NOTES AND COMMENTS

Radio Record, Volume I, Issue 42, 4 May 1928, Page 8

NOTES AND COMMENTS

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8 ie is., less than, one hundred years ‘+ since Michael Faraday discovered » electro-magnetic induction between two : entirely separate circuits. ACCORDING to the London ‘‘Police Journal," wireless is playing a great part in the inter-commimunication of police forces in Iingland and on the Continent. ANOTHER remarkable proof of the : efficiency of the British broadcasting servicé is provided in the annual ; breakdown statistics of the British broadcasting corporations, ‘The combin':ed British stations in 1927 had 65,299 ' hours of broadcasting fixed for them, ; and of this: time only 0.03 per cent., or ; ‘aboit-19} hours, was lost through break- + down. Spread over the 20 stations being operated; ‘this: represents the loss ; of about one hour-a year for each staition through ‘breakdowns. In 1926, the "percentage, of time lost through break- ‘: dowhs ‘was 0,07,.per,cent. of the tezal broadcasting time, while the year before it was’ 6.09 of the broadcasting ; time... The , British. longwave station, » PXX, at Daventry, was the most con- , Sistently used,. broadcasting for about ' 5000 liours in "the year with only 0.07 of this time lost through breakdcwns. -.. The London Station 2L0, which trans‘mitted for 3560 hours.with a breakdown . time loss.of only. 0.02 per cent., or + -about 40 minutes in:the year, was nest. gent APTER you have built .a° set if you , 2". havea valtmeter available take a v. Yeading. of,,the voltage between the two .. -filament, coptacts of your sockets bex fore placing any, valves in the set », .While it may. be true that you have ex_vercised, the :greatest care in building and checking oyer your set, the high voltage B battery wire may be crossed !. with one of the, filament‘ or ground '-» wires in suchya.manner as to place 22} aor: 45 volts across. your filament. con‘ui: nections: instead: of the. customary J; » or 6.yolts-of:A battery. To test simply .: touch -the: two terminals of your volt- ‘ meter to the two. socket contacts and note what reading the meter gives. It .. the B battery voliage has been placed on the filament terminals of your socket you will be quickly advised of the fact by.the high reading of the meter. . "PHE. London Metropolitan Fire Brigade adopted Marconi wireless signalling in 1900, and apparatus was fitted at Mitcham Lane and Streatham Fire Stations, London, S.W. ! ‘ n "t ‘ a + . TPHE only. satisfactory way of choos- . ing. a loudspeaker is to hear it working upon your own set. v whicl! accomplishes the journey ‘between these two cities in seven hours * and a yuarter instead of the usual time ‘* of over nine hours, has now a special coach which is ‘equipped with a recciyer ‘ "and picks up broadcast programmes for ' ‘the entertainment of passengers. About sixty pairs of headphones are provided at present, and it is proposed that the _.. system should he extended to all firstclass compartments. An _ interesting technical point is that, once the train has moved outside the clectrified area of the traction system, the reception is »+ very much improved. WING to the acid getting on the terminals of an accumulator (wet battery) corrosion frequently occurs here. It may be prevented by smearing the terminals all over with vaseline. It is a good plan to put a little vaseline on any of the exposed metal parts of a wet battery cell such as the counecting pieces between the cells. AX ‘IOUGH there are no broadcast- : ing stations in Rumania, it is officially estimated that there ar: 15,000 owtters of receivers in the country. They rpuE new Paris-Bordeaux express, we . 4 rely for, their entertainment on pro--grammes from Russia, Poland, CzechoSlovakia, Hungary, and Jugo-Slavia. ACCORDING to reliable statistics recently prepared, Germany exports more witeless apparatus than any country in .the world except the United States. POWERFUL broadcasting stations are being erected at Genoa and ‘Turin, to replace the existing stations. : [STERESTING plans. have been made to use wireless telephony for sig- ‘ nalling purposes at the Victorian Light . Car Club’s 100-mile race, to be held on Phillip Island. ‘Iwo Melbourne ama- . teurs, Messrs, H. T. Simmons and M. : Chaffer, will have charge of the apparatus, which will consist of two portable ’ transmitters and receivers. One of the sets will be installed at the finishing : point of the race, and the other will ' be placed at the farthest point on the course from this point. In this way officials conducting the race will be able to communicate over the main portion of the conrse. The sets to be used will be very simple, but they will be capable of working ‘duplex’’-that is, ‘ communication will be possible with out the need for the changing over of the actial from transmitter to receiver which is familiar to listeners to most of the amateur stations. Power to operate the transmitters will be supplied by receiving high-tension batteries, pus old -British battleship ‘Centurjon" has been fitted with a wireless transmitter that can steer, start, ‘ and stop the ship, so that she can be mansenyred from a distance by radio.

JUXPERIMENTS ‘in’ short waves are interesting’ quite ‘a * considerable number of .French amateurs; and’ one of the latest ‘to produce’ a’ new: Short wave circuit is Monsieur Braleret. This well-known Frerich’’ experitnérter’: has produced a new ‘circuit which’ he claims facilitates very greatly ‘highfrequéency — _amplification on short waves. ‘He, has been giving demonstrations ‘twit? 4 week for some time’ past;’arid has‘ sate isfied a number of well-known ~atithori+ ties of the efficiency of his new circuit. Ww HUREVER you use an insulated y wire, especially cottomcovered wire or woven itsulation, wind -a «strip of insulating: tap around the end of! the wire to prevent the covering from working loose. A short length of ordinary wrapping twine will do just as well, and may eyen ‘look a bit-better tham tape. This will improve the appearance of your radio set a great. deal and may even repay you for the time+you have taken by preventing two wires front accidentally ‘shorting’? sometime, . Bat tery connectors which dre subjected to considerable twisting and bending should be treated in this way to pres vent the ends of the insulation working oose. PANS te. continue the’ nation-wide effort toward: stabilisation in, the radio industry were atiounced in’ New York lately by the American Engineers ing Standards Committee, , coincident with the election of Dr. A, N...Goldsmith, president of the Institute of ’Radio Engineers, as.chairman of its conmittee on radio standardisation. One of the aims of the committee is to. pros duce new radio designations, which. wilf be ‘informative and helnful to the public." . "PELEPHOTO pictures of the Holly wood, California, participants 1 the Dodge Brothers’ radio programme commencing at 10 p.m, on , March 299 over a national chain of stations, were sent out from that city to eight "key cities’ of the United States ims mediately. after the period .on the air. The pictures were available within. an nour and a half after the broadcast. — >

‘To obtain the maximum service from dry "A" batteries, the rheostat must be lett in the ‘‘off’ position when the set is not in use, or the batteries should be disconnected entirely. ‘The rlieostat should, in use, be coutrolled to keep the current as low as possible. Do not use miore battery current than is nécessary-in other words, turn up your filament rheostat only enough to get good results. As your "A" batteries get older, it will be uecessary to turu up the rheostat further. TR® new shielded-grid valve greatly resembles, exterually, one of the ordinary 201A type; it is of about the same diameter, but slightly longer. It is equipped with a standard four-prong vase, the fifth connection being made to a small brass cap, which is mounted on the top of the glass bulb. The glass appears to be partially silvered on the inside, as do most valves, ‘because of certain chemical treatments which they undergo during evacuation. A NEW series of high power two- | way transoceanic television tests by short-wave radio will be started soon between Newark, N.J., U.S.A., and London, England, according to Captain Oo. G. Hutchinson, managing director of the Baird Television Development Company of London. Captain Hutchinson announced the new tests in New York recently, just before lis departure aboard the Berengaria for UEngiland, where he was to "confer with John L. Baird, the inventor, and make further arrangements to continue the 3600-mile experiments. ‘After spending a few days in London, I will return to the United States with Mr. Baird," he said, "In the meantime, arrangements in America for the coming tests will go on as tisual."

T° obtain the highest possible efficiency when using the new valves of the shielded-grid type, an external shield must be placed around each stage. ‘This is found necessary in order to avoid oscillations, aud to obtain maxiul amplification. WHEN using mote than 45 volts of "RB" battery, the addition of a "CG" battery will add materially to the life of the ‘Bb’ battery, and usually result in better reception. ‘This battery is connected between the filament and the grid, and it reduces the amount of plate current, and, therefore, increases the service-hours of ‘‘B’’ batteries. The "C" battery should be conuected at the negative of the ‘‘A’’ battery, in many sets between the filament lead on the (-) of the "A" battery to the ‘Ll’? post of the transformer. When power valves are used, it is particularly necessary to keep the current drain as low as possible by using the proper high voltage "C"’ battery. T* the reception of distance stations it often happens that the signal will fade out completely only to return a moment later. This happens without touching your dials or moving your position. This is particularly annoying at times when you are enjoying a good programme or are trying to intercept the call letters af the station. ‘The trouble may be due not only to unavoidable atmospheric causes, but also to a low A battery or a dirty contact in one of the valve. sockets. In either case the valve will light up bright for a while and you can hear the station plainly, The next instant the contact may be poor or the A battery voltage will drop slightly and the station will completely disappear only to return a moment later when the voltage comes back to normal. SOME of the English newspapers are proue to give the utmost publicity to any edverse criticism of the British Broadcasting Corporation, which provides probably the finest service in the world. A writer in the London ‘‘Modern Wireless" says: "If piffling Percy Puggins of Biggleswade, having invested in a three-and-sixpenny crystal set which he is mentally incapable of understanding, finds himself one evening totally unable to hear anything from London or Daventry, piffling Percy immediately writes to one of the newspapers and asserts that the B.B.C. is governed by persons of an unintelligence that is beyond belief. The newspaper immediately places piffling Percy’s complaint in a prominent place, causing that fool to go about with a swelled head for the best part of a fortnight,"

, e PSE Berlin Voxhaus broadcast station transmits generally on a wavelength of 462.9 metres, corresponding to a frequency of 620 kilocycles. Its normal power is of the order of four nilowatts, the station generally transmitting a morning, afternoor, and cvening programme, the latter ending approximately about 12.30 a.m. Although its power is not over-great, the station possesses good transmitting characteristics, and it can generally be picked up all over England, using, under suitable conditions, a threc-valver of normal efficient design and construction. The Berlin Voxhaus specialises in orchestral music. ic has made a special study in this direction, and whilst its regular orchesira has a normal memnership of nearly fifty performers this number is very frequently augmented for special concerts. A STRIKING proof of the importance . of absorption in wireless reception may be gained by the city listener if he tukes his receiver to some country position. He will find an enormous inetease in the signal strength of all the distant stations he could hear in the city, and in addition he will generally hear stations that could never be heard in the city. The reason for this is that the buildings, telegraph lines, and cleetric light lines of the city have a marked shiclding effect, which greatly reduces the intensity of wircless waves near them, This is why country listeners obtain better reception than those in the citv. TPE pioncer American — station KDKA has been experimentally sending out transmissions on 2.5 metres but has now abandoned this wavelength as being too low for practical purposes,

PLAtr buckling in a wet battery is not so common a tronble as sulphating, and is usually due to the eclls being charged or discharged at too high a rate. The heat set up in the cell causes the plates to warp or buckle owings to the expansion of the metal, due to the heat. Buckling has a tendency to loosen and dislodge pellets of paste from the plates with the risk of a short-circuit oceurring between adjacent plates. TRH internal resistance of an accumuuator (wet battery) is very low, so small as to be negligible for most purposes. If by any chance the — terminals of the cells should accidentally leeonie short-circuited, a very heavy enrrent will flow through the battery, and, if the short circuit continues for more than a moment, will quickly canse damage to the plates owing to the heat generated. Kvery possible care must therefore be taken to prevent a sbhertcirenit occurring, N&#VER work om your set with a setewdriver or a pair of piiers when the valyes are in the sockets and your battcrics are all connected, ‘The -mnain reasons against this practice are that you may accidentally drop a tool on top of a valve and break it or you may short the plus B battery lead with one of the filament wires, "PH shortwave service of 31,0, Mel- * bourne, is listened to regularly at Rereclona, Spain, by Don Tunis de la Tapia, and it is interesting to note that in the issue of "La Vangaurdia,’"’? published in that city on January 24, the following paragraph (translated in Iinglish) appeared -- "Our subseriber, Don Iuis de la Tapia, well known in the wireless world, advises shaving heard on 32 metres between 19,00 and 20-30 on Sunday, 22 January, a programme from Station 8LO Melbourne, 20,060 kilometres distant fronr Barevlona, with a two valve reesiver.’’ PAL proof of the growing interest in shortwave broadcasting is provided from Aierica, where the Ratio Corporation has perfected a new shot'twave rcceiver of the well-known "Radiola" series, for use by amateurs. This recciver, which uses four valves, one of which is the new "screened grid’ valve, is claimed to give good loudspeaker reception from all the highpowered shortwave broadcasting stations in the world, NE of.the great American rubber importers keeps in touch with his plantations in Nigeria, Africa, by means of shortwave wireless,