THE WIRELESS WORLD.

Otago Daily Times, Issue 21063, 27 June 1930, Page 5

THE WIRELESS WORLD.

NEWS AND NOTES. By Alaoka 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, _ rrT „ , Aletres. 7ZL, Hobart .. .. 535 -3AR, Melbourne 4844YA. Dunedin 463 2FC. Sydney 442 2YA. Wellington 420 4QG. Brisbane 385 3LO, Melbourne 371 2AB. Sydney 316 2KY. Sydney 280 ANSWERS TO CORRESPONDENTS. “ Four Valve,’’ Clyde.—The distortion is probably due to high-frequency leakage into the low-frequency circuits. Try inserting a high-frequency choke between the grid of the amplifying valve and the lead, which is connected to it. J. D. O’H., Dunedin.—lf your last valve appears to be getting much warmer than it should do, have a look at your grid bias and make sure that the battery is connected properly and is in first-claes order. Also see that you are using the proper grid voltage. “ More Power,’’ Green Island.—You can secure a high-voltage supply quite simply by placing two B. eliminators in series, the total voltage being the sum of the separate units. In this ease, the positive terminal of one B. eliminator goes to the negative of the next. The high voltage is then taken from the two extremities. In the same way, a dry battery can be hooked up - with an eliminator to increase the voltage. “ Henry,” Dunedin,—lf all the apparatus is in good order, and grid bias and other voltages are of the proper value, the powerpack should carry the load easily. Watch for any cause of excessive current, such as a partial breakdown in a condenser, a short in a choke, in the wiring or the plate circuits, or absence of grid bias in the output valve. A milliametcr of suitable range would be of considerable assistance. Keep a careful watch for any rise in temperature, as the fault may develop only through this cause. The . rectifier should have five volts applied to filament and preferably not more than 300 v on each side of the centre trip. STATION 4ZB. Listeners all over Otago will. be interested in the innovations which are being introduced into the transmissions from 4ZB, the station of the Otago Radio Association. The station director (Air R. T. Stedman) has intimated that, in order to give a greater and more extended service to. listeners, a live children’s service will be conducted each Thursday, and this will be followed by a book talk each week by Mr J. W. Webb, who has undertaken the duties of chief announcer. Two assistant announcers have been appointed in the persons of Messrs N. D. Briathwaite and H.F.Tattersfield. In view of the fact that 4ZB is heard to advantage all over Otago district, it has been decided to announce the Burnside stock sales report every Wednesday evening. The children’s. session will: be heard every Thursday from 6.30 to 7.30 p.m. It will be a bright affair, calculated to give young radio listeners a very, happy hour on 4YA’s silent night. .Young performers, many of them of exceptional ability, will assist the announcer. Technical matters in connection with the transmissions are receiving careful attention, and the operator (Mr R. D. .Mitchell) is gradually introducing many improvements which will doubtless go a long way to make 4ZB’s transmissions more popular than ever. Reports, upon the transmissions and programmes continue to pour in from all over the country, showing that the station has many interested admirers. WIRELESS FOR THE VATICAN. Signor Alarconi continues his research work on board the Electra and in Italy, and has prepared wireless plant which will allow the Pope to give viva voce benediction to. all the world, from Sydney to Alaska. Signor Alarconi. is controlling the final adjustments of the Vatican City, transmission station, which has been constructed to his model and under his personal supervision. Work at the Vatican is being intensified so that the installation will be complete before the- end of the Pope s jubilee in July. Signor Alai coni is being kept advised of the tests to date, and by consultation he has made dispositions whereby on Sunday, June 29, on the Feast of St. Peter and St. Paul. Pope Pius XI will be able to send greetings to the Sovereigns and beads of States which have diplomatic with the Holy See, It is therer i “ oped *-hat His Holiness will ■ be able to transnut his voice in benediction to Catholic missionaries who will go on pilgrimages to appropriate receiving stations at Alaska, Tokio, and Sydney. LOUD SPEAKER TONE QUALITY. Tone quality from loud speaker depends not only upon the sound reflecting and absorbing conditions of the. room in which p ,. hut also upon the location ot the listener. Even when all reflections of sound are eliminated, as, in outdoor measurements, it is found that low notes are subject to a greater radiation to the side than are high notes. The higher the narrower the sound beam in C ?S.n B f a i pe J son who sits directly L- a lou d speaker will hear a greater portion of high notes than will f a £nr S °£J ho « Blts t 0 one aide - Another factor that influences tone quality is' the rlr»m ier 8 £rou> a speaker. If too c j rtai ? frequencies may not be heard, due to the interference between arrlve ’> different phases different parts of the diaphragm. It P° 6S, °.le so to place a fine loud ;® r o. position in a room that it will give poorer tpne quality than placed^ 101, speakcr which is better RADIO IN THE ARGENTINE. It is expected that South America will experience a genuine radio boom this year as a result of the action of the Argentine Government m taking over control of broadcasting. There are 22 stations within the city limits of Buenos Aires, and these stations have been deviating from their assigned wavelengths. The result was that broadcast reception was extremely poor, owing to interference Th» Government since taking control,' has ordered all broadcasting stations to move their transmitters out of the city limits during the next nine months. The Secretly of Communications in the Argentine Cabinet will enforce this regulation. The beflef ! 5 expressed that with reception conditions improved as a result of Government intervention, the use of receiving sets will increase considerably. In spite p °°L, rece J? tlol l conditions and the fact that little attention has so far been given to the production of programmes, the deSv nd * or . receivers has been quite brisk. The 22 broadcasting stations in Buenos Aires have been presenting extremely Sketchy entertainments made up almost entirely of gramophone records. FIXED CONDENSERS. Either mica or pa‘per is the insulating material placed between successive leaves of metallic foil that form the plates of small fixed condensers. The better this insulating material does its job the better the condenser, provided the material is up to standard in other respects. Although even a paper condenser hae a resistance to direct current of some hundreds of megohms, a very slight leakage may m some cases upset completely the working of a set. Many fixed condensers are used to couple one valve to another They are placed with one lot of leaves in the plate circuit of the previous valve, and the other connected into the grid circuit of the next valve. A grid leak of perhaps one or two negohms takes care of the grid. Now a leakage of only one millionth of an ampere through a leak of a million ohms will give rise to a voltage drop across the grid leak of one volt. Tins means the grid will become one volt more positive. A leak of ten times this amount would cause a dron of 10 volts and the working conditions of the set would be completely upset. Instead of having, say a negative grid voltage of five, it might be turned into a positive voltage of five. Naturally the set would give bad results. Paper condensers are useless for work of this type for on normal plate voltages many of them do allow currents of several millionths of an ampere to flow. Mica, however, is a much better insulator and a good mica condenser, while very compact, does not allow even a fraction of a millionth of an ampere of direct current to flow- through its insulation. Moreover, a iwina. con-

denser should last almost indefinitely. Although many people do not realise it, two times out of four the reason for poor results may be traced to. poor condensers in hey positions. MISS AMY- JOHNSON'S ARRIVAL. The thrill and excitement of “ Johnnie’s ".arrival in New South Wale# was shared to a large extent by the Australian Broadcasting Company, who sent up a plane with Mr Norman Lyons as announcer, and Mr S. A. Colville, hon. radio engineer of . the Aero Club, to broadcast the description of “Johnnie’s" arrival 6000 feet above the ground. Mr Colville installed in the Aero Club Moth DH9 a crystal-controlled power amplifier of 10 watts, which he had designed and constructed himself. The power was supplied by dry batteries comprising 400 volts high tension, and eight volts low tension for filaments lighting. Preliminary testa proved that the crystal transmitter was most satisfactory, and the broadcast was picked up in North Queensland. inland Victoria, and South Australia. as well as furthermost New South Wales, which is. a wonderful record, as this was the first crystal transmitter used in communication, from an aeroplane to the ground by telephony. It reflects the greatest credit on Mr . Colville. The pleasure of giving “ Johnnie ’’ her. first aerial greeting fell to Air Norman Lyons, who picked up the giant Fokker containing “Johnnie" as it was flying over Manly. • Excited at seeing the tripleengined machine, Mr Lyons had the pilot of the DH9 fly the machine alongside the one containing “Johnnie," and waved the microphone to her. This, was “ Johnniu’s " first aerial greeting. To -say that Air Lyons was delighted at the famous air girl’s reciprocal wave is only putting - .t mildly. The thrill of it went into the microphone, so that . all listeners could share iC The DH9 left Mascot at 1.30 p.m. The plane headed north, and after climbing 2000 feet it was found that the reception was good. The plane went up as far as Palm Beach, on the lookout for “Johnnie.” .The DH9 saw a Fokker going along, and derided that this was .the Brisbane mail with “Johnnie” aboard. To add to this assumption, when Barren joey was reached, much to their surprisethey saw the formation wheeling round and fall into position on either aide of the Fokker. So the DHO went after her. They chased her all the way to Mascot under the impression it was “Johnnie.” whilst the formation flew with them. When the DH9 saw the Fokker take the hangar they knew they had been on the wrong track, and sped away north again. When they reached Broken Bay. they looked back arid saw the formation again surrounding a -Fokker. ■ The DH9 wefa! for their life, chasing the Brisbane mail, and broadcasting the thrilling description of how the machine was gaining on' the Brisbane mail. It was whilst they were passing Fort Denison that they flew alongside the Fokker, and Mr Lyonswaved the microphone at “Johnnie.’ The entire hour and a-half spent aboard the DH9 was filled to the utmost with interest for the announcer, the engineer, and the pilot. Mr Lyons says’he has 'not'yet recovered from the diving feats of the plane chartered by the Australia Broadcasting Company. Sli? dropped from 5000 feet to '3OOO feet, and dropped into an air pocket, which isn’t a too pleasant experience for one. not accustomed to long flights. However.. he agreed it was an experience well worth while, and sincerely hopes that another young woman can b persuaded to fly from England to Aim tralia. so as to enable him to take the air again, as' broadcasting announcer.