THE WIRELESS WORLD

Otago Daily Times, Issue 22609, 28 June 1935, Page 3

THE WIRELESS WORLD

NEWS AND NOTES

By Magna Vox

Items of local interest are invited by " Magna Vox" for publication in this column. It is necessary that such matter should reach this office by Tuesday of each week for insertion on the following Friday. » . 2UL, Sydney.—Bss K.C., 353 metre*. 2FC, Sydney.—66s K.C., 422 metre*. 3AR, Melbourne.—62o K.C.. 492 metres 3LO Melbourne.—B3o K.C.. 371 metres. SCL, Adelaide.—73o K.C.. 395 metres. 4QG, Brisbane.—76o K.C, 385 metres. IYA, Auckland.—6so K.C, 461.3 metres. 2VA. Wellington.—s7o K.C, 526 metres. 3YA, Cliristcliurch.—72o K.C, 416.4 metres. 4YA Dunedin.—79o K.C. 379.5 metres. 4YO. Dunedin.—ll4o K.C, 261 metres.

ANSWERS TO CORRESPONDENTS. " Super-het.," Ranf urly.—Unless you can let me have some further information, I am afraid it is impossible to say what is causing the trouble. Sometimes oxide filament valves will rejuvenate for a while after keeping, but this applies mainly to power valves, and then is not to be relied on. As a rule, such valves will show traces of excess gas in the envelope. Can you give me more details about the set, as beyond the fact that it is a six-valve super-het., I am in the dark.

G. F. T., Roslyn.—The best field coil to use is one of 750 ohms. If there is any hum in the set through insufficient filtering with this resistance, a iiiter choke of 120 mills, rating can be connected in series with the field. The 2As's are generally preferred to 59'e these days, although I do not think that the advantage is very considerable. Apart from these points, the original set is still one of the best standard broadcast typea on the market. - "Derf," Oamaru.— (1) I am afraid you have been the victim of a somewhat mean practical joke. Why, before doing as your " friend" advised you, did you not consult a reliable serviceman. lie could have told you at once that the proposition was quite an impossible one, and that none but the mentally-afflicted would otherwise. (2) I shall forward you a circuit on receipt of of postage, but I should like it understood that I do so in a very exceptional case only. (3) There is certainly no such station, and your informant's description of the broadcast he heard must have been born of a pretty vivid imagination. (4) I should say that the reply to this query would be fairly obvious. If the station had broken down, how did the announcer manage to warn listeners.

"Ampere," Makikihi. —The speaker field is a little lower than that generally used, hut' I doubt whether the slightly higher total output voltage would be important. Try connecting the output from the two outside terminals of the transformer, or between one outside terminal and the centre tap. Use which ever connection gives the better results. It very rarely pays to .use cheap valves in a set, and you are certainly not going the best way to get really good results and service free from . trouble.

WIRELESS AND THE PRESS. At a recption by the Lord Mayor to the Australian Newspapers Conference delegates at Brisbane recently, Mr A. 0. C. Holtz declared that he was not a bit afraid of radio as far as the newspapers were concerned. Radio's chief function was entertainment, and it would develop on those lines. Newspapers had a definite place in the community, and they appealed to a definite audience. "You cannot defy the press, because you, cannot choose your audience," continued Mr Holtz. " You might think you are addressing thousands, but they might be on another station or listening in boredom and waiting for the entertainment to follow. The press is infinitely more powerful than the radio." THE NEW STATIONS. Preparatory work in connection with the new 4YA transmitter is proceeding apace. An engineer has arrived at Dunedin from Australia to erect the 500 ft steel mast, the base portion of which has already arrived. Considerable work has been carried out on the foundations of the transmitting hall and on the near-by residential quarters. Altogether the work is now catching up on schedule, and it is conssidered that the station will be completed before the due date. No intimation has yet been received as to when 3YA will be transmitting on itsincreased power. It is estimated that the new Wellington transmitting station will be on the air about this time next year. Tenders will be called next month for the transmitter building. Unofficial suggestions are that it will be built at Titahi Bay or near Pencarrow light-, house. The only official news is that it will be about 20 miles from Wellington. The new YA is to have an aerial power of 60 kilowatts THE WORLD'S LISTENERS. A survey made by the United States Bureau of Foreign and Domestic Commerce based on " the best references available" gives the number of receiving sets in use in the world as 53,582,474. These are supplied with programmes from 58 long, 1537 medium, and 136 short-wave broadcasting stations. Statistics from 131 countries have been combined to produce this total, which sets forth the position about the end of last year. North America, with over 26,000,000 sets in use, and Europe, with about 22,000,000 receivers, are easily at the head of the list of continents. The United States, with 25,551,569 receivers and 631 broadcasting stations, is the most plentifully supplied individual country, while Abyssinia, with five sets and no stations, is at the bottom of the list. Only 45 countries of the list, which includes many small islands and dependencies, are not provided with transmitters of some kind. COMPREHENSIVE PROGRAMMES. One would have thought that 7.30 in the morning was an early enough start for anybody, but the German authorities have determined that their listeners shall become even earlier birds than we are • in New Zealand. In future the main German stations are to start their day at ,5 a.m. and to close down at 2 o'clock the following morning. They will thus be "on the air" for 21 hours out of the 24. The object of the early morning broadcasts is stated to be to provide mental recreation for the manual workers, particularly peasants engaged in agriculture. A further series of concerts for factory workers is to take place between 6 and 8 a.m. It may be that the German agriculturists and the factory hands will respond to the invitation to switch on their sets at these unearthly hours. MEXICAN PROPAGANDA. Station XECR has been opened by the Mexican Ministry of Foreign Affairs " to carry out active propaganda of news on behalf of Mexico's good name abroad." In an official notice we read that " XECR will serve lofty aims, as in addition to broadcasting all over the universe the truth in regard to the situation in Mexico, it will do its share towards drawing closer the bonds of international friendship and rectifying by actual facts distorted world opinions in regard to the Republic of Mexico, originated by malevolent and misleading reports." XECR works on 40.6 metres (3780 k.c). every Sunday from 11 p.m. to 12 midnight, G.M.T. GIVING LISTENERS A CHANCE. Believing that the only bar to the complete enjoyment of broadcast programmes is the listener's inability to re- I ply, the Stuttgart station authorities are | introducing a listeners' programme once | a fortnight. During these two-hour ses- i sioiis representative listeners are led to the microphone and permitted to catechise the station director on matters pertaining to the arrangement of programmes. MOTOR RADIO. The Minister of Transport has had • under consideration the use of wireless

sets in cars, and has decided, according to the London Daily Telegraph, not to ban them, though he may make regulations about them. Mr Hore-Belisha has recently written to the Society of Motor Manufacturers and Traders stating that no evidence has been adduced to indicate that wireless should, on grounds of public safety, be prohibited- in motor vehicles, and as at present advised he proposes to make only such regulations as may appear to be necessary to prevent the danger of fire and to avoid interference with the driver's control of the vehicle. The Minister has promised to consult the motor manufacturers before taking action. He thinks it desirable that the sets used for car radio should not be powerful enough to be a source of annoyance. Motor manufacturers are for the most, part little interested iil the matter. Though extremely popular in the United States, where 75 per cent, of new cars are said to be titted, car radio has made little headway in Britain. Of some 500 American cars imported into England last year with wireless as a standard fitting, the purchasers of nearly 90 per cent, asked that the sets should be removed. ULTRA SHORT-WAVES. British wireless discussions are now concentrated very largely upon television and various questions arising out of it. As television has enforced the use of waves as short as five or six metres, the technical problems connected with transmitting and receiving these " ultra-short" waves are at the moment paramount. Transmitters do not offer any fresh difficulties: the laboratories have long since produced suitable designs. The five-metre receiver, however, is another matter. One of the hurdles to be overcome is that amplification at extreme frequencies is not very efficient, and so the radio-frequency circuits are tricky to design and make. Another is that the range of frequencies used in the new television system giving line definition is enormous —from about 20 cycles per second to about a million—approximately a hundred times as great as is required to give the highest quality of broadcast reproduction. The lowest frequency, twenty cycles a second, is below the reproducing range of many receivers; and the highest, a million cycles, is not found at all, but is in fact the frequency of a 300-metre radio wave. Considering that radio engineers who are making sets commercially are in the habit of bragging if their products have a " flat characteristic" from 20 or 25 cycles to 8000, imagine what it means to extend the scale to 120 times that length! However, it can be done. Designs have been worked out giving an overall characteristic, for that vast range, better than is often found in the small range of musical frequencies. Apart altogether from transmitting and receiving apparatus is the question of getting the signal from transmitter to receiver. The governing factor is the apparently ragid behaviour of ultra-short waves; they travel, like light, only in direct lines, so that if the transmitter cannot see the receiver—that is, if the direct course is obstructed by hills or by the curvature of the earth, the transmission to that receiver will fail. In practice the working distance is of the order of from 25 to 100 miles, the limit being fixed by the height at which the transmitter can be placed. It has been explained in this column previously that no ordinary wire line will carry the very high frequencies used in television; and reference has been made to the invention of a special type of line (one conductor inside a second, tubular, one) which promises a solution; but it is a very costly one. There is just a possibility that fuller .investigation of very short waves will show that they may be found at greater distances than those covered by a direct line, and investigations into this matter are alreadv in hand. The London Chapter of the International Short Wave Club, which has a membership in 92 countries, has instituted testa (they were to begin on May 19) from a transmitter on the roof of the Daily Telegraph office. It is only a five-watt transmitter, but very short waves do not require great power to give them a good range. There is as yet no evidence that very short waves are reflected or refracted in the upper atmosphere as longer ones are. (hence their extensive range), and the testa are for the purpose of finding out. Morse and telephony tests were to be used, and amateurs were asked to cooperate by listening for them.