THE RADIO WORLD

Hawke's Bay Tribune, Volume XVII, 30 November 1927, Page 9

THE RADIO WORLD

HINTS FOR LISTENERS. NEW SCREENED VALVES. Valves of novel design will soon be on the market. Additional to the type which will work direct from the mains, there will be a screened valve especially planned to give tremendous H.F. application, Whereas the normal amplification of an H.F. valve is from 4 to 7. according to the circuit and coupling system, the latest introduction is promised to give an amplification of 17. It will be used, of course, in a specially-de-signed circuit, which i s somewhat similar to the old tuned-anode plan once so popular. The valve has to be screened. A new four and also a six-electrode valve is hinted at, whilst an ultra-powerful L.F. amplifier will, it is predicted, enable us to use one L.F. stage where hitherto a couple have been necessary. HOWLING AND ITS PREVENTION. What is “howling.” and how is it caused?” i s a question one often hears from amateurs whose neighbour are inconsiderate enought to oscillate over the top of them. For the benefit of these get owners I shall try to explain as lucidlv as possible just what howling is, and its causes (States Magna Vox in the “Otago Daily Times”). Whenever the output circuit of an audio-frequency amplifier is coupled to the input circuit, instabalitv in the amplifier will very likely be produced, and this will result" in howling. The output of any audio frequency amplifier tube. has many times the voltage of the input. Suppose, for instance, that the grid of one of the amplifier tubes is set into vibration one way or another, possibly by someone with big feet walking across the floor of the room in which the set is located. As the grid vibrates, its relative effectiveness to the value of the plate current changes in synchronism with the vibrations of the grid. The plate current follows the frequency of these vibrations, and if, due to poor wiring, this plate lead passes ' sufficiently close to the grid lead of the tubq, therewill be a feedback of energy from the output circuit ro the input circuit, with the result that the oscillations will be maintained. and will manifest themselves in the loud speaker output. The remedy for this is to be sure that none of the wires from the plate circuit is coupled to any of the grid leads. JOINING TANTALUM ELECTRODES Listeners who employ the popular tantalum rectifier for accumulator charging or high-tension supply purposes may experience trouble if tile connecting joint to the tantalum electrode is not very carefully made. Tantalum does not anneal when heated, but, instead, becomes extremely brittle. It cannot be soldered, and a mechanical point is therefore a necessity. A good clamp of brass z-ill perhaps provide the best solution of tile difficulty, and the joint should afterwards be well coated with antisulphuric enamel. I PROGRAMMES FOR TO-NIGHT. IYA, Auckland—6 p.m.: Children’s hour. 7.15: Talk on "The Comets” by Mr. J. Collier. 7.30: News and reports. 8 : Chimes; relay of orchestral selections from Strand Theatre Orchestra under the direction of Eve Bentley, and assisting artists. 2YA, Wellington.—Silent Day. 3YA, Christchurch.—6 p.m.: Children’s tour, Uncle Peter and Mother Hubbard, assisted by the junior members of the Scottish Society of New Zealand, who will sing a number of Scottish songs. 7.15: Addington stock market -reports. 7.30: News and reports. 8 : Chimes ; relay of orchestral selections from Grand Theatre Orchestra under the direction of Mrs Black; pipe band, Scottish Society's Pipe Band, (a) “King’s Own Scottish Borderers,” M. 5... (b) “Believe Me If All Those Endearing Young Charms,” M.S., (c) “Captain Jack Murray," (d) “Mrs McLeod," M.S.; baritone solo, Mr. J. North. “Hail, Caledonia,” Stroud; choral items. International Choir, (a) “Come O’er the Stream. Charlie," (b) “My Love, She’s But a Lassie Yet”; recital, Master David Dickson, “The Bachelor"; instrumental trio, Christchurch Broadcasting Trio, (a) “Trio No. 6, Allegro," (b) “Andante,” (c) “Finale.” Bohm;'contralto solo, Mrs D W. Stallard, “Angus McDonald.” M.S.; Scotch chorals. International Choir, (a) “The Wee German Lairdie,” M.S., (b) “Duncan Gray,” M.S.; ’cello solos, Mr. Harold Beck. (a) “Ca the Yowes to the Knowes,” Scottish, (b) “Turn Ye to Me." Scottish; Scotch humour, Mr. J. Laureuson, “The Chairman’s Remarks" ; relay of orchestral selections from Grand Theatre; Scotch »ong, Mr. Peter Donaldson. “Loch Lomond and You.” M.S.: mezzo soprano solo. Miss Anita Graham. “Caller O’u,” Gray; Scotch chorals International Choir, (a) “Over the Sea to Skve, ’ (b) “Tho Three Crows"; warpipes solos, Piper J. A Patterson, (a) “Athol Highlanders,” (h) "The Blue Bonnets,” M.S.: baritone solos Mr. J. North, (a) “The Lass that Wears the Slanter," Hewisou. (b) “The Standard on the Braes o’ Mar,' Driver; soprano .solo. Miss Jean Dickson. “Cornin’ Thro’ the Rve”; instrumental trios. Christchurch Broadcasting Trio, (a) “Afton Water,” Scottish, (b) “Flowers M tho Forest.’’ Scottish, (c) “Ye Banks and Braes.” Scottish • contralto solos. Mrs D W. Stallard. (nV “Afton Water,” Hume, (b) “Doon the Burn,” Hook; recital, Miss Jean Dickson “Kirkcaldio”; Scotch song. Mr. Peter Donaldson “Hame o’ Mine.” Murdoch: warpipes duets, Piper J. A. Patterson and PipeMajor W. Fowler (a) “Willie McKay’s Farewell ” M.S., (b) "The Green Hills of Tyrol,” M.S.: vocal duet, Mrs D. W. and Miss Bessie Stallard. “Wert Thou in the Cauld Blas?” Mendelssohn; ’cello solo, Mr. Harold Beck, “Mazurka. Op. 11, No. 3.” Popper; mezzo soprano solos, Miss A. Graham, (a) “’Twas Within a Mile o’ Edinboro’ Toun,” Scotch, (b) “Scottish Bluebells”; instrumental trio. Christchurch Broadcasting Trio. “Andante and Scherzo,” Mathias; Scotch humour Mr James . Laurenson, (a) “Poet of Dunrobin, ’ M.S . (b) "Wee Scotch Night,” M.S.; Highland warpipes. Scottish Society’s Pipe Band, (a) “Cock o’ tho North,” M.S., (b) "Tam Glen," M.S.; “Auld Lang Syne.”

4YA, Dunedin.—Silent day. 2BL. Sydney—b p.m.: Broadcasters’ Topical Chorus, Mr. Clement Q Williams (baritone songs), Mr. Robert Gibson (cornet solos), Miss Grace Quine (popular ballads), the Canterbury District Band. Mr Jack Cannot (Australia’s popular comedian). 3LO, Melbourne.—7.ls p.m.: Mr. C. C Brittlebank on "Disease Control in the Flower Garden”; Mr, P. W. Pearce on “Swedish Drill.” Artists: Bobby Pearce, Reginald Bradley Victoria Wilson. Len Gibson’s Neapolitan Sextette. Maggie Foster. Syd. L. Exton, Mary Mack, Jack 6’Hagan, one-act play, Kyneton Brass Band. Era Spry’s Orchestra. 4QG, Brisbane.—B p.m.: “The World’s Call” meeting will be relayed from the Exhibition Hall.