WIRELESS NEWS

Press, Volume LXVIII, Issue 20552, 21 May 1932, Page 8

WIRELESS NEWS

By "MAX." Crystals carefully cut and ground from quartz are used to control the frequencies of transmitting stations. In the natural form quartz occurs in sixsided slabs or crystals, sometimes fairly large, and at first glance one would think that the hand of man had been at work grinding and polishing them to shape. A specimen weighing about 201b can be seen at the Franz Josef Glacier Hotel and one end presents a tapered appearance, Nature fashioning this end to a blunt hexagonal point. The clarity of the crystal at once appeals to the eye, but few people apart from wireless amateurs are aware of one of the special uses to which this species of quartz is put, namely, frequency control;

There are two directions in which a slab of crystal can be cut when preparing it for this purpose, and each has certain advantages. The thickness of the final ground article determines the frequency which it will vibrate at, but there is a slight difference between the two cuts. Special care has to bo taken to grind to an even thickness, or thinness, for some are very thin when prepared for high frequencies. Unevenness, or slight chips, might easily render the finished crystal useless. Tine carborundum powder with water on a fiat slab is generally used by amateurs who grind their own crystals. The crystal is mounted between two perfectly tint pieces of brass, as a rule, and is connected in the grid circuit. If the plate circuit contains a coil and variable condenser, and' the dial of the latter is slowly rotated, then the whole circuit will osciliate when the correct tuning, to suit the frequency of the crystal, is reached. This outfit can then be used to control a transmitter by connecting it up in the proper manner. For keeping the frequency of a transmission stable to a very small margin (a comparatively few cycles above or below the desired one for which the crystal has been ground and tested) it is necessary to maintain an even temperaturo, and various devices are usod to attain this end. "Usually the crystal is in a special box with a thermometer to show the temperature, and apparatus to keep this steady at the correct value.

Not only can radio transmitters be controlled, but jt is also possiblo to operate a special clock, and ingenious methods will enable such a email margin of error to bo reached that perhaps only one second in a million will bo slipped.

The question cropped up recently as to tho correct use of tho torms "detection," "rectification," "detector," and "rectifier." All but the last are invariably applied to the action in a wiroless apparatus designed to convert radio frequency impulses into audio ones. The fourth term can be used more freely, and also covers any appliance for converting alternating curront into pulses of direct current, Tho commonest ones are the valve, and the dry type, such as the well-known Westinghouse. Valve rectifiers include varieties such as the half or full wave two electrode valves, consisting of filament and plate, the tungar, once so popular for charging "A" batteries up to a rate of 5 amps or so, and the mercury typo of valve. The latter, of which tho Rectobulb is a good example, can bo used for high voltages up 'to some thousands, and will deliver quite a heavy current with only a drop in volts of about fifteen. The Rectobulb is indirectly heated and requires about 20 seconds at least after the filament is lighted in order for tho valve to function properly. At our YA stations the plate voltage is delayed by an automatic appliance whieh comes into action when the filaments have the power switched on. Nothing is left to the operator who might be careless and cause damage to the rectifiers. The filaments in tho latter merely supply beat to a unit which vaporises the mercury, and if the anode voltage is applied too soon the delicate filaments have to supply the electrons forming the high tension current, and the filaments are liable to break down under the strain. There are other types of mercury vapour valves used as rectifiers, but they are not so suitable as the Rectobulb variety.

Radio reception on parts of the West Coast varies considerably. In some places excellent results of distant stations are secured, but YA stations are not very good. The Wellington station appears to suffer badly from distortion and fading. This accounts for the operation of a private B class station in Greymouth, Particulars of this transmitter' will be given shortly, hut it is owned and operated by an amatour for stimulating the radio trade. With the abundance of timber and mills one would expect to find nothing but wooden masts on the Coast, but it is surprising to see a large number of pipe masts."lt is rare to find a good aerial system. The poles are too short, stays too long, often longer than the antenna Itself, and with only one insulator.

Notes From Far and Near

BROADCASTING. TO-DAY'S PROGRAMMES. 3YA, CHRISTOHTTRCH (080 Kilocycles.) 3 p.m.: Gramophone recital. 4.30: Sports results. 5.0; Children's hour, conducted by Aunt Pat. CO: Dinner music. 7.0: News ond reports. 7.30: S'ports results. 8.0: Concert programme. Relay of programme from 4YA, Dunedin. 10.0: Sports summary. 10.10: Relay from 4YA. 3ZC, (1200 Kilo.) 5.30-U.15 p.m.: Children's session. li.lo--6.45 p.m.: Dinner music. 6.45-7.15 p.m.: Sporting and general news. 7.15 p'm.: Musical item's. 7.45 p.m.: Contract Bridge Talk (Mr W. Shackle). 8-10 p.m.: Evening concert session. 1011 p.m.: Dance programme. 2TA, WELLINGTON (720 Kilocycles.) 3 p.m.: Relay o£ description of Rugby Football Match, from Athletic Park. 5.0: Children's hour, conducted by Aunt Molly and Uncle Jasper. 6.0: Dinner music. 70: N'ovvs and reports. 7.30: W.E.A. Session: 'R. J. Waghorn, M.A., "The Earth and Man —The Future." 8.0: Concert programme. Recording, New Mayfair Orchestra, "Sous o' Guns." 8.8: Mezzo-soprano, Peggy Jones, (a) "Lovely S'pring" (Coenen); (b) "Slave Song" (del Riego). 8.14: Overture, Salon Orchestra. (Conductor, M. T. Dixon), "The Merry Wives of Windsor" (Nicolai). SAA: Recording—Ma!o Voices, Kanawha Singers, (a). "Good-bye, My Lover, Goodbyo"; (b) "That Good Old Country Town" (Robinson). 8.30: Novelty Piano, Mamie Reid, (a) "Concert Study in C" (Moszkow«ki); (b) "Throe Blind Mice" (Holbrooke). 8.36: Duet, Peggy and Vol Jones, (a) "Farewell to Summer" (Johnston): (b) "Rose of My Heart" (Lohr). 8.42: Selection, Salon Orchestra. "Mr Manhattan" (Talbot-Court-ney). 8.54: Recording. Earl Burnott's Bißmore Trio, (a) "I'm That Way About Baby" (Green): (b) "This is Heaven" (Akni). 9.0: Weather report and notices. 9,3: Humour, Wiil Bishop, "A Humorous Interlude." 0.17: Suite, Salon Orcb.es.trii, "Russet and Gold" (Sanderson). 0.27: Baritone, VM Jones, (a) "Cloze Props" (Charles): (b) "Gypsy Love Song" (Herbert). 9.33: Novelty Piano, Mamie Reid, (a) "Improvisation—Theme by Colly" (arr. Sims); (b) "Birth of the Blues" (Henderson). 9.39: Recording—Sketch, The Roosters' Concert Party, "Lights Out" (Merriman). 9.45: Fantasia, Salon Orchestra, "Tho Tyrolean" (Zsller). Latest Dance Novelties. .10.0: Sporting summary. 10.10: Dance programme.

SUNDAY. 3TA. OHRISTOHUECK. 2 p.m.: Gramophone recital. 5.30: Children's Song Service by Children from the Presbyterian Sunday School. 6.15: Chimes from studio. 6.30: Relay at evening service from St. Paul's Presbyterian Church, Oashel street. Preacher: Rev. Alan C. Watson. Organist: Norman William*. Chotr conductor, H. Blakoley. 7.45: Selected recordings, 8.15: Concert programme. Selection, Chrfstchurch Salon Orchestra, "The Talcs of Hoffmann" (Offenbach). 8.25: Recording, the Siebor Choir. "Tales from the Vienna Woods" (Strauss). 8.33: Recording (violin), Frederick Fradkin, "To ft Wild Rose" (MacDowell). B. 30: Baritone, J. H. Cooks, (a) "My Wfe Has Crept no Long" (Somervell); (1>) "t Sometimes Wonder" (Ross). 8.42: Piano recital, Fred Pace, (a) "The Princess" (Tscherepaine); (h) "Masurka in A. Minor" (Chopin): (<•) "Windmills (Moeran). 8.51: Contralto, Bertha Rawlinson, "Qhe Faro" (Cluck). 8.56: Recording (organ). Richard Jordan. "Song of the Islands" (King). 8.59: Bos», C'audo O'Hagan with Orcheetra. "The Bandolero (Stuart). D.y: Weather forecast and notices. 9.5: Salon Orchestra, (a) "Andantino (Lemare); (b) "Laughing Morjmiettß (Collins). O.U: Recording AVestminster Glee Singers, "Breeze- of the (Lamothe). 0,14: Recording, London JTluta Quartet. "Bees' Wedding" (Mendelsohn, arr. Stsiner). f.17: Bariton*, J. It. Cartr, (a) "The Lute Player" (.VUitsen); (b) The Last Hong" (Toatl). Salon Orchestra, four dances from "Rebel Maid" (Phillip*). 0.33: 'Reeordinsr (soprano), S.igrid 0n «5 1 ..' "Serenade to Zanetto" (Massenet). ».a«Recording (violin), Marta Lin*. Hejre Kati" (Hubay). 0.n9: Contralto, Bertha Rawlinson, (a) "When I »m L»'d »J> Earth (Purrell); (b) "Ring. Bells. Ring (Bay). 94 "Accordlne. Hermann Trio, in K Major" (Pelwwr). MR: B ™> GlM*e O'Hagan. (a) "Friend o Mine" gander; son); (b), with orchestra "The Lost Chord (Sullivan), 0.55: Recording Mandolin* Concert Society, march. "Ama»on'« Ride (It).ter). P 58: Selection. Salon Orchestra, "Haydn Wood's Songs" (arr. Hlfffe). 3ZC. (1300 Kilo.) 10-11.30 a.m.: Musical items, G. 13-745 p.m.: Dinner music. 6-0.50 p.m.: Concert session. 2YA, WELLINGTON. •_> to 4.30 p.m.: Selected recordings. «.<>: Children's Souk Service, conducted by IJnole Oeorgc, assisted by the Children's Choir -frop the Church of Christ, 7.0: Relay of Evening Service from St. Peter's Anglican ChuroU. Preacher: Rev. W. Bullock, 8.15 (appro*,): Concert programme. Relay of Band Concert by the 'Royal Naval Volunteer Besorve Band from the Pe Luxe Theatre (Conductor, Harry Balser).