OVER THE AERIAL.

Auckland Star, Volume LVIII, Issue 195, 19 August 1927, Page 15

OVER THE AERIAL.

(By "PHONOS.")

Tabloid radio evolution:—(l) Incredulity; (2) Ridicule; (3J We all knew it would happen.

During the past few nights Australian reception has been very good. 2FC came in particularly well with a good programme on Wednesday.

According to a Dunedin paper, Mr. A. R. Harris is at present in that city in connection with the installation there of a new station "on the lines of the stations at Auckland, Wellington and Christchurch.

->lany New Ztalanders are familiar with the transmission of JOAK, the strangely-lettered Japanese station. There is also en the air anotuor Japanese station, sending from Nagoya, on 360 meters. Its call sign io So far no protest has been made from Scotland.

Are we getting a decided surfeit of picture orchestra items from IYA? Thirty eight or forty minutes of orchestral music (served in two slices) in a programme is an almost nightly dish. When this music is merely incidental to a film it has little appeal. Of course, it is cheap entertainment for the Broadcasting Company, and at times it is cheap in other respects.

The Auckland Listeners' League have been considering the question of holding a radio Olympia in Auckland, and have been assured of enthusiastic support for the project. The local dealers, however, consider that from their point of view such an exhibition would be coming rather late in the season, for from the trade point of view radio is a seasonal industry. It is likely therefore that the Olympia will be deferred till early next year.

One sometimes has to go far afield to gather news. The following is from the "Sydney Morning Herald": —"2YA, Wellington, has at present a power of five kilowatts, and there is a proposal to increase that power to 12 kilowatts, or double that of any of the present Australian broadcasting stations. The object in view is to make 2YA serve for all New Zealand, and to use the Auckland, Christchurch and Dunedin as subsidiary stations, and mainly for local broadcasting on certain nights only."

In its transmission 2YA continues to be a .disappointment. Its volume is about, equal to that, of 2FC, but is is far from as steady as Farmer's, and its programme cannot be enjoyed unless one is handy to adjust the set controls from time to time. It certainly is not living up to the claim that was made for itc— that 2YA would reach over the whole Dominion. One might be tempted to suggest that an experienced technical man might diagnose and remedy the present troubles, and perhaps use more of the available power. MORE ABOUT ROYALTIES. - Many have wondered why radio export to New Zealand from Britain has been so slow of development. One of the principle deterrent factors has undoubtedly been the haziness on the question" of patent rights and their infringement. Now comes a very definite statement on this matter. Mr. Topham head of the patent department of Mar eoni's Wireless Telegraph Co., Ltd., made the following statement during a recent interview. "Any licensed manufacturer can now obtain permission to export receivers to Australia and New Zealand. A payment of 15/ per valve holder must be made to this company before dispatch. We retain 2/6 of this sum, the remainder being handed over to Amalgamated Wireless (Australasia), Ltd., in full satisfaction of their claims. No other royalty payment is then required." Commenting on this the "Wireless Export Trader" says: "We do not know definitely, but we are given to understand that the patents on which Amalgamated. Wireless base their claims are registered only in the Australian patent office, and that they impose royalties on sets sold in New Zealand on the score that their title includes Australasia, and that New Zealand is in I Australasia."

WIRELESS NEWS FROM FAR AND NEAR,

THE DETECTOR VALVE AND HOW IT WORKS.

The valve used for radio reception consists of three elements, the filament, grid and plate. The filament is used for the purpose of throwing off electrons through the grid to the plate. These electrons are caused by the filament being heated. The grid acts as a shutter, and controls the flow of these electrons between the filament and the plate. Electrons are very small particles of matter, so small that the powerful microscope cannot make them visible. They can carry an electric current, and by so doing make a path from the filament to the plate. The plate has always a positive potential applied to it by means of the "B" battery, and this causes a difference in electrical pressure between it and the filament, and by this means attracts to :tself all the negative electrons emitted by the filament. It is a well known electrical fact that like potentials repel, and, unlike potentials, attract each other. Now, if the grid of the valve is made negative it repels the electrons and decreases the current carried on them from the filament to the plate. Therefore if a negative potential is applied to the grid it decreases the current passed by the valve, but if a positive potential is applied to the grid it helps to pull the electrons from the filament, and increases the current passed by the valve. A very small change in the voltage of the grid will make a very great change in the current of the plate circuit, and it is this fact that makes the valve so valuable for radio work. The very minute changes in voltage picked up by the aerial from a distant transmitting station are impressed on the grid and several times as much current is taken out from the plate. The current taken from the plate comes from the "B" battery, but the incoming signal controls the passage of this current through the valve and so through the telephones. Immediately the filament of the valve is lighted, there is a current passing through the valve. This current has a certain value, and remains constant so long as the polarity of the grid remains unchanged. If the charge on the grid is changed either by an incoming signal or by putting a battery in circuit with it, the current flowing through the valve is changed. Now these changes in current caused by the incoming signal are very fast, too fast to be audible. The only effect which would be audible are the slow changes in the average current drawn from the "B" battery. Now to do this, one-half of the incoming oscillations picked up by the aerial have to be suppressed, and this is done by the valve only passing one-balf of the oscillation, and so giving undirectional impulses. This faculty enables a valve not only to detect but also to amplify. When a condenser is placed in series with the tuning coil and the grid, it permits the current to pass through to the grid. Now the electrons on their way from the filament to the plate are permitted to pass when the grid is negative and stopped when the grid is positive. The electrons 6tay on the grid when a positive potential is applied as if it were a small plate, then when the oscillation has shifted to the negative side again and back to the positive, the positive charge added to the grid is not so great, because the grid has a negative charge of its own, owing to the electrons, which are negative, being collected. The condenser prevents the electrons from flowing back to the filament through the tuning coil as they would do if permitted, and so the grid becomes more and more negative. If this was allowed to continue the valve would become paralysed, and therefore the high resistance, known as the grid leak, is shunted across the condenser, and permits the electrons to escape after they have been used for biasing the grid and making the valve detect. The proper capacity condenser, which is generally about .00025 microfarads, and the proper valve grid leak, which i 3 usually around two million :>hms, must be used to get the best results from the valve as a detector.

WAVE LENGTHS AGAIN. | In a minor way we are likely to experience the difficulties in reception that have been the worry of listeners both in Europe and in America. More stations and higher powers are being developed in our part of the Pacific, and it seems that a conference "on wavelengths that will embrace more than Australia and New Zealand will seen be necessary. A writer "on the other side" puts the position thus:— Wellington' 3 new wave length of 420 metres, combined with the high power transmission, makes interstate reception of 2FC and SCL, Adelaide, exceedingly difficult. With the big majority of receivers—even of first-class commercial design—2FC completely "blankets" 2YA, j and the interference of 2YA makes the reception of SCL almost impossible in the vicinity of Sydney. In other States there is the difficulty of satisfactorily separating 2FC from 2YA. It is exceedingly unfortunate that there was not some basis of co-operation between the Australian and New Zealand Post Ofcce Departments when the new ,/ave lengths for the Dominion were being allocated. Had there been co-operation 2YA would have been more widely separated from two important Australian stations, and wireless exchj nges between the two countries thus rendered more easy of accomplishment. Further trouble will, in all probability, be caused to Australian listeners by the rapid development of radio in Japan. Two of the new Japanese stations will have a power of 50 kilowatts, and there is talk of JOAK, Tokio, having a power of 100 kilowatts. The wave length of that station is 375 metres, and on a power of 1 kilowatt, which has been previously used, its transmissions were heard nightly in Australia. With a power of 100 kilowatts it will, on nights favourable to reception, be heard as strongly in Australia as any of the interstate stations, and render the reception of 4EG increasingly difficult. \Vith the Manila station contemplating an increase of power, and the possibilitv of the Dutch Government erecting a wireless station in the Dutch East Indies probably of 50 kMowatts, the fixing of that length for the proposed State Government stations will be one of difficulty. It is quite evident that many important matters regarding the development of radio in Australia will have to be taken into consideration before any additional high-power broadcasting stations are licensed in the Commonwealth.