RADIO AND ITS RECEIVERS

Sun (Auckland), Volume IV, Issue 1043, 6 August 1930, Page 7

RADIO AND ITS RECEIVERS

Conducted for THE SUN oy R. F. HAYCOCK.

PROGRAMME TIT-BITS

N.Z. AND AUSTRALIAN FEATURES A fine programme has been arranged for this evening at IYA. The vocalists will be Miss Martha Williamson (contralto) and Mr. A. Gibbon Taylor (bass baritone). Piano and vocai novelties will be given by "Eric and Jack” and Mr. Alan McElwain humorist, will again be beard. 2YA will not observe a silent day, and for the fourth day ot the Wellington “Music Week” there will be the usual midday organ recital and community singing. At 8 o’clock this evening there will be a relay from the Town Hall, where the Royal Welling ton Choral Union in co-operation with the Philharmonic Orchestra will present a concert. Two quartets will be heard from 3YA - Mendelssohn's well-known canon, “The Lark’s Song,” and “Nightfall in Hyderabad.” Interspersed in the evening’s programme from 4YA will be many dance tunes played by an excellent combination, the Collegians. A feature of the programme from 2FC tonight will be a music recital from the New South Wales Conserva torium of Music. This will start at 9.30 p.m. (New Zealand time). “The Spur of the Moment,’ a play by Betty Davies, will be broadcast from 2BL. An attractive studio concert will be broadcast from 4QG. THURSDAY EVENING The evening's session at IYA will contain a great variety of items. There will be instrumental selections by Ileg. Morgan’s Orchestra. Humour will be supplied by The Asquiths. The "Music Week” broadcast will continue from 2YA, at midday, afternoon and evening. In the evening there will be an oratorio programme, when Haydn’s “The Creation” will be relayed from the Town Hall.

3YA will be broadcasting on relay from the Civic Theatre the presentation in concert form ot Donizetti’s opera, “Lulia di Lammermoor,” by the Royal Christchurch Musical Society. 2FC will present a play adapted from “The Wrecker,” commencing at 9.30 p.m. (New Zealand time), and 2BL will give a recording of the colourful opera, “Carmen.” The programme from 4QG has been arranged by Mr. George Sampson, conductor of the State and Municipal Orchestra. FRIDAY EVENING At IY’A the Orchestral Octet will provide the instrumental portion of tiie concert. Four vocalists will appear: Mr. Frank Campbell (light baritone), Miss Beryl Smith (contralto), Mr. Duncan Black (bass) and Miss ' Joan Laird, a young soprano who has ; recently returned from England after some years of study. From 2Y’A, in continuation ot Wellington’s “Music Week,” at 8 o'clock there will be a relay of the Combined School Choirs and School Orchestras’ concert, arranged by Mr. Douglas Taylor, Director ot School Music tor the Education Department. The vocal artists tor SYA's concert programme will be Miss Merle Miller, Mrs. Rhys Morgan and Mr. Leslie Fleming, while humour will be broadcast by Mr. H. Instone. A special programme by the choir of Trinity Church, Dunedin, will be broadcast by 4YA. An excellent studio concert will be heard from 2FC, and the Lighthearted Duo will amuse listeners to 2BL. The Entertainers will feature English musical comedy items from 4QG. SATURDAY EVENING IYA will broadcast the concert to be given in the Town Hall by the Municipal Band, under the direction of Mr. C. Smith. The evening session from 2Y’A will be devoted to a relay of the “Grand Fijiale of Music Week,” which is being Ueld in the Town Hall. The official opening of the Christchurch Winter Show will be broadcast by 3YA. A vaudeville and dance programme will follow. Unusual syncopations of popular classics will be featured for the first time by 2FC. Vaudeville items will comprise the greater portion ot the programme from 2BL. Studio items and a boxing contest will be heard from 4QG.

REACTION CONTROL SHOULD IT BE PERMITTED? There are those who, say that no receiver can possibly give its fullest efficiency unless reaction is used, says a writer in “Wireless World.” There are others who maintain that it should be made a criminal offence to fit a reaction control to any set. Both views are extreme, but both contain a germ of truth. Reaction is usually associated with the use of a grid rectifier, where the grid current damps the tuned circuit to a very considerable extent. The effect of this damping, and of any other damping due to such causes as dielectric losses, can be nullified by the intelligent use of reaction. In a receiver ot this kind there is therefore a certain setting of the reaction control that invests the tuned circuit with the same resistance that it would have had if dielectric losses had been carefully minimised and an anode detector, which is free from grid-cur-rent damping, had been used. If reaction is pressed no farther than this its use can hardly be regarded as criminal, for the tuned circuit has exactly the same resultant resistance as in many receivers in which reaction is not used, at all. The use of reaction up to tfiis point may therefore be regarded as perfectly legitimate. There is, however, the temptation to increase reaction beyond this point in an endeavour to improve the sensitivity and selectivity of the receiver. Apart from the fact that this increase is liable to result in oscillation, to the infuriation ot every listener for miles round, the user of the set himself begins to suffer. Signals received when the set is on the verge of oscillation are always distressingly poor in quality, for the resultant resistance of the tuned circuit has been so reduced that the outer side-bands are not received at all. All high notes are therefore completely missing, music becomes just a noise, and speech is nearly unintelligible through lack of consonants. Such results indicate that reaction is being used to an illigitimate extent.

LANDING OF RIOO

UNSATISFACTORY BROADCAST A rebroadcast of a description from 2JA Montreal of the landing of the airship RIOO at Montreal was attempted by 2FC Sydney on Friday evening. Conditions were most unfavourable and little of what the announcer at 2JA said could be heard. In fact, if the Sy ’ney station had not said what was being broadcast listeners would have been none the wiser. News of the safe arrival at Montreal of the airship was communicated by a Sun man to IYA, and the stations broadcast the announcement. ALL ABOUT VALVES An interesting booklet dealing with Philips valves, in which their characteristics and suitability for various receivers are described, has been issued by Philips Lamps (N.Z.), Ltd. A free copy will be sent to radio listeners on application to Philips Lamps (N.Z.), Ltd., 611 Dilworth Buildings, Auckland. WELLINGTON “MUSIC WEEK.” "Music Week” is being held in Wellington this week, and 2YA is on the air each day from 12.30 to 1.30, in addition to the usual hours. No "silent day” will be observed by 2YA today.

SWITCHING ON

RIGHT AND WRONG WAY Switching on and switching off, although simple to do, can be done in a right and a wrong way. In the case of sets which obtain their supplies from batteries and a filament accumulator little harm is done whatever way a set is switched on. Even so it is wise to switch on the high tension supply first and then the filament current. By doing this any sudden surges in the receiver are avoided, for the filament takes an appreciable time to warm up and, so to speak, turns on the anode current gently. In switching off it is best to turn oft the filament first. The procedure of switching on and off in the case of mains driven sets is more important. Sets of this type have a so-called power-pack. It is a collection of fixed condensers and wire-bound chokes built round a component that changes alternating cur rent derived from the mains into direct current for the valves. When the filaments are all alight the high tension voltages are correct for the particular valves in use. Moreover, the condensers in the powerpack are more than capable of stand ing the electrical pressure generated. When the filaments are out the anode load is suddenly removed and the voltage rises on the anodes of the valve and therefore across the condensers i in the power-pack and elsewhere. This i rise of voltage may be several times j the normal running voltage, rising at | times into four figures. In some cases the condensers are j unable to stand up, and the result is i a punctured dielectric and a "dud” set. I Also any sudden stopping or starting j of a flow of current in itself will tend j to generate enormously high voltages ■ in a choke. It is thus wise to turn on the filaments first in a case of this type and j to turn them off last. By doing this 1 high voltages will be avoided because ! the valves are ready to take the load j when the set is first turned on and I the high tension supply is not there to 1 cause trouble when the filaments are j turned off. ‘ Understanding the wiiv and where- ; fore of details of this type make all the difference in the life of a receiver ! and as a result in the cost of upkeep. *