ON ALL WAVELENGTHS

Evening Star, Issue 20468, 26 April 1930, Page 8

ON ALL WAVELENGTHS

By

THE LICENSE FIGURES. Figures supplied by the Post and Telegraph Department show that the total number of licenses issued in the dominion as at March 31, 1930, was 52,407, an increase of nearly 8,000 oyer the licenses at the corresponding period last year, when the total amounted to 44,810. Of these latter 194 were free licenses, while this year the number of free licenses jumped to 215. At March 31 1929, Otago claimed 3,136 of , the total issue, including 29 free licenses, while this year our figures have gone up to 4,867. The free licenses in Otago did not increase during the year, and this seems strange, one is tempted to sa £i when it is considered that this is a Scotch province. SCREENED GRIDS AND THE TUNED ANODE. An advantage of the shielded highfrequency tube is that a plain tunedanode circuit may bo employed with excellent results as far as amplification and better selectivity go than when the whole coil is included in the plate circuit: This does not alter the principle of the circuit. But it has one drawback It provides a connection between the grid of the detector and the lowfrequency valves, with the result that low-frequency howling or even motorboating is particularly liable to occur. A' resistance-capacity filter may,, of course, be included in the high-tension wire to the anode circuit, and will prevent howling and distortion. The cir-

cuit is, nevertheless, a dangerous one, although it gives excellent in many instances, and tho question arises regarding how an improvement may be effected. ~ The obvious answer to the question would be by preventing a direct connection between tho anode circuit of the shielded valve and the detector circuit. This may bo accomplished by employing a high-frequency transformer coupling instead of the tuned From the connections given in the diagram it will bo ctear that low-rre-queney reaction is eliminated by this means, as the grid is coupled to the anode circuit .by a transformer which transmits only high-frequency oscillaA transformer is, unfortunately, a rather more expensive component than a tuned-anode coil, and unless it is pro-

perly constructed the performance may not .bo quite so good. The selectivity and magnification- may,_ however, be made almost identical with that to bo obtained from a suitably tapped anode coil. Theoretically a tapped anode coil and a transformer give identical results, but in practice tho transformer must bo just a little inferior, there is very little in it when the xransformer is a good one.

NEW CONDENSER MICROPHONE, A new typo of condenser microphone which is claimed to give a better quality of transmission has been designed by the chief engineer of station \VBAL, Baltimore,' America. The instrument is the product of three years of exhave been installed at tho station to permit the operation of two of these condenser microphones in each studio and in the announcer s booths. The microphones are said to be different from the usual type of condenser instrument in use to-day. They employ the push-pull principle ot operation. m that the vibrating diaphragm is provided with two fixed plates, one of which'is perforated in a special manner to permit the passage of sound wflvc energy to strike tho diupliragni and cause it to vibrate in accordance with the sound it receives. No polarising voltage or audio amplifiers are used with the instrument. JLhe usual polarising and amplifying system is replaced with a simple radio-frequency system giving complete freedom from distortion, and thus ensuring that the electrical output of tho microphone is exactly in accordance with the vibration of the diaphragm. Iho use of tho instrument results in a silent background for the reproduction of music. ‘ RADIO HANDBOOK ANNUAL.’ A greatly enlarged edition of ‘ Radio Handbook Annual * has been published this year, and some 120 pages have been devoted to various topics concerning wireless. Tho writer has received a copy from the publishers, and this contains no less than forty-five articles, ranging from a general talk about radio to tho construction of big and small sets and some of the components. At the end of tho issue is a complete list of broadcast and short-wave stations which may be heard in New Zealand, while a verv handy time chart is given free with the annual. All the constructional articles are accompanied by diagrams which make it easier for the enthusiast to follow.

NOTES AND COMMENTS

ARLIAMENTARY DEBATES. PROPOSED BROADCASTS. It is announced in an Australian magazine that a proposal for the establishment of a high-powered broadcasting station at Canberra has been submitted to the Prime-Minister (Mr Scullin) and other Ministers by Mr J. C. Eldridge, M.H.R. Among the uses to which Mr Eldridge believes the station could adapt itself is the broadcasting of parliamentary debates and Ministerial pronouncements. His letter to Mr Scullin reads; “ As the Federal capital city of the Commonwealth, Canberra is, in my opinion, entitled to have erected in it by the Federal Government a high power broadcasting station, there are many reasons for this, including the following:— “ Tho numerous applications for broadcasting wave-lengths greatly exceed the number of stations that can be placed on the air without intciference. it would he a public calamity if, through delay, the air were closed to tho Federal Parliament. If the Federal Parliament means anything'in the lives of the people of the Common- ■ Wealth it should have its secured position on the air and to be able to use in tho interests of the people of Australia, the most modern means of communication yet devised. I, therefore, strongly recommend that without delay ■ the Federal Government proceeded to erect at Canberra a high power broadcasting station to embrace tho following • « 1. Tho Federal station should be constructed to operate on both long and short waves, as follows: — (a) Long waves for Commonwealth, New Zealand, and Oceanic communications. (b) Short waves for world communications. “ 2. The scope of operation of the Federal station would bo as follows ; (a) Broadcasting Ministerial pro-

nouncements. (b) Broadcasting parliamentary debates. . ~ (c) Morse communications; Government traffic. . (d) Broadcasting entertainment; relays and local broadcasting. “3. Ministerial broadcasting. Each Minister could have on . his desk a microphone, through which he could .broadcast from time to time important pronouncements emanating from “is department, essential or desirable to bo broadcast in the public interest. “4. Parliamentary broadcasting; Parliament could bo furnished with a series of microphones through which its most important debates could be broadcast to the public throughout the Commonwealth. , “ parliamentary news .could also be broadcast indicating the precedence of parliamentary business. “ The Federal station would also be used for publicity purposes by the various Government departments, such as: , ■ (a) Calling for tenders. (b) Advertising results of tenders. (c) Publishing advico re hea th matters and epidemics from Health Department. (d) Advice to farmers. (e) Taxation pronouncements, etc., etc. “5. Government traffic : A system of Government communications could be worked out along lines I am Prepared to submit in detail if desired Broadcasting is one of the cheapest, q uic h est, and most flexible means of communication, which has remained Practically undeveloped under the L .M.G. administration. “ World broadcasts, could bo made to advertise Australia and its products. “G. Broadcasting entertainment: Broadcasting relays from the principal A and B stations throughout the Commonwealth would be done mainly in the evenings, together with local broadcasts.

RADIO’S TEN COMMANDMENTS. Never take excessive shekels with you but only a certain abundance, for verily 1 say unto you, a radio store and a super-salesman likens in enticement unto an eager house agent. _ , And upon the coming to the wireless shop look not into the window thereof, for the prices inside shall exceed those in the by half, eleven exceed themselves twice over. Let not the radio salesman awe thee, for verily might he have been but a butcher boy himself a short time hack. If ye be but a humble novice and have wish to invest in a valve set, let the expert think you want a crystal set, and in your artfulness you will see a range of sets from tho lowest unto the highest order, and learn much thereof. And decide not at one store, for ot wireless shops there are many score, so great in number that they liken unto the sands of the seashore. Before deciding on thy purchase entreat the salesman to give unto you a demonstration, and if he refuseth saying that it is inconvenient, take up thy hat and walk, and then, before you have walketh but two paces, he will have suddenly found it convenient —and there is tho moral thereof. Hush not into the purchase, but rather liken thyself unto a cable tram and go slow. Let not a cabinet of much polish or a panel of complicated controls dazzle tbeo and captivate thy mind, for it might be a wolf in sheep’s clothing. Hearken not unto thy neighbour lest he not bo a genuine radiojtc, but see tho news agent and invest in a regular f-opy of tho ‘ Listener In.’ If ye desire to understand radio and bo possessed of much wealth, follow the Radio Construction Course which now nppenreth in the ‘ Listener In,’ and benefit thereby, for verily radio is not dead, nor yet sloepeth, but is travelling hither and thither about the land like a raging lion, devouring all with whom it come in contact. —‘Listener In.’

A FEW MORE TIPS. Every receiving set employing an outdoor aerial should have a good lightning arrester: An interesting case which recently came to tho notice of the writer should help others to solve a problem. A receiving Bet owner complained that his set refused to function. The tubes lighted, and batteries were quite all right when tested. There was no broken connection, and other parts of tho set were in perfect order. Finally the fault was traced to tho lightning arrester, which had done its work at some time and shorted the aerial through to the ground. The fault was soon rectified. When loud speakers are arranged in series with one another, it is very easy to short one of them by means of an ordinary on-of filament switch. A great many failures to get good reproduction arises from carelessness with the grid-bias battery or its leads. A pound of plasticine is a very useful compound to any wireless man. A few of the uses it may be put to should bo enumerated. With aerial coupling it is sometimes desired to support a coil at a particular angle, and at a given height. A small piece of plasticine ca’n easily be shaped to form the necessary support. Another small piece will temporarily fasten two lengths of wire in the desired position when they show a tendency to tangle or to cause a short circuit by touching. In short wave work, when tube holders are dispensed with to give increased efficiency, a tube may be securely suported upside down when its bulb is pressed into a piece of plasticine. The use of the correct types of tubes is one of the secrets of successful distortionless reception. One of the causes of scratching and scraping noises in the set is when a primary winding of a low-frequency transformer or a low-frequency choke is burnt out.

WIRELESS WIT. A headline in a daily paper reads: ‘Are You Keeping a Log?’—No, but we’re going to get one to use on tho person who oscillates next door. • • * « A .lady is to tell us over the air about ‘ Woman and the _ Law.’ All that is known at present is that tho one lays the other down. • ft . « (» First Enthusiast: “Why have you slung your aerial so low?” Second Ditto: “ I try to get tho low waves.” ■ • 9 * • There was once a wife who, hearing her husband talk a good deal about fading, always drew the curtains when the sun shone on the radio set. A DX COLUMN. It lias been suggested to the writer that a DX column should be started. What do readers think of the idea? Tho object of the column would be to enable listeners hearing stations whose identity they did not know to ask other listeners through the ‘ Star ’ radio columns where tho station is situated. The following week anyone who had identified the station could drop a line to the writer who would be only too pleased to let the inquirer know what station he had heard. To set the ball rolling, one listener states that he listened to a station - « about 31 metres on Saturday last about 9.20 p.m. Static was very bad, and be could - ot get any announcements. Does anyone know what station this would be?

ANTARCTIC APPRECIATION. That the programmes of tJio Sydney broadcasting stations have proved acceptable to the explorers in the Antarctic was revealed by a letter to the A.B.C. in Sydney. Air A. W. Parkins, one of Admiral Byrd’s men on the supply ship Eleanor Boling, wrote: “It has been a great pleasure and reliever of long hours to listen to the line broadcasts you have sent from your well-managed stations. The whole ship’s company shares this view. . . . I’ve had the pleasure of meeting several Australian citizens, mostly from Sydney. With any luck, I’ll visit your Commonwealth some day.” A “SHOCKING” TIME. Housewives in Scotland and the north can expect a “shocking” time when the giant high-powered radio stations are opened at Moorside Edge, near Huddersfield, and Larbct, raidway between Edinburgh, and Glasgow next year. They may find it difficult to pick up metal kitchen utensils without getting mysterious electric shocks from the ether. This has been the experience in the vicinity of the Brookmans Park station, and as tho new stations for Scotland : .d _ tho north are to be on the same basis ns tha at Brookmans Park the same effects may be expected. These shocks are not sufficiently strong to do any harm,'and aro only received in certain circumstances ._ 'For instance, housewives living in tho vicinity of tho station who left a. bucket or a rubber mat in the kitchen felt a tingliijg sensation on picking it up again some time later. The bucket picks up electrical energy from the ether. But this only happens if tho metal object (the bucket in this case) is insulated from the earth, as by the board or rubber mat. A 8.8. C. engineer who was at one time employed at tho old London station on the roof of a London store states that it was possible for anyone in the building to hear broadcast programmes merely by wearing a pair of headphones and touching the headphone wires against one of the hot water radiators!

The Post Office commercial accounts for tho financial 3 T enr ended March, 1929, show that the cash receipts for w ; -eless receiving licenses 'stalled £1,358,187. The 12} per cent, credited to the post office for expenses of management and other costs absorbed £178,686, leavin'- a balance of £.1,179,501. The sum paid to the British Broadcasting Corporation was £88',616, leaving a balance accruing to the Exchequer of £291,885, an increase of £47,000 during the year.

STRAY SPARKS. Listeners everywhere are still complaining of the silence in the diunci sessions. All seem to appreciate the music, but they become very annoyed when they have to sit for a few minutes waiting for tho next record to be pla * ed - . * . , Many times lately the writer has been asked when the company is going to extend its Sunday hours to 10 p.m. Tho writer is himself waiting for the question to be answered. • * • • A private transmitter has commenced operating in the Waikato district. It is IZH, operated by G. S. Anchor’s Radio House, Hamilton. It has an output of 30 watts, and opera*-s on 630 kilocycles or 479 metres. _ At the present time the transmissions are irregular. * * * • In America recently statistics proved that in selecting their radio programmes 75 per cent, of listeners referred to their newspapers, 20 per cent, chose by what they heard other listeners recommend, 4 per cent, merely turn their dials and take what comes, and 1 per cent, listen regularly to one favourite station. • * • « With a power of fifty watts and using a wave length, of 285 metres, 2XF Palmerston North is regularly on the air from 6.15 to 9 on Wednesday evening, and from 7 to 9 ou Sundays. » * • • At tho Victorian Radio Institute Radio Exhibition recently there was an amateur announcer’s competition. Each evening a number of aspirants read their set pieces into a microphone on tho stage. Whilst the visitors to the exhibition heard their actual voices, the judges sat in an upstairs room and noted the transmissions. Marks were allotted for voice quality, diction, and pronunciation, personality, and general style. The judges’ task was to select five competitors, each of whom was to receive a guinea prize and the opportunity of taking part in a final test of _ actual broadcasting from 3DB. Suite a number of ladies entered for le preliminary contest, and two of them were so evenly matched that the judges divided one of the prizes between them. • * * • To test the amount of absorption of electromagnetic waves in tho earth’s upper atmosphere, Dr Hoyt Taylor, president of the American Institute of Radio Engineers, proposes to transmi-. short-wave signals to tho moon. His intention is to measure the strength of tho “echo,” judging that this should be heard 2.85e0 after transmission,- as the waves, J ravelling at 186,000 miles p r second must cover 500,000 miles. • * • • Dramatic performances are now being arranged as part of the broadcast transmissions to Scottish schools. The subject of tho first of .heso is pure history, consisting of three episodes from the history of Edinburgh. Castle.