NOTES AND COMMENTS

Radio Record, Volume I, Issue 52, 13 July 1928, Page 8

NOTES AND COMMENTS

(By rf

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I UNDERSTAND that the P, and 'T. Department has not enough radio inspectors to comply with the Wellington Amateur Radio Society’s request for a house to house inspection of receiving sets, to ascertain whether those which are designed to be neutralised are really neutralised correctly. "Basso" (Kelburn) writes: "The Wellington municipality has a very fine city organ and a highly qualified organist, who plays to a mere handful of people every Sunday night. I am afraid the publie regard these Sunday night concerts as too highbrow, but what is wrong about broadcasting an organ item every Sunday night, so that the citizens who happen to be radio licensees can hear their own grand organ?" ‘A FRIEND was telling me the other day that he had purchased one of the new super-power valves, but he was dissatisfied with the results which did not come up to expectations. I queried him about it, and elicited the fact that he was employing only 6 volts filament current, although the valve was designed for 73 volts!- You ean’t get the best results unless you follow the manufacturer’s instructions. "QOLDER" {Palmerston North) writes: "I have been looking over constructional details for building a television receiving set, published in an American radio magazine. Is there any possibility of television broadcasts from Australian stations within the near future?’ No suggestion of such a possibility has appeared in the Australian Press. So far as this part of the world is concerned, television is 2 very long way off. " A RB automatie controls of filament voltage in a radio set completely satisfactory?" queries "Rheo’ (Wanganui). The best makes of these automatic controls will be found to be thoroughly efficient, but great care should be taken to purchase controls which are manufactured for the valves in use. These controls are designed with yarious characteristics. i | HAVE been thinking of sending to a Pennsylvanian company for aluminium shielding for my homebuilt set. Do you consider aluminium efficient for that purpose?" Shielding of that material is used by many of the leading makers throughout the world. ‘ Two Wellington listeners inform me that they have picked up the Palmerston North stations on occasional nights. One listener operates a fiveyalve neutrodyne set, and the other a six-valye tuned radio-frequency set. WELLINGTON radio company is ‘importing the complete uaits of the electro dynamic cone loudspeakers without the valve amplifying section. The ordinary multivalve radio set can give good amplification under the above conditions. These speakers, fitted in a handsome cabinet, will be retailed at about eighteen or twenty pounds. Hyeryone I have met who has heard an electro-dynamic !oudspeaker declares that it is just about the last word in tone and volume. BVDPRAL listeners have asked me where they can find the Japanese stations on their tuning dials. JOHIX is just below 4QG, Brisbane, and JOAK occupies a similar position with respect to 2BL, Sydney. A RADIO acquaintance confidently assured me that the electrical interference so widely experienced around Wellington was due to the «lectrical plant on a certain steamer then in port. When the vessel lefts port and was some 120 miles from Wellington the electrical interference was worse than ever! "HAYS you any record of the year in which the exponential horn was first brought out and who was the inventor?’ asks "Melody" (Masterton). "Why is it called ‘exponential’?’ As far back as 1924 two American engineers evyolyed the exponential. horn. They were Messrs. Hanna and Slepian, This type of horn, however, was not developed for radio purposes until some years later. It is called "exponential" perause any particular crosssectional area and its corresponding distance from the small end of the horn are related by 4 mathematical equation containing the quantity (2.7 approximately). The more slowly the horn expands, the fleeper the note with which it can deal, provided the area of its mouth is suflitient to prevent back reflection of the sound waves. [THE other night we heard an announcer state that the band would play a certain item, but, behold, the pand played something widely differont. Now, why can’t the announcer snd the bandmaster get together between items and agree as to what is to be performed. If they can’t pgree let ‘them toss for it, 4

SAw a radio’ set lately of a hitherto unknown make in New Zealand, which the owner had imported from the United States, He thought he had a wonderful bargain until he endeay--oured to reach out for the Australian stations. A radio doctor was called in and he convinced the owner that the components in the set were "cheap and nasty," so that it was impossible to obtain even fair results under the most favourable conditions, The audio transformers were of the 1924 vintagecheap material and out-of-date in design, WO inventors in North Wales have patented a combined clock and loudspeaker. Well, we have heard some voices on the radio which would stop any clock. Personally, I prefer to have my clock separate from the loudspeaker and beyond striking distance of it. "THE same old question. " ’Phones" (WKilbirnie) asks: "Do you think there is some advantage to owners of large sets for 2YA, Wellington, to observe a weekly silent night? I contend that there is a substantial proportion of listeners who look forward to the silent night.’ Undoubtedly it is an advantage to operators of multivalve sets who experience difficulty in tuning out 2YA. In order that both listeners shall have an opportunity of reaching out for distant transmissions, the Hamburg station, in Germany, is regularly observing a "silent night," as it done by stations in America. RUBBER and sulphur are the only materials which should be used when ebonite is required to have high insulating properties. The lower grades of ebonite, which have given, and still are causing, trouble to set manufacturers and constructors, contain certain mineral "fillers," reclaimed rubber, rubber substitutes, and ebonite dust ground from scrap in which particles of metal are often present. Even coke and coal dust have been used by unscrupulous manufacturers, A LOUDSPEAKER which issues a slight ringing or blur on certain notes should be examined for loose nuts or screws. A high-class speaker came under my notice recently which was guilty of this peculiarity, An examination revealed a loose nut, which was then tightened up. Within a week the speaker was at it again. This time the nut was smeared with a little sec-, cotine and then tightened up. It has stayed put now, "(COLLEGIAN" (Petone) writes: "I have a two-valve set which includes one stage of audio. I want to get the Australian stations on the headphones. Which do you adviseanother stage of audio or a stage of radio-frequency amplification?’ If my correspondent desires to add another. stage to obtain distance he should adé@ a stage of radio-frequency. ALTHOUGH the art of television is not a new one, as compared wi its sister science, radio telephony, & has been-dormant for many years, while radio telephony has increased in scope with leaps and bounds. Television in the laboratory was an established fact many years ago, but the physical, electrical and mechanical difficulties of bringing it out of that stage Were so many, and so seemingly unsurmountable, that it was only recently that several improvements in the art.were announced, and interest in television received a great impetus, {VEN the slightest crackling of paper held By speakers before the mike has been eliminated in the studio of KI, Los Angeles. The paper ig pasted on cardboard, and each sheet handled without the erackling that has been found to interfere with proper broadcasting.

HEN connecting your loudspeaker fo the set be sure (unless a filter circuit is used) that its red terminal is joined to the terminal on the set, which is connected to H.T. positive, (If this is not done there is risk of serious damage to the loud speaker). THE British beam system of wireless telegraphy has broken the world’s records for long-distance telegraphic communication, by exchanging messages for hours on end at a speed of -400 words per minute, with reception too clear for repetition to he necessary. THE League of Nations headquarters at Geneva, Switzerland, will soon be able to telephone to Washington, Havana, and Ottawa. Switzerland is to become 9, part of the trans-Atlantic radio telephone system almost imme diately. The Cuban and Canadian representatives of the League Council ‘ean then discuss League problems with the home Government by telephone, while the League may also talk to Washington on questions like disarmament, in which the United States is collaborating, , | GTATION 2H, the short-wave transmittee of A. H. Grebe and Co., Inc., of New York, which began operating with 250 watts power, simultaneously with WABC, has been raised to 1000 watts. The station has «lready been reported by listeners as far distant as Trieste, Italy, The wiuvelength used is 58.5 metres, Aé first the station was operated on 62 metres in experimental broadcasts. The shortware station will now be employed with WABC for all programmes. WHEN panels beve beon repaired, unwanted holes carefully filled in, etc,, 2 good overall finish taay be given by smearing the panel with a Inbricating oil and rubbing well with a piece of fine sandpaper in a circular motion. If the sandpaper is not fine scratches will result. A circular movement will give « better finish than backwards and forwards. Alternatively, fine emery powder ani a well-oiled, soft, non-finify rag mag be used fustecil. Vinisi. with a good rubbing with a Clean rag and © perfectly flush and smooth: pouel having a dnli gloss will reste. HERE are still several fields of reseavel: in wireless unexplored, and the future may holi some = surprises, The channels or wavelengths that would be utilised for communicating with portable sets are the ultrashort wavelengths of the order of, say. ten metres and under. These regions in the electro-magnetic spectrum of frequencies are being examined ciosely and continuously o2 late, and additional useful information is being aseertained, but it is unsafe to say that there is any encouragement provided for the prophets who foresee the early arrival of mininture and portuble intercommunicating outfits, UTHORITY to construct the most modern high-power broadcast station in the west has been granted to KNX, Los Angeles, California, the "Iovening Express" radio station, by the Wederal Radio Commission. A 5000-watt transmitter is now being built in the east and will be dedicated to the radio audiences of southera Califo1.ia and the entire west within a very short time. The new equipment will embody the very latest developments in modern radio broadcast, ‘and is expected to be heard at almost inconceivable distances. Listeners wilt be able to inne KNX with an ease never before possible, and the entire continent will be brought cioser to Los Angeles and Southern California, THE reason that am aceumuiator (wet A battery) appears to have two different capacities or rates of discharge is that there are two methods of discharging it. These two methods are: (1) continuous discharge, and (2) intermittent discharge. When used for wireless purposes the discharge is continueusthat is to say, that there is a steady drain on the battery from the time the set is switched on until the time it is switehed off again. Under guch cir cumstances the battery has a far more arduous duty to perform than when it is used intermittently for coil ignition of a motor-car, or similar very short period discharges. In the latter ease when a current is taken out of the accumulator for a very short tine, the long rests between the discharges enable the accumulator t recuperate in some degree; and, consequently, its capacity to yield current is considerably greater when this current is taken in shorr discharges with long periods of rest between, than when it is taken in one long continuous discharge, A & matter of fact, about twice a3 much current ean be got out of a battery when if is discharged intermittently as compared with when if is discharged continuously. So that if your aceuranlator is rated at, say, "twenty" actual ampere hours and "forty" ignition, it means to say that when used for a continuous discharge, such as wireless, if will only yield one ampere for twenty hours, or two amperes for ten hours, but if used for short interraittent discharges almost double the amount of current could

(YARTHAGE, the ancient rival of | Rome, now has ‘a broadcasting Station working on 1850 metres. »s TPUHE Chinese Government has recently opened a broadcasting station at Tientsin, near Peking, which works on a wavelength of 480 metres. [Te pays to test the voltage of the gridbias battery occasionally, as insufficient grid-bias means a heavier-than-necessary drain upon the "B" battery. , Te connect up the different stations in a recent simultaneous broadcast in the United States, over twelve thousand miles of telephone wire were employed. WHEN humming occurs in a set which employs a low-frequency transformer, it sometimes happens that the reversal of either the primary or gecondary leads of this will eliminate the trouble. | T is asseried that during this year the French will erect three superpower broadeast stations, one of which | -already under construction-will have a power of 56,000 watts im the aerial, and will replace Radio-Paris, PF two condensers ef equal value ure eonnected in series, the total value of the arrangement will be half that of one of the vondensers. When two «ordensers of equal value are comunested in parallel, the tutal capacity of the eryvangement Will be twice that of either ef the condensers. T is stated that the Radio Cerpuratien of America and the Film Booking Offive Pictures Corporation are intending to start experiments together so as to try and find a new method of synchronising sound and picture. Several important patents relating to speaking thos, wireless and television will be applied to these oxperiments, IS Majesty the King of Afghanistan has, after several tests, purchased one English 8-zalve supersonic receiver, with a gramophone pick-up and amplifier for the entertainment of his court. These instruments were installel at Cliaridge’s Hotel, Tendon, where the King stayed, and eventually accompanied him back to Kabal. In spite of the short distance from 2L0 Lendon, no difliculty was exrericnced in receiving foreign programmes, and His Majesty expressed bis pleasure at the range of enteriginment available, ERE is an old question. "Batt" (Wanganui) wriies: "Deo my valves wear out the B batteries when they are not lighted? I mean, I jeave my batteries connected up to

the set when it is not in use, and I want to know whether this runs my B batteries down.’ No current drain from the B batteries can take place 1% the filaments of the valves are not lighted. It is better, atall evenis, to disconnect the batteries when the set is not in use, as it has heen found that trouble will develop in the transformer if the batteries are always eonnected un. ey a two-valve set, using detector and 2 low-frequency valve, the ordinary power valve is usually quite sufficient in the last stage; but in a three ox more vaive receiver, if you require big volume, then a super-power valve is necessary. It should be remembered that "super power" dees not mean that the valve will provide a "super-signal strength" or that it has a big magnifieation factor, because this is actually small; but it signifies that it will carry a bigger volume than the ordinary power valye, and unless a valve will earry the volume supplied to it without distortion. hopeless results will he obtained. , HE lower npedance of a superpower valve heips to bring out the bass notes pruperly, and this is especially noticeable if a first-class loudspeaker is used, Also, the long, straight portion of the «haracteristic curve available enables larger grid swings to be dealt with. It often happens that @2 power valve can carry the majority of the volrages imposed upon it, but gets overloaded occasionally when certain notes are played ov certain instruments are used. With a super-power valve there is a greater margin for this kind of overloading, and eonsequently the reproduction will often be distinctly snuperier to that in the former case.

FoR perfect reception, keep the aerial away from trees and roofs of houses, keeping it as high as possible, not too long (about 100 feet, including the lead-in, is admirable. Do not solder a lead-in to the aerial wire, but take one wire for the aeriql, and continue it straight to the set. Keep both lead-in and earth lead insulated, and as short as possible. In dry weather, if the earth is buried below the ground, pour several buckets of water over the spot. Keep dust away from the set, hy keeping the lid of the cabinet closed, and absorb all moisture by keeping a small piece of chloride in a corner of the cabinet, Keep all leads in the set as short as possible, particularly those of the grid and battery, and, above all, don’t try to work of an exhausted "R" battery,