Radio Review

Evening Star, Issue 20056, 22 December 1928, Page 16

Radio Review

Flashes from Everywhere.

I NAKED LIGHT DANGER; The danger •of taking a naked light ■ear the battery used for a radio set was shown by a very painful accident which occurred to a resident of Makarewa. Southland, states ah exchange. iWishing to see if the - battery,. which stood in; a dark corner, was sufficiently filled or correctly connected, the victim of the accident struck a (natch to inspect it. He was bending over the apparatus when the hydrogen from the battery exploded and splashed, some sulphuric acid in his. face. He experience a painful .burning sensation in his eyes, and when he groped his way to a light found that he was unable to see. Fearing that ho tifas blinded, be telephoned for help, but after about a Siarter of an hour hi's sight returned, ougH his eyes were still painful and bloodshot, so that they had to he bandaged and protected for some time.

THE GROWTH CF RADIO. The radio business, as a big business, has been going for about seven years. It is no small thing, therefore, to find that one manufacturer of high-class apparatus - has already turned out more than two million receivers; the,first million was completed in December, 1926, and . the second in October last. The firm is the Atwater Kent Co. In announcing this remarkable record, Mr Kent Said: “,Jt is naturally a source of gratification to me to feel that our company has reached the two-million mark in the production of radio receiving sets. I am doubly gratified by the fact that the second million sets have been made within, the short space of two years. Our first millionth set came out of the factory on December 3, 1926. Our, total of two millions to date has been produced in less than six years. This production, necessary in order to meet public demand, actually tells the story of radio more graphically than any words could tell it. Nothing else has ever so caught the imagination of the American people within such a short space of time, and brought to them a utility for practical advancement in .their social, cultural, business, professional, and recreational relationships. It interests me tremendously to consider our two millionth set in terms of the future of radio. Rapid as its strides have been, I believe that radio is still an infant with greater and wider fields of opportunity before it. The standardisation of receivers, the steady improvement in the quality of entertainment programmes, the daily expansion of the use of radio in commerce, industry, agriculture, and education, and the perfection of the allelectrid set give assurance that the present radio season will be the greatest in its history. Indeed, I ' anticipate that for the next six months the problem of the manufacture will be not to sell radio sets, , but to produce them in sufficient numbers to meet the public demand.' ’ With radio, just as with automobiles, the much-feared “ saturation point " has steadily receded, increasing public favour and more general use constantly leading to increased production. With simpler, more efficient sets, house-cur-rent power, better programmes, and reduced interference between stations, radio, in fact, seems just to be getting into its stride. A LEAD-IN HINT. A very_ common method of bringing the lead-in from the aerial into a room is to bore a hole in the sash of the window and run the wire, either insulated or bare, through it. In the latter case the wood of which the sash is composed will usually bo found to act as a sufficiently good insulator iu itself. _lt should bo remembered in boring the hole that this should always bo at a downward angle from the interior of the apartment, ,so that in rainy weather no moisture will he able to find its way through from the outside. Sometimes, however, objection to this method will bo made on the ground that it constitutes a permanent defacement. In such circumstances the difficulty can be overcome by making the glass of the window the dielectric of a condenser. Tuis can be very simply done. A sheet of tinfoil, of from 6in to 12in square, is cemented to the outside of the window, and the aerial lead connected with it. On the inside of the pane, and occupying a corresponding position to that of the other piece, should be cemented another sheet of similar size. From this one a connection is then made to the aerial terminal of the set. The sheets of foil now act as the plates, while the glass is the dielectric of a condenser in series with tbo aerial.; WEAKEST LINK. A wiring diagram may be regarded as a chain of components, ’ each of which is dependent on another. _ Which is the weakest link in the chain, and which should we try to avoid Tn all circuits? We oan eliminate as “ safe ” all components having positive “ through ’’ contacts, snch as coils, transformers,

NEW VALVES,

Have you taken particular notice of the new valves which have been placed on the market this new wireless season? You really ought to find time to make a careful study of the specifications of these new valves, you know. Then, when ..the time comes for you to buy your next new valve, you will know what type _ of valve will best satisfy your requirements.

One specially pleasing feature of the new valves is the increased amount of information given about them. Much of this information is conveyed in the type-name of the valve. For example, a valve marked P 315 is recognisable at once as a power valve of the twovolt class taking a filament current of .15 ampere. Some of the new valves have filament voltage and current etched on the glass bulb and, in addition, impedance and amplification factor. All this information may appear to be of little consequence to the non-tcchni-cal listener, but the fact remains that ’the more we understand of this valve information, the better results we shall .obtai.i from ur valves. ' In the screened-grid valve the chief innovation is the substitution of an upright type with a standard four-pin base and a terminal at the top for the horizontal type with three pins at one end and two at the other. A certain amount of improvement m valves is expected each season, but the 1928 improvements in existing types of valves, together with the introduction of the pentode, make us wonder if the present new wireless season will come to be looked upon as a valve season. if B •*. AND “0” VOLTAGES. TVhen “ B ” batteries are used to supply the plate current for a receiver, listeners are cautioned to watch the voltage of the batteries, and to discard them when the voltage of each forty-five volt block runs down to about thirty-four volts, or when that of each twenty-two and a-half block runs down to about seventeen volts. Fans who employ “B ” batteries therefore usually test them at regular intervals to determine whether the batteries are still good for further service. A matter of vital importance which is often overlooked, however, is that of pi iding a proper relation between the grid bias voltago and the plate voltage. It is geucrally known that, while " B ” batteries run down with usage, the “0” battery will 9 last for the entire lile of the battery without any appreciable loss of voltage. This means that when tbe “B batteries are > new, tho proper grid bias is being used for best results ; hut just as soon as the “ B ” battery voltage begins, to decrease, the grid bias voltage is greater than is needed for the lowered plate voltage. In such cades, if the grid bias voltage is reduced in proportion, as determined by consulting the tables showing the proper plate voltage grid bias voltage characteristics of the tube, the amplifying efficiency of the tube can he maintained at a high level in spits of lowered plate voltage from the “B” batteries.

■ * Henry " will b« pUued is answer say questions through this column relating to the fascinating hobby. Each •wrispcndent aw* d§a hie name and address (not necessarily, for publication), Newsy items will be welcomed.

NEW WAyE LENGTHS

BOON TO THE SICK

RADIO IN THE HOSPITAL,

and even condensers, which provide a continuous circuit tor A.C. current. Rheostats and potentiometers of the wire-wound type can be classed with those components giving positive continuity. This loaves us with grid leaks and anode resistance not of the wire-wound type, which, as they always provide imperfect contact, must surely be the weakest links. If, however, the makers of the leaks and resistance used in your set guarantee them to be accurate despite all temperature and climatic changes, or if your set has an anode-bend detector and no resistance, then the problem of the-weakest link remains unsolved. The weakest link is, in fact, the missing link!

FOR AMATEUR TRANSMITTERS

Consequent upon the Radio-Tele-graph Convention held at Washington last year, it is necessary to revise the frequencies, (wave lengths) in use for amateur transmitting stations. The allocation of the frequencies to operate under the new convention from January 1, 1929, are as under;— Ah amateurs: Bands 1,750 to 2,000 kilocycles (approx. 150 to 171.4 metres)', and 3,500 to 4,000 kilocycles (approx. 75 to 85.7 metres). in addition, those amateurs who have been given permission to operate on the band of 36 to 37 metres are to use the band 7,000 to 7,300 kilocycles (approx. 41.1 to 42.8 metres). Amateurs desiring the use of the higher frequencies, namely, 14,000 to 14,400 kilocycles (approx. 20.8 to 21.4 metres), 28,000 to 30,000 kilocycles (approx. 10 to 10.7 metres), and 56,000 to 60,000 kilocycles (approx. 5 to 5.35 metres), must make special application to district radio inspectors, supported by evidence of their qualifications for such special concession.

Few of the innovations at the Auckland hospital have proved more popular than the introduction of wireless, which is now fitted to most of the wards’, though - funds arc still required to complete the installation (says the Auckland ‘Sun’). There arc no loud speakers which would upset those patients unlit to be annoyed with any noise, but each bed lias its own headpieces, and patients are able to listen in whenever they feel inclined and there’is anything to listen to.

The set is permanently tuned in to IYA, though it is capable of being tuned in to any station that the ordinary set can pick up in Now Zealand.

The patients in their beds certainly get variety. Anything from musical and elocutionary recitals to horse racing provide the fare, ’interspersed with market reports, nows sessions, motor lectures, and physical culture addresses. In fact the patients in their enforced inactivities listen for hours on end, and many are the new trains of thought that are introduced to them.

In the big broadcasts, such as when the Southern Cross was winging her way to New Zealand, and Hooney was defending the reputation of the country in America, that hospital wireless has meant a great deal to hundreds of patients who were well enough to take a lively interest in the proceedings. .... Little imagination is required to realise the boon that this' system has been in the hospital, and. thousands of patients who have been inmates can speak of it in terms of appreciation. In addition to patients in tho hospital, the advent of wireless has been a boon to many hundreds of sick or elderly people in their homes, , filling in> tedious hours without strain as no library or'other diversion could have done .Both the patients and those responsible for attention to them have been by far the better for it.