is scope for the New Zealander, but he must have personality, persistence, and a broad education, if he is to handle successfully all the problems which occur on the spur of the moment. In these days when avenues of employment for youth are becoming more and more congested, few parents have given thought to the chances offered by broadcasting in its various branches. They are worth consideration, but under two strict conditions. The radio world of the future wants real, very real, technical men, and its requires in its administrative branches a high standard of literary ability. For the professional musician, too, the 20th. century marvel has improved employment and will continue to do so. Those with real musical talent will find its development financially worth while from the rewards that the microphone of the coming years will bring to them. THE PORTABLE SET. This type of set, comparatively new to us in New Zealand, has come into its own in England and to a lesser extent in America. By portable one means a set self-contained, weighing, complete with all batteries, in the neighbourhood of 30 to 401 b. These sets contain a loop aerial sometimes in the lid which is placed on top of the set. This latter scheme is ra-

ther more convenient, and does not mean moving the set when changing from one station to another, as it is necessary to move the loop to get its maximum directional effect. Portables under our conditions are set a difficult task, as they are expected to pick up the main Australian stations at speaker strength; no mean feat for so small a set where space is largely the determining factor and not efficiency. Portable sets are largely imported sets, where the number of alternative programmes within their range is much larger than there is in New Zealand. In choosing such a set, the buyer should express what he wants in the way of distant stations, so that the dealer may know just what his set is expected to do. A small non-spillable accumulator is a better proposition than a set of dry, but if weight is a big consideration, several C batteries in parallel give excellent results. The type of B battery fitted is necessarily of a smaller size, and must not be expected to give the same results in the way-of life as do the larger types used at Home. For convenience at the beach or in the car or camp, the portable holds it own, and the enthusiast on car or launch will use his battery equipment to work his portable set. All that is needed is a couple of long leads of flex as is used for house lighting, with battery clips mounted on .each end, care being taken to identify each wire if the flex is of the twin wire type, braided or twisted together. Once a set has accompanied one on a trip it always goes in the future, and this season should see the open-aii' New Zealander going afield with his lunch in one hand and a portable radio set in the other.

Receive Transing mitting Dealers Tl. Auckland 13,535 41 500 14,076 Wellington. 14,472 51 759 15,282 Christchurch 7,996 27 302 8,325 Dunedin 2,151, 17 174 2,342 — « ' ■ '■■■** Totals 38,154 136 1735 40,025 Weekly increases 787 1 14 802