NEWS AND NOTES

Radio Record, Volume I, Issue 15, 28 October 1927, Page 8

NEWS AND NOTES

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In the case of most good loudspeakers you run a risk of burning out the fine wire coils within them if you employ mote than 96 volts.B battery, unless you use a loudspeaker. output transformer or a choke-and-condenser unit. The siftron and similar devices will prevent damage to your loudspeaker and greatly improve the tone of it. The first regular broadcasting accomplished in Australia stands to the credit of. Mr. Charles Maclurcan, of Sydney, who commenced at the beginning of 1921 to transmit on Sunday evenings on a wave-length of 1000 metres. Jt is truly amazing what has been accomplished in broadcasting during the Jast six years. Some of us old-timers have vivid recollections of the sawmills’? which used to puncture the ether in New Zealand a few short years ago, and they called it "broadcasting." It is often desirable to have a number of wood screws with blue heads for use in mounting the front panel on a radio set. If the blued screws are not handy, they may be ‘easily made by heating common iron screws .of the proper size and screw head ijn an alcohol or gas flame until they have the proper colour, ‘The flame must be one of intense heat and the screw must remain in the hottest part of the flame for some length of time so that the blue oxide may form. iter the propec colour has appeared, the screw may be dropped in a container of water heathy so that it may be quickly coolThe "wonder" station KFON, Long Beach, California, which is heard all over New Zealand from about 5 p.m. till 7.30 p.m., every evening, employs a power of only 500 watts, and Operates on a wave-length of 241.8 metres, This great little station is owned by Nichols and Warriner, 212 Jergins Trust Buildings, Long Beach, California. ‘the station’ slogan is "‘Where your ship comes in." _A spade terminal of a battery cord as tather apt to work loose from the binding post of the set if there is any vibration. A good plan is to bind one prong of the spade terminal forward and the other backward. ‘this gives a spring-like effect which will gtip the binding post more securely even if the thumb-screw top on the terminal works a little loose. Loose battery connections make crackling sounds in the loud- speaker and static is erroneously believed to be the cause. Lack of sensitivity and volume in a seceiving set can often be traced to poor contact between the socket confact springs and the prongs of the valve. Che exceedingly feeble currents passing through the socket must meet with a minimum of resistance, and in this respect perfect contact between the prongs and socket is an absolute necestity. A liberal application of a fine stade of sand paper on the valve prongs will quickly remove any of the corrosiott and bad spots which make for a soor contact. It is sdvisable to clean the prongs at regular intervals. The Chicago committee of the Atwater Kent foundation National Radio Audition has been perfected, and the jate for receiving applications from hhose desiring to enter the national wontest for "unknown radio voices" was txtended from August 25 to September $ The foundation is conducting a na-tion-wide search for radio voices now anknown. The plan includes eliminalion contests 1n towns, states and districts, ending in a national final over Station WIAL’ and a national hookup 1 December. Crackling and other extraneous woises in a radio receiver may often e traced to dirty contacts on jacks. rerfect contact by the various springs b an absolute necessity. Tacks should te given a periodical overhauling, and their contacts carefully cleaned, either by the use of a verv fine file, such as fs used for filing points itu automobile timers, or a verv fine grade of | sand paper. Care should he taken in the nse of the file or sand naner that only the corro:fon is removed from the contacts. If to. much of the material 1s removed, the various springs will not make the proper connection Often some "fan" is desirous of knowing which is the plus and minus of his londspeaker cord tips. Everyone should know that if you connect the cord tips the wrong way round to vour loudspeaker vou are going to damage it by weakening the marnet within it. Some imported radio sets do not bear any indication as to which is the positive or negative of the loudsneaker connections. Here is a method of distinguishing which is which Peel part of the skin off a raw potato Connect um the batteries of vour set, turn on all filaments, take the cord. off your loud. speaker, and stick the tins of the cor into the notata, ‘The nositive tin wt make a Iiue stain on the notato. Then connect that tip to the loudspeaker nost marked with a cross or a ted spot. Three creat inventions nowadavs i vide mass education without cost to t 7 talepaver, They sre, in the ortier ot their discovery and develonment : 1, The apnlication of power to printing processes; 2, Kinematorranliv: 8, Broadcasting. Fach of these inventions, reduced to its fundamentals, to a scheme of magnifiestion Printing machinesv enables millions of peonle to read the same storv at the same time; Pinematy granhy cables millions to see it: hroadcasting enables millions to hear it.

_ The use of a pair of pliers or a knife in skinning a Jength of silk-covered cop: per wire often results in the free en¢ of the wire being cut off. This often necessitates rewinding of a coil. The best procedure for skinning silk or cotton-covered wire is to double over a piece of No. 00 sand paper and draw the wire between the folds. The fineness of the sand paper is just right te grasp the tiny fibres of the imsulating material and will effectively remove the covering. A distinct advantage in using this system is that the sand paper also polishes the wire, which allows it to be easily soldered. Home-builders or buyers of ‘‘cheap and nasty" receiving sets should bewate of cheap variable condensers. A condenser of an inferior quality cannot give good results. A radio authority says: "he losses in a cheap condenser may be summarised as__ follow :-(1) Dielectric leakage; (2) dielectric hysterisis; (3) insulation leakage; (@3) (iirect-current resistance in plates; (5) stray field capacity, (6) insulation hys terisis. ‘hese losses in a good cone denser are reduced to such a point that the most sensitive instruments devised to measure resistances cannot accurately indicate or eheck any losses whatever. This is not an exaggeration,. Yt does not mean, however, that there are nce losses, but that the losses ere so smal} that it is impossible with unusually delicate equipmient to determine them." The little C battery (grid-bias battery) which is now in general favour for ap plying to the grids of all audio-fre-yuency amplifying valves, not only re moves any harshness in tone, but means a saving of about 70 per cent. in F nattery consumption. ‘The positive of 4 C battery is connected to the negative of the A battery, and the negative of the C battery is connected to the fila ment connections of the secondaries o! the audio transformers. The necessary voltage of the C battery to be use¢ varies according to the voltage of_the B battery on the audio valves. Fact make of valve is generally accompanied with instructions as to the amount of ¢ hattery voltage required. Owing to the natural characteristics of the last audio valve in a multivalvs set not "nicking" with the character. istics of the loudspeaker the tone the iatter is sometimes impaired. The tone quality of the loudspeaker cat often be improved by connecting a .008 mfd to a .02 mfd fixed condenser across the loudspeaker cord tips at the en earer the receiving set. A second com. denser of a similar type can also be placed across the londspeaker terminals. New Zealand short-wave broadcast listeners who find that there is much interference when listening to 2XAF, Schenectady, U.S.A., on 32.77 metres, will be interested in the report of @ Melhourne amateur transmittér. _ He says: "There is now such terrific interference on the $2 to 33 metre wave band that quite a number of amateur stations are moving up again slightly, so as to be able to work without interfering with the numerous ’phone and commercial stations that are working there." Cord tips are sometimes subject to 4 fraying in which the fabric around the tinsel works out from within the cord tip. Since this braided covering acts as a strengthening device in respect to the conductor, the cord tip soon breaks loose from the wire if the end of the fabric becomes frayed. If a short length of fine black or brown silk thread is "whipped" around the frayed por« tion of the cord and securely held in place while a liberal coat of flexible collodion is applied, a permanent repair will be made. In fact, such a repair will withstand continuous abuse for @ much longer period than the original type of construction.