WIRELESS NEWS

Press, Volume LXVI, Issue 19972, 5 July 1930, Page 10

WIRELESS NEWS

(By "MAX.") One of the principal aims of th© radio manufacturer is to use as few valves as possible in a receiver. In this respect he has been very much assisted by the development of the screen grid tube, rhere are two main types, one with two grids and one wiHi three grids.

■the function of the first grid, which of course is present in the simpler three electrode valve as well, is to accept the signal voltages and control the plate current. In other words, it acts like a valve controlling a nozzle in a high-pressure pipe. We all know that A jet of water strong enough to knook a man down can be managed by a child operating a suitable valve The "control" or signal grid, therefore, with weak power supplied to it, operates the plate current in the same way, and the varying voltages in the plate circuit, set up in this manner ae a result of the changing currents, can be passed on to tho grid of another valve, giving still mpre power in the second stage, and so on. # » The screen grid serves quite another purpose, as it was added to act as a btatio screen to prevent, as much as possible, interaction between the plate and control grid, between which it is placed. Any change in plate voltage (set up by changing plate current) changes the tension, or voltage, on the plate, and this seta up an opposite charge upon the grid, making it negative if the momentary plate voltage is higher than normal, and rice versa. To make a long but interesting story short, it is this unwanted "feedback'' of voltages which causes troublesome oscillations to be set up, with its attendant violent distortion. « # The insertion trf the screen grid, together with a suitable positive voltage upon it, almost entirely eliminates undesirable feedback, and so about all that is necessary to avoid oscillation troubles is to enclose the tuning stages in metal boxes, or shields. The difficulties of neutral mntion are then overcome, and, besides this, there is a much greater amplification by each valve. This then cuts down the number of valves required. * # The very high amplification occurs because the screen grid serves a second purpose, that of assisting electrons emitted from the filament (forming the plate current, to be exact) to reach the plate more easily. A bigger stream of electrons is then under control and small voltages upon the grid are operating larger changes of plate current, giving gienter power changes, and large variations of power in tho plate circuit are what we want, provided there is no distortion; but this is another branch of the subject.

Unfortunately, with certain operating conditions with the screeA grid ralve, some of the electrons hit the ?fate with such force that other eleoroni are knocked out of the plate, and coining too close to the screen grid, with its positive potential which also attracts electrons, are taken ap by the screen grid, and the plate current actually drops instead of risen

Here is where the third grid cornea in, as it is placed between the screen grid and the plate, is connected to the Slament by a suitable lead, and itself acts as a screen for preventing this robbing of electrons which sho»M ijo to the plate. Its voltage or potential is the same as the filament, which is virtually aero.

The net result is that we have a valve which has more usefulness than the ordinary screen grid valve when it comes to handling greater power, for larger variations of plate current obviously pass on greater energy to another valve, if one is used, or work a loud-speaker with more force.

At least one make of pentode, as the valve with three grids is termed, can give about two watts with a plate current of about forty milliamperes at 950 volts high tension. Provided a suitable type of speaker is in the circuit, this rill give all the volume that the average man wants.

* ■» _ The loud-speaker must have a resistance of between four and eight thousand ohms for this purpose, when at least one and a half watts of power will be produced the maximum of two watts occurring with 6000 ohms. Within f the above values the second harmonic will not be over emphasised, being not more than five per cent.

The Radio Olympia, in accordance with a plan agreed to by the principal wireless firms in the Dominion, is being held much earlier this year. Opinions of dealers who are exhibiting {Mint to a very successful affair.. The .stands are novel and-attractive and a competition has been staged for all buyers of tickets.

the different sections have had no trouble spared in an endeavour to make a harmonious whole. The layout of the rooms, etc,, gives the Radio Society of Christchurch and the Canterbury Branch of the Transmitters' Association a better opportunity to make an effective display.

la England < there Are special radio inspectors whose duties inolude the overlooking of portable receivers, on the road and in oamp, to make sure th&t no olid is dodging the license fee. To take fl set whetl enjoying a picnio ie a Comtton occurrence these days, arid so 00 opportunity is missed to catch defaulters of revenue.

The Gdtefftfilefet of Colombia is using its radio station at Bogota to help in the unemployment difficulty. £Delp*Wanted advertisements are broadcasted free, as well as situation possibilities.

Dr. Mahlon Loomis, ( well known among the dental profession of his day for improvements in the dental art, was the first to send wireless messages over appreciable aibtanfees. In 1866, in the presence of eminent scientists, Dr. Loomis sent messages between stations situated on mountain tops in Virginia, 18 miles apart, and on Chesapeake Bay between ships two miles apart. * #

By his method he hoped to communicate with Europe ana other Continents. Without funds, he appealed to Congress for some £IO.OOO to mnke practical commercial application of his patented invention Congress passed the Bill, but never appropriated the money.

For many years, until his death in 1886, Dr. Loomis struggled tinsucce&sfully to finahce his project. His patents show his principles to be stiiefitifically those Marconi later put into commercial use, some thirtv yean after bootaia' first discoveries.

w # Thus Dr. Loomis never lived to mq tiie day when vnrelees would result in the saving of lives at sea, internatiOMl communication and the many other purposes for which it hat g} neo been developed.

Notes From Far and Near

BROADCASTING. TO DAY'S - PROGRAMME. 3YA, christchurch. (980 Kilocycles.) ; 230 p.m.: Rslay ' rorQ Lancaster fark— Rugby football —Running description ot the Second Tent match —Great Britain versus New Zealand. 6-0: From tho Radio Olympia at the Art Gallery, Durham street. Children's hour, conducted by Aunt Pot, Dnels Charlie and Birdman. 0.0: Return to 3YA *< mi in for dinner session musie (Columbia). 7o • Return again Radio Olympia ni tho Art Gallery, Durham street. 7.80: Snorts results. 8.0: Chimes. Special presentation of Charles Lawrenco'g "Minstrels' in old-time and present-day nigger melodies, nlantfttion part songs, jokes, comicalities and tap-dancing. 0.0: Weather report and station notices. 9.2: Return to BYA studio. Novelty—Syd. Howard and Company, "Our VilCe Concert." 9.10: Orchestral—lnternational Concert and Orchestra, (a) "Lazy Pete" (Werner); (b) "Parade of the Wooden Soldiers" (Jessel). 9.16! Soprano —Jeanette MacDonuld, "Dream Lover Girl'' IUHnV Holmes): "Eldgaffcln" (Landen). 9.30. Returning again to the Radio Olympia at tho Art Gallery. Durham street. Second portion of Charles Lawrence's "Wastrels in old-time and present-flay nigger melodies, nlantation part songs, jokes, comicalities and tap-dancing. 10.30: Dance programme, "H.M.V." hour. BZO, CHRISTCHUROH. (250 Metres.) 10 am.: Women's session. "Coriolan Overture " American Symphony Orchestra. 10.8: Tested recipes. 10.25 a.m. i "Second* Bhap* sodie" (Liszt), Rachmaninoff (piano); "Punchinello," Edmund A. Jahn (baritone); "Viennese Popular Bong," Vera Barstow (violin); "Tho Winding Trail," Frederick Kinsley (Wurlitzor organ); "Since First I Met Thee," Floronce Ferrell (soprano); "Dream Flowers," waltz Intermezzo, Imperial Marimba Band! "Par from Thee," waltz, Ernost L. Stevens (piano); "Old Black Joe," Christine Mitler (contralto): bnllet musio from "Rosamunde," Vera Barstow (violin); "Muddy Water." Frederick Kinsley (Wurlitzer organ); "When Love is Kind*' and "Jenny," Amy Ellerman (contralto); "Dance of the Nightingales," Imperial Marimba Band. 11.80 p.m.: Close down. 2YA. WELLINGTON. (720 Kilocycles.) 2.45 p.m.: • Chimes. • Running description of tbo second Rugby Test match between Britain and New Zealand, on relay from Christchurch. 5.0: Children's session, conducted by Uncle Toby. 6.0: Dinner musie session, "H.M.V." hour. 7.0: News session, market reports and sports results. A special Manx programme In honour of Tynwald Day, the national day of Manx Race. 8.0: Chimes. Overture—The Salon Orchestra (conductor, Mr M. T. Dixon), "Keltle Suite" (Poulds). 8.9: Choir and organ— London Manx Choir, "Elian Vannin" (Manx national song) (arrgd. Poulter). 8.12: Solo and chorus—Mr A. G. Flanagan and Melodio Four. "Ramsay Town" (Crabb). 8.10: Choir —London Manx Choir, "Manx Fisherman's Hymn" (Harvest of tho Sea) (trdtl.). 8.19: Talk—Mr T. E. Corkill, president of the Manx Society. "The Isle of Man." 8.84: Shanty—Mr R. 8. Allwright and Melodie Four, "Steamers Three." 8.38: Piano—Mr M. T. Dixon, "Manx Aits" (Wood). 8.45: Song—Mias Nora Gray, O, What if the Fowler my Blackbird has Taken" (arrgd Gill). 8.49: Bass—Mr W. W. Marshall, "When Chllder Plays" (Davis). 8.54: Recital—Mr T. E. Corkill, "A Recital in Dialect." 8.58: Baritone—Mr W. McHarrie, "Ny Kiree Fo Nalshtey" (The Bheep under the Snow) (trdtl.). 9.1: A brief address In Manx by Mr T. E. Corkill, followed by the Manx National Anthem, sun* by the London Manx Choir. Adapted by W. H. GUI 9.4: Weather report and announcements. 9.6: Instrumental—Salon Orchestra, "Request Item." 9-I*' Quartet—Melodie Four, "Down at the Huskin- Bee" (Wilkins). 9.18: Novelty plan® i-Mr Claude Bennett, (a) "Sleepy Piano' (Magree); (b) "HumorestleSs" (Oonfrey), 9.23: Tenor—Mr Sam Duncan. "Songs Mr Mother Taught Me" (Dvorak). 9.87; Instrumental— Salon Orchestra, "Selection— Glorlana" (Frlml). 0.35: Humour—Mr Will 'Bishop will entortaln at the piano. 9.45: Soprano— Miss Nora Gray, "Break o' Oaf (Sanderson), 9.49: Novelty piano—Mr ClatWo Bennett, "Ivory Lace" (Alter). 9.53: Tenor—Mr Frank Bryant, "When YOU Come to tho End of the Day." 9.57: Quartet—Melodie Four, "Request Item." 10.1: Injtmmental——Salon Orchestra, " Dance Novelettes." 10.0: E-ance programme, "Brunswick" hour. IYA, AUOKLAND. , (900 Kilocycl»s.) 3.45 p.m.: Rugby football tnatah frcrS# Eden Park. Announcer, Mr Gordon Hutter. 5.0: Children's session,' conducted by Cinderella. 6.0: Dinner session, "Parlophono" Hour. 7.0: News and market repotts. 8.0: - Chimes. Overture—Mare* Wsber and his Orchestra, "Leheriann " (Gelger). 8.9: Tenor—Mr Roger Errington, "Serenade" (Schubert). 8.13: Overtule—lYA Orchestral Octet, under Conduotcrship of Mr Eric Waters, "Martha (Flotow) 8.22: Band—H.M. Coldstream Guards, "Teddy Bears' Picnic" (Bratton). 8.25: Novelty trio —The Snappy Three, (a) "Louisa" (Whiting); (b) "In a Little Love Nest" (Tucker). 8.88: Orchestral—lYA Orchestral Octet, (a) "A Forest Wooing" (Anoliffe): (b) "Funeral March of a Bumblo Bee (Marsden). 8.42: Vocal with Spanish guitar. Mr W. L. BenboW. (a) "Maori Hula Medley" (own composition); (b) "Ninlpo—Hawaiian Hula Soar" (unknown). 8.48: Organ—Jesse Crawford, "Rotes of Yesterday" (Berlin). 8.51« So'ection —IYA Orchestral Octet, "Mignon (Thomas). 8.57: Malo quartet—National Cavaliers, "Beautiful" (Gillespie). 9.0: Weather forecast and announcements. 9.3: Orchestral—lYA Orchestral Octet, Tone Poem, the Selfish Giant" (Ooates). 9-12: Tenor—Mr Roser Errlngton, (a) I Hear You Calling Me" (Marshall); (b) "Sally in Onr Alley" (Carey). 9.19: Band— H.M. Coldstream Guard#, "Down South (Myddleton). 9.22: Novelty trio—Snappy Three (a) "Piano" selected; (b) A Kiss, a Caress, and then Adieu; (c) Latest Hit" (all by Sharp). 9.88: Orchestral—--IYA Orchestral Octet, "Turkish Patrol (Mlchaelis). 9.37: Voc&l wlthSpanish guitar, Mr W L. Benbow, (a) 'Chatigeabla Woman" (own composition); (b) Al Jolson's Melodies Medley" (Al Jolson). 9 45- Organ—Jesse Crawford, "Just a Night for Meditation" (Lewis-YoungPollacK). 9.48: Male quartet, The Revellers, O Luoindy" (Holllngsworth). 9.51: OrcheS' tral—lYA Orchestral Octet, (a) Foltwt, E+ar, on a Night Like This" (Conrad): (b) "Foxtrot Bella of St. Mary, s (Allati). 10.0! Programme of dance musie, h.m.v. hoUr ' 4YA, DUNEDIN, (650 Kilocycles.) 180 p.m.! Running description of football matches. 8.0: Children's hour, conduct, ed by Aunt Anita. 6.0: Dinner wusic"HMV." hour. 7.0: New® sedli&fc. 8.0: Chimes. Relay 61 concert flrograramd frdtti Christchurch Radio Olympia. 10.60: D&nee prograitiitid till 11 p.ttij 1 ■■ • SUNDAY. 3YA, CHRISTCHURCH. 8 p.m. Relay of annual Choir Festival frotfl East Belt Methodist «lurch. PMSefitatlon nf the beautiful oratorio, The Story or Mtislc," bjr Ernest Nichol, Mus. BaC. VOdAl soloists:— Soprano, Mrs J; A> Stewart I Contralto Mrs J. W. Palk; Tenor, Mr Ernest Roger's • Bass, Mr James Filer. Supported and accompanied by full Chdlr, striae orchestra, and organ. Ohoir conductor, fir J. Chaplin; Organist, Mr A. M. o*en. 4.16: Musical recording from BYA Btudio 6.30: Children's song service, by Children Of Methodist Sunday Schools. co .^ ac Kev. Rugby Pratt, assisted by the Children from the Methodist Sunday Schools. 6.15: Musical recordings from BYA studio. 6.85: Relay of evening service of Annual Choir Festival from East Belt Methodist Church. Prfiicher Rev. W. Greenslade. Choir con ductor Mr J Chaplin Organist, Mr A M. Owen 7.45; Hymns and anthems from BYA studio. 8.15: Selection—Menorah Symphony

The Americans are usUallv fery shrewd in recognising the value of scientific discoveries, but on this OWSIU sion they missed the opportunity to develop one of the modern miraew*,. •Jfr # A new short wave-length has been allotted the Swiss Government in addi. tion to those already in use for con. tinuous wave transmissionTOe. Call sign is HBC and the wave-length 34.64 metres. 4fr * The Isles of Greece are to be linked tto with Athens and the mainland by ,Xless telephone and Mtdmnb *jr> vices, for which the Greek Government has ordered equipment. Th«® of the latest type Marooni «tfttion« for duplex telephony eraphv are to be erected, one in or near Athens, one on the Island of Crete, and the other on Chios.

Orchestra, "Bar Xocbba" (Goldfaden). 8.23: Mesio-soprano—Mrs Grace Empson, "Ombre Mai Fu" (Handel). 8.27; Violin —Miss Irene Morris, "Air" (Goldmark). 8.81: Bass baritone —Barend Harris, (a) "Bells of the Sea" (sung in English); (b) "Song of the Volga Boatmen" (with explafl&tory remarks) (sung In Russian). 8.41: Instrumental trio—Christchurch Broadcasting Trio, "Allegro Vivace" (from "Trio in D Major") (Baethoven). 8.53: Mezzosoprano—Mrs Graee Empson, (a) "Have You Seen but a White liily Grow!" (old English; arr. Lisa Lehmann); (b) "O Pair and Sweet and Holy"\ {Rubinstein). 8.59: Weather report and station notices. 9.1: Instrumental trio—Christchurch Broadcasting Trio, (a) "Serenade" (Mozart) (from "A Little Night Musie"); (b) "Tempo di Minuetto" (Godard). 9.18: Bass baritone — Barend Harris, (a) "Shir Shomerin" (sung in Hebrew) (The Song of the Watchman) (A Palestinian Folk Song); (b) "My.Song of the .Nile" (suiig in English) (with e* planatory remarks). 9.23: Violin—Miss Irene Morris, "Allegretto" (BoccheriniKrelsler). 9.96: Orchestral—Budapest Philharmonic Orchestra, "Rakoczy March. 2YA, WELLINGTON.

9 p.m.: Chimes. Afternoon session. 4.0: Relay from St, Paul's Pro-Cathedral ot the Rally of the Combined Anglican Bible Classes (speakers, Archdeacon Creed-Mere* dith, Rev. Whitby-James). 6.0: Children's song service, conducted by Uncle George and assisted by the Children's Choir from the Mlramar Presbyterian Church, under the Rev. Mr Hitchcock. 7.0: Relay of evening: sarvlce of St. Gerard's Redemptorlst Church (Organist, Mr H. Mount; Choirmaster, Mr F. J. Cakes. 8.16 (approx.): Relay of the Band Recital of the Port Nicholson Silver Band, from the Grand Opera House (Conductor, Mr J. J. Drew). IYA, AUCKLAND. 8 p.m.: Afternoon session—Selected studio items, Including literary selection by the announcer. 6 0: Children's son? service. 6.55: Relay of Divine Service from St. Matthew's Church (Preacher, Rev. 0. H. Grant Cowan; Organist and choirmaster, Mr J. Phi!pott). 8.80 (appro*.): Relay of concert by Municipal Band, under the oonductorship of Mr Christopher Smith, from Auckland Town Hall.. 4YA, DUNEDIN. 3 p.m.: Ohlmes. Selected gramophone items. 6.80: Children's song service, conducted by Big Brother Bill. 6.80: Relay of evealftg service from First Church (Preacher, Dr. Hunter; Organist, Dr. V. E. Galway). 7.45: Selection—Classic Symphony Orchestra, "Pagllscci" (Leoncavallo). Chorus—Roysl Choral Soolety, "Hallelujah" and "Amen" (frota "Masslah"—Handel), Piano—W. Backhaus, "Studies, Op. 66'* (Chopin). 8.5: Relay of concert by Tramways Band, tinder direction of Mr C. Morgan, ttaw His Majesty's Theatre.