RADIO AND ITS RECEIVERS

Sun (Auckland), Volume III, Issue 634, 10 April 1929, Page 14

RADIO AND ITS RECEIVERS

SETS FOR THIS YEAR CHEAPER AND SIMPLER Mr. Hooke, deputy-general manager o£ Amalgamated Wireless (Australasia), Limited, explained to a conference of radio dealers from the different Australian States and New Zealand recently the outstanding features in the new receiving sets, which are being placed on the market for 1929. The principal development is the standardising of all-electric sets. These are being made with six valves for inter-State reception, and with three valves for local reception only. Prices are being substantially reduced, while the sets are being made simpler to manipulate. In fact, all that is necessary in the new design receivers is to plug a connecting cord into a wall socket connected with the home electricity supply, turn a single dial and one station after another can be tuned in with certainty and assurance. Mr. E. T. Fisk, managing director, in an address to the dealers, expressed satisfaction that the manufacture of radio receivers was being extended in Australia. While his company pioneered the industry he was delighted that it was being taken up so generally by other concerns, with a reputation for high-class goods. He knew that radio apparatus manufactured in Australia was the equal to the best produced elsewhere, and he spoke with authority, as he had worked in shops in Britain and Canada, as well as in Australia. Members of the conference inspected the transmitting apparatus at Pennant Hills, where, in addition to local broadcasting, messages are transmitted to all parts of the Pacific, and to ships at sea between Australian and British and American and Canadian ports. DARGAVILLE HEARS LONDON (From Our Own Correspondent) DARGAVILLE, To-day. A local wireless enthusiast, Mr. 11. Gaukrodger, tuned in to Chelmsford (London) at 6.30 one morning last week on a four-valve set. At loud speaker strength “Big Ben” was to strike 7 o’clock, and the broadcast of a medical lecture was easily audible. Several musical items

Conducted for THE SUN by R. F. HAYCOCK

RADIO IN AUSTRALIA INCREASE IN LICENCES The large and steady increase in the number of licensed listeners in New South Wales during the past six months is attributed to the improvement which has been effected in the programmes of 2FC and 2BL since the management of these stations was coordinated and brought under single control. This has prevented the overlapping of programmes that was so prevalent in the early part of last year, and has enabled greater variety to be introduced into the entertainment provided by both stations. The experience in Britain, as well as in America and other countries, has been that the number of listeners to any station has a direct and intimate relation with the class of programmes provided. The British Broadcasting Company has found that listeners will tolerate a considerable amount of educational broadcasting if there is ample variety in the entertainment side, and if those who do not want to be educated have an opportunity of listening to an alternative programme from another station. Throughout Britain and Ireland all listeners, even the users of crystal sets, have the privilege of alternative programmes each evening of the week, including Sundays, whilst those with more powerful receivers can listen to scores of stations in different parts of Europe. Under the new arrangement between 2FC and 2BL and 3LO and 3AR, when an “A” station in Sydney or Melbourne is putting a classical or instructional programme on the air, the other station provides popular entertainment. The “B” stations in Sydney have recently specialised with high-class musical selections, and have found it to their advantage to curtail their “publicity” sessions, and not to make their advertising matter too prominent. The united competition of the “A” and “B” stations has so improved the entertainment programmes that listening has become increasingly popular in recent months. The manufacturers of receiving sets anticipate an increased volume of business during the coming year.

S.G. VALVE VOLTAGES j SUPER-SENSITIVITY Many sets and circuits employing the screen-grid type of valve have been described, but as a rule it is not clearly pointed out that the operating voltages with this type require close control. For example, it is sometimes vaguely stated that the screen-grid should have a “high positive bias,” but in practice it will be found that this voltage is often quite critical and that it varies considerably with changes in other factors in the circuit. In some conditions 20 volts may be satisfactory; while in other conditions, up to within 10 volts of the plate voltage may provide the most sensitive operation. It is therefore clear that if this super-sensitive valve is to be employed at maximum efficiency—which is generally the intention when using it in place of the ordinary three-elec-trode valve —a source of high voltage is necessary, together with some more or less micrometric means of controlling the voltage. One obvious means is to control the voltage by means of a stepless resistance of very large range, using a by-pass condenser of up to 1 mfd. connected across between the screen-grid terminal and the negative end of the filament, so as to prevent feed-back and oscillation. The variable resistance is adjusted until the greatest amplification is obtained. The anode voltage and grid bias j with the screen-grid tube are as a rule not particularly critical. TRANSFORMER QUALITY The ability of a low-frequency transformer to deal properly with the lower musical frequencies—the frequencies which give mellowness to the reproduction—depends upon its inductance. According to the chief engineer of a well-known firm of transformer manufacturers, the transformers used in a receiver from which a high standard of reproduction is to be expected must have a high inductance. “In the manufacture of audio transformers,” he says, “there has been a steady increase in the size of iron core used, the purpose being to give greater inductance to the transformer. “In the primary of an audio-trans-former there are both direct and alternating currents, the direct current flowing from the high-tension supply to the anode of the valve and the alternating audio current flowing through the anode and filament circuits through the primary and so in the secondary. “The direct current tends to saturate the core of the transformer and reduce its effectiveness in handling the alternating current. “It is for reasons of this nature that extra large amounts of iron are now used, in order that the value of the core may be so large that even with the high anode voltages and currents used in modern radio receivers, the direct current saturation point of the 1 core may not be approached.”

j K.M.O.X. ANNIVERSARY MONTANA ON THE AIR A Taltapuna listener reports: On turning round the dials on March 31 I had the good fortune to pick up K.M.0.X., which was celebrating its anniversary. The announcer stated that “The Voice of St. Louis, Montana,’* would continue on the air until 6 a.m. American time. The programme consisted of Wurlitzer organ request items and songs from the studio with plenty of pep. They were receiving telegrams from all parts of U.S.A. asking for items, and not one was refused. The organ was working overtime, and could only play one verse of any song asked for. Reception was every bit as loud as IYA, with the exception of slight fading every ten minutes. Our local New Zealand stations could take many a leaf out of the Yank’s book to improve the programmes. One thing is certain, the American listener receives good service, with no repetition of items.

RADIO TERMS ILLUSTRATED

SHORT-WAVE TESTS NEXT SUNDAY The New Zealand Association of Radio Transmitters, Auckland branch, is holding an 80-metre fone and telegraphy competition for local amateur transmitting stations on Sunday, April 14. The first station competitor will ? commence operating at 10 a.m. and will be followed by others at intervals PANAMA TALKS TO BYRD Short-wave radio communication from Panama, nine degrees from the Equator, with the Byrd expedition in the South Polar region was established by the Tenth Signal Corps of the army recently, according to a report at the military headquarters at Balboa. A new portable short-wave set, designed and built by the members of the Signal Corps, was used, the transmitter being operated on small storage batteries.

AUSTRALIAN “A” STATIONS

NO ALTERATION IN CONTROL

Last the broadcasting companies in Sydney, Melbourne, and in other States, were invited to form one central company, with which the Federal Government would negotiate for an extension of the existing licences when they expired, the Government having determined that broadcasting could best be conducted by one private enterprise. It now appears certain that owing to difficulties which the postal authorities have encountered in the obtaining of plant, the A class stations will not be transferred on July 1 of this year. It has been learned by the wireless trade —which had been pressing to know what was happening—that the Government is more than inclined to ask all A class stations to carry on until January, 1930.

Toward the end of 1928, after tlx ; Director of Posts and Telegraphs, Mr. | H. P. Brown, had returned from the ; conference which dealt with the merger of the cable companies and the beam wireless organisations, the Prime Minister, Mr. Bruce, without warning, announced that he had determined that the Government should take over the mechanical side of broadcasting, while one central company would be asked to provide programmes for the whole of Australia. This, of course, meant the fixing of a date upon which the Government would assume control of the A class stations, or else bring into being other stations in their place. Sihce the Government had on niauy occasions pledged itself to establish relay stations in the country, it followed that one general turnover had to be arranged. The A class stations were asked it they would carry on their businesses until their licences expired, or (in the case of Sydney) until a date some weeks later. They were also asked to agree to a date that would be suitable for all Australia. They did so. The Federal Government then endeavoured to persuade the Queensland Government, which at the time, it was understood, was intent on conducting its own station—an attitude it has maintained since the inception of broadcasting—to retire from the field.

It would appear, by the way, that the postal authorities have been unable to bring to maturity their plans for new A class stations, cr for relay stations, and that they had been unable to negotiate terms with Amalgamated Wireless to provide the plant that may be necessary. Further, it is declared that the postal authorities are determined upon building their own stations, which would mean a very definite setback

for Amalgamated Wireless, which has in the past provided all facilities for 2FC -Sydney, and 3LO Melbourne. There is some suggestion that, apart from technical difficulties, the Federal Government is rather embarrassed by claims which have been made by the different broadcasting companies for compensation, which, they state, is due to them, because of the manner in which the Government has conducted its negotiations.

TRANSMITTERS’ COMPETITIONS

A competition on the 75-85 metre band has been organised by the Australian Radio Transmitters’ League (N.S.W. Div.), for the members of the league. This competition commenced on Sunday, March 31, and finishes on Sunday, April 14. A special prize has been allotted to the New Zealand or inter-State transmitter, who has the most QSO’S with members of this league during the competition period. All members who are desirous of participating should advise the organiser, W. H. Barker, 12 Wallace Street, Concord, N.S.W.