RADIO NOTES

Dominion, Volume 26, Issue 103, 25 January 1933, Page 6

RADIO NOTES

By

"ETHER“

CURRENT TOPICS A writer in the “Radio Times” recently had the courage to suggest this to the 8.8. C —that its monopoly is acting .as a brake on the full development of radio broadcasting as a uew art. Bis reasons are specially interesting to listeners residing in the provinces. He pointed out that monopoly limits the number of programme-creators, and that German experience seemed to confirm this, for there the existence of nine independent stations has stimulated the production of radio plays to the amazing figure of eight hundred a year. Xt * * Whether the.rivalry between stations in Germany has similarly stimulated other, departments of broadcasting—music,. talks, outside relays—is not dear, and seems less likely, but there is no doubt that the German arrangement of nine different directors of programmes with nine different notions of programme-building has its merits.

The recently celebrated fifteenth anniversary of the formation of the Soviet regime coincided with a decision to develop the musical and dramatic side of Russian broadcasting. The uew intention is not. entirely unconnected with an ofllcial order that radio must soon “pay its way” by means of ■listening licenses. Evidently it is felt that Russian listeners can only be induced to pay up if the programme fare is attractive.

Although the radio authorities have neither finalised the date nor the place it is a sign of the times that they have made arrangements for Dame Sybil Thorndike and her company to broadcast again. This time the complete play of the “Merchant of Venice” will be given. Every effort is being made to make this play available to every .part of New Zealand. ‘ Provided that arrangements can be made to use the telephone lines the play will be fed to the four main stations if not. to some .of the smaller relays. The play is beihg done specially for the Broadcasting Board in one of their own studios and not in some public hall. It is anticipated that nearly one and a half hours Will be required. In this connection ■ it is a bold break away from the short potted variety of playlet that has so long monopolised radio drama, TWO LOUDSPEAKERS Trend Toward Dual Units THE EFFECT DISCUSSED In view of uncertainty concerning the latest idea of using two loudspeakers, the following opinion of an expert writing in the “Wireless World” is of interest. He says:— There are at least three schools of thought about dual loudspeakers, and their various advantages can be described. One is a combination of electrostatic and electrodynamic speakers. The former is well able to stand by itself and is very good in the middle and upper register and in the reproduction of transients, but the moving-coil speaker will give better reproduction of the extreme bass. Secondly,.we have the possibility of using "matched pairs” of nearly similar moving-coll speakers. This has much to commend ’it, for it is a cheap and not-too-difflcult business to have two cones of such substance that where a resonance occurs iu one we have a dip in the response of the other, when the two together will give something approaching a straight-line response. It should be remembered, however, that the total frequency range of the pair cannot be greater than that of either of the speakers taken separately, and that the putting together of two identical units or of two chosen at random is useless. The generalised statement that two loudspeakers are better than one is fiction; they must be designed specifically for that purpose. Finally, there Is the plan of using two moving-coil units of entirely different design, one of which looks after a portion of the frequency range and the other reproduces the remainder. With this method a wider frequency range can be covered than by any other means.

There is the necessity of keeping bass out ot the treble unit and treble out of the bast unit, which calls for filter circuits which add to the cost. The resultant pair will,, however, handle an enormous input, so that the cost per watt of power-handling: capacity is likely to be lower than of a single unit. AVOIDING THAT HUM. Some “Don’ts” for Sufferers Keep the aerial lead-in wires well separated from the house-lighting and power wiring, and don’t stand a reading lamp near the set. Don’t run an amplifier or receiver extension leads parallel with or near lamp wires and other wiring connected to the mains. Don’t place the set near the house wiring or circuits connected thereto. Don’t run long battery wires to either the low-tension or high-tension batteries down through the floor to the cellar where they may come near the electric power meter or wiring. Don’t place any kind of eliminator too close to the set, either above it, below it, or at the back of it, unless .the eliminator is contained in a completely shielded and earthed case. Keep the mains transformer, the output filter choke, and the first-stage coupling unit the correct distance apart —follow the design of a mains set in detail. RADIO IN CARS In making a radio installation in a car, it is always well to look over the car wiring and make certain it is in good order, also that the breaker points are clean and have a fiat surface, and that the generator brushes and commutator are in good condition, says an English writer. Shielding the spark plug wires is not recommended. It is expensive and the results obtained do not warrant it. Tight: shielding adds considerable capacity to the system. This capacity must be charged and consequently absorbs energy from Hie coil. This will be noticeable by hard starting. In oars equipped with a magneto this rule does not apply. Rubber-covered high-tension wires should never be shielded as corona trouble and leakage will soon be experienced if tight shielding is used. Where it is necessary to shield a hightension wire, varnished cambric-covered wire should be used. This wire can also be had with metal shielding $1- : eeady on iij,

TESTING YOUR SET Pieces That AVill Show Up Weaknesses A LIST OF RECORDS Searchers after perfection in the audio response of their radio set might find it. instructive to acquire tile following records, or some of them. They have been specially selected for the purpose as indicated below: — Tests of Good High Frequency Response. Wagner: Maestersingers Overture, especially the Homage to Hans Sachs theme for the brass. Strauss (Richard) :Almost any of the Symphonic poerns. Borodin: Second Symphony. Second movement. The surge of the strings if particularly good. Tests of Good Bass Response. Beethoven: Seventh Symphony. Second movement. ' Tschaikovsky: Fourth Symphony. Third movement. Dukas: L’Appreuti Sorcier. Cesar Franck: Symphony. Tests of Good Transient Response. Beethoven: Ninth Symphony. Second movement. <g. . Rimskv-Korsakov: Cappricio Espagnolc, especially the last section commencing with the roll of drums. Stravinsky: Petroushka Ballet. Bach: Toccata and Fugue, as arranged by Klenovs|:y. Tests of Piano Reproduction. Tschaikovsky: Plano Concerto No. 1. First movement. Salnt-Saens: Carnival des Animaux, "Pianists.” Test of Violin Production. Beethoven : Violin Concerto. First movement. Test of Individual Instruments and Everything Else as Well. Ravel; Bolero for orchestra. IN BARBER'S SHOP Radio for the Customers INDUCES MORE SPENDING While awaiting my turn in a Czechoslovakian hairdresser’s the other day I was pleasantly surprised to be handed a pair of phones, writes a traveller in an English publication, and I then noticed that each man receiving tonsorial attention was also equipped with phones. Actually each ear-piece was held on a separate arm projecting from either side of the head-rest. In this manner listening could be carried out irrespective of whether the sufferer was being shaved or having his hair cut. When my turn came I was greatly pleased by the comfort of the headpieces, which were fitted with pneumatic cushions to shut out all external sounds and to ease the pressure on the ears, Projecting from the arm of the chair was a convenient volume control knob. ® The set was evidently tuned to the local station, and although I could not understand the announcements, the programme was mainly musical, and I thoroughly enjoyed myself, so much so, iu fact, that when ray hair-cut was concluded I was loath to leave the chair. In fact, I followed up with a shave, although I did not really need one, facial massage, and several other luxuries which ordinarily I do not permit myself. In the end my bill came to a pretty penny. Here was a lesson for hairdressers in this country. I advise them to have their premises similarly equipped, even If only for the sordid motive of inducing their customers to spend more money.

HOME-MADE UNITS New Couplers are Popular

The new coupling units for low-frc-quoncy coupling are becoming very popular. They consist of a transformer with a feed-resistance and coupling condenser. Ton can, however, make up from components already on band, a. low-fre-quency coupling unit which is virtually as good as a commercial one. For this purpose, of course, you will require a low-frftqneney transformer and a condenser and resistance, of suitable capacity and resistance value respectively. The condenser aud resistance are both of the fixed variety. The characteristics of the valve which is followed by the coupling unit will determine the value of the resistance. You will generally find that the best value of this resistance is between two and three times the impedance of the preceding valve, although this value need not be very exact. As regards the capacity of the fixed condenser, a value of .2 microfarads gives best results, |?ut this may be varied up or down; sometimes as much as .3 or as little as .1 wlil give be.ttcr results. Inasmuch as an average value of impedance of a valve will be, say between 8,00(1 and 20.000 ohms, the value for the resistance will vary between, say, .15,000 and 50.000 ohms.

INTERFERENCE BOGEY Root of Present Trouble The electrical industry is one of the best controlled and organised in the country, and the big electrical firms are unfortunately largely responsible for electrical interference, says “’The Wireless World," for the reason that they have been selling, and are s(ill marketing in increasing quantities, electrical apparatus of types which cause interference.

Surely, in their own interests this state of affairs should be remedied, at once. It is. in our view, inexcusable, not to say incongruous, for an electrical firm to lie selling a customer in one department a wireless set, which, given freedom from interference, is capable of a wonderful performance, while in the next department the same customer may buy another piece of electrical apparatus which, if he installs it in his house, can completely mar the performance of the wireless set.

This state of affairs is still more inexcusable when we realise that in very many cases a few pence added to the production cost of the offending apparatus would effect a. remedy.