RADIO RECORD

Greymouth Evening Star, 18 April 1929, Page 8

RADIO RECORD

NOTES FOR LISTENERS-JN

(By

"Reception”)

INVENTION OF VALVE. SUBSEQUENT EVOLUTION.

Without th© invention of the radio valve broadcasting would be impossible, and radio would have stayed where Marconi had placed it solely as a means of Morse communication. In the year 1884, what is known as the “Edison effect” was' noticed in the Edison laboratories. When a metal plate was placed between the two edges of an ordinary carbon filament electric lamp, a stream of electrons passed from the negative leg of the filament to the plate. Prbfessor Fleming an English scientist of note, conceived the idea of turning this Edison effect to account in the year 1904, and produced a two-electrode valve. His experiment had proved that a caioon filament, inheated to incandescence, and surrounded by a metal plate, acted as a rectifier, but was not as sensitive as a crystal detector. In the year 1908 Lee de Forest, experimenting in wireless telegraphy, observed that a snark coil, when connected to r source of current supply, affected the light from a Welsbach incandescent gas burner. He deducted that heated gas molecules were sensitive to high frequency oscillations. In 190 b, de Forest added a grid, or third electrode, to Fleming’s two electrode valve, and termed the resultant valve an “audlon.” His circuit arrangement for testing out this three electrode valve was just a simple one-valve circuit. Since that time the improvements on the first valve have been rapid. In 1913, Captain Round introduced an improvement to prevent Cathode rays, as the electron streams are called, from reaching the walls of the glass enclosing bulb or tube. In order to accomplish this, he completely surrounded the filament with a grid of wire gauze, protected by a metal cylinder.

SIMPLE SOLDERING. Soldering is really quite simple, the main idea being merely to heat the surfaces which have to be joined together sufficiently for solder to adhere to them. When they are thus warmed, solder can be “run” across from one surface to another, and on this cooling it will set as one mass, thereby joining the two surfaces together. The great art is to keep clean both the iron itself and the working surfaces. First of all the iron must be “tinned,” which is done by heating it in a clear flame (a gas jet is ideal), till it commences to burn with a green flame. When this occurs it can be removed and filed till it is bright, and whilst still very hot it should be dipped into a little flux and a blob of solder, in a tin lid. The melted solder will then run over the clean surface of the iron and coat it with a bright covering of solder, and then the iron is warmed up again ready for business. Whilst it is reheating the two surfaces can be thoroughly cleaned with a file or emery cloth, till the bright metal shows, touched with a little flux and then brought into contact of the hot iron until a thin coating of solder appears on them, also. (In other words, until they are “tinned” also.) When both the surfaces have been tinned, they are held together, the iron is heated again, and then it is placed over the two surfaces so that it can simultaneously and equally heat thefii. 'When hot enough the bloob of solder adhering to the iron will readily run over the two surfaces and these should be held perfectly steady until it solidifies, which it does a moment afterthe iron has been removed. At ibis stage and 'before the joint has had time to get cool, wipe it over with a clean cloth so as to remove any trace of superfluous flux. The heat will have liquified this, and it can be removed easily and quickly, but if it is left for a little while it will get cool and become greasy, and then be exceedingly difficult to remove, If, however, the above hints are borne in mind soldering will become a very easy and pleasurable occupation.

THE CRICKET TESTS. Says 2FC’s publicity department:-s-Perhaps it would not be out of place here to make available to listeners some of the enormous detail which has had to be covered to keep them in touch with the games that have been played during the cricket season. The preparation of the descriptions of the test matches alone occupied one hundred and eighty-one hours, and filled over seven hundred and forty sheets of foolscap. Four hundred and twenty-four trunk calls were linked up, and over 2500 miles of trunk lines were brought into operation during the games, while the actual transmission time in telling the progressive story of those matches occupied sixtyseven hours twenty-two minutes. The cost, to the company in giving this service totalled nearly £3OO. Commencing at 12 o’clock each day of the tests, the programmes of 2BL and 2FC were so arranged that both stations were available right up till the close of play. Records were established in several directions covering the total mileage in land lines used, the synchronisation of transmissions from both stations, and the progressive description of the whole series of test matches.

U.S.A. LEADS. Of 862 .short-wave stations throughout the world (aside from amateurs) as listed recently, nearly a third, or 246 in number, are in the United States and the Philippines, and 125 in various parts of the British Empire. Germany has 81, Holland 75, France 56, Japan 36, Italy 28, Russia and Brazil each 24 t Mexico 19, Sweden 17, Argentina 10, and China 10. In the case of the nations which have stations in their colonial possessions, even at a considerable distance, these are included in the above numbers. The majority of these, of course, are code stations. There are, it is calculated, between 50 and 130 meters, 884 channels suitable for point-to-point communication, under the international allotment of frequencies. Of these the United State Government has already allocated 228, or over 25 per cent., and it is evident that the longdespised short waves are of high commercial value.

NEW DESIGN RECEIVERS.

STANDARDISED A.C. SETS.

Mr Hooke, deputy general manager bf Amalgamated Wireless (Australasia), Ltd., explained to a conference of radio dealers from the different 'Australian States and New Zealand the outstanding features in the new receiving sets, which are being placed on the market for 1929. The principal development is in the standardising of all-electric sets. These are being made with six valves for interstate reception, and with three valves for local reception only. Prices are being substantially reduced, whilst 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. Whilst his company pioneered the industry he was delighted by other concerns, with a reputation for high-class goods. He knew that radio apparatus manufactured in Australia was equal to the best produced else'where, and he spoke with authority, as he had worked in shops in Britain 'and Canada as well as in Australia.

POLE- SUPPORTS. The pole supports or guy wires attached to the aerial have to be watched, and where a number of steel wires are employed, they must be broken at top and bottom with ins.ulators. Some say, “Why the necessity to insulate at both top and bottom?” Well, with an iron or steel pole any induced currents will flow upward through the wire and down the central pole if 'only insulators are used at the bottom of each guy wire. More attention is ‘paid to this stay wire insulation on a transmitting aerial than on one employed for reception only. It should always be remembered when erecting the aerial installation to sink a foot, which may consist of several bricks or a piece of totara wood on which the aerial pole stands. Otherwise after one or two windy nights the guy wires will be found to be getting loose due to the pole working further into the ground. Once a guy wire becomes loose, the pole is in great danger of falling during a storm.

STATIC. The New York Science and Invention states: “Static is an atmospheric electrical discharge. Radio waves are also of an electrical nature, but the static electrical disturbances superimpose themselves on the radio receiving system at unexpected moments. There is nothing so far which will filter this static charge out and yet permit the current to pass along the antenna. Static can be grounded the same as any other’ radio wave. It passes along the wire directly to ground or water. Static will - pass through a vacuum as easily as a radio wave and perhaps even more so because the discharge is frequently stronger; but in spite of this, a vacuum tube placed in series with the ground and the antenna will only ground heavy static charges, but will not prevent those static charges from making an audible sound in the loud-speaker of the radio set.”

OVERCOMING DEAD SPOTS. The endeavour to increase the field area of a. powerful station by opet-' ating two synchronised transmitters on the same wave-length and programme, to cover the “dead spots” which attend reception in any modern city area, has led to the licensing of a supplemental three- to five-kilowatt transmitter for KYW. Chicago. This is owned by the Westinghouse Company, which has operated WBZ at Springfield, Mass., and WBZA' at Boston for three years on this plan; and is evidently satisfied with the general results obtained. AVON has also been authorised to use a one-kilowatt transmitter to supplement its present 15-kw. station near Elgin, ILL., covering the Chicago territory.

GUIDE FOR AIRCRAFT

LONDON, February 3. A new serial system for transmission and reception of wireless telephone messages while flying lias been installed in a big 22-seater air liner on th© Imperial Airways service between London and Paris. Tho existing aerial consists, of trailing aerial which must be wound in when the machine approaches the ground so that the pilot is unable to use the wireless when nearing an aerodrome.

Tho new aerial, however, is fixed to the wings and can be used when the machine is on the ground so that in fog an air liner can be guided right into an aerodrome by means of wireless.