THE MAGIC SPARK.

Auckland Star, Volume LV, Issue 169, 18 July 1924, Page 12

THE MAGIC SPARK.

VALVE QUERIES. GROWING RADIO INDUSTRY. GRAMOPHONE RECORDS WIRELESS. LOCAL NEWS. (By PHONOS.) The concert broadcasted by the Lyric Four this week provided the'most enjoyable entertainment that has yet been put on the air from Auckland. Appreciative references as to its quality have come in from many quarters during the past two days. The sealed set system adopted by Australia after a study of wireless control as conducted in other countries, is now a dead letter. For some time the regulations governing (he sealing of sets have been ignored and now the whole question of regulation of wireless in our neighbouring Dominion is in the melting pot. The one satisfactory aepect of the whole subject is that New Zealand did not follow Australia's lead, which was heralded, at its inauguration, as a model for other countries to copy. Decidedly encouraging entries for the Radio Exhibition have already come to hand, though the closing date is not until the 26th. In addition to displays \ in competitive classes, examples of most recent radio developments will bo displayed, lecturettes will be delivered, and practical experiments and demonstrations appertaining to wireless matters will be given. The Northland Radio Society, Kaitaia, which has a membership of over ISO, has been admitted as a sub-branch of tho Auckland Radio Association, and has been requested to nominate a representative on the executive of the latter body. The judges for competitive classes at the Radio Exhibition to be held in the University buildings next month, arc Messrs. G. Salt, M.A., M.Sc, of the Auckland University; E. R. Green, M.Sc, of the P. and T." Department; and C. M. Taylor, science master of the Grammar School. The next informal discussion arranged by the Auckland Radio Association will centre round a lecture on the "Theory and Construction of the Xeutrodyne," which will be delivered by Mr. J. M. Bingham, A.M.I.R.E. PHENOMENAL RADIO TRADE. We in New Zealand liave no idea of the magnitude of the radio industry and of the almost unbelievable advancement it has made in the present decade. The figures quoted below are from official sources and are staggering, but they indicate that the production of radio apparatus has developed into one of the main industries of U.S.A. According to the latest figures available the total radio sales for 1023 amounted to £50,000,000. This is a tremendous total; and the indications of the past half year were that 1924 would total over £80,000,000. These | figures only cover three million receiving outfits, whereas it is estimated that U.S.A. has a potential market for at least 25 million sets. No wonder some of the more ambitious radio magazines published in "America can carry over 100 pages of advertisements an issue. I AN INTERESTING QUERY. j A correspondent inquires: Can any circuit be used for both dry cell and storage battery tubes? Is there any circuit designed chiefly for dry cell tubes ? j Why is it that WD-12s and UV-1099 ' operate better as detectors in circuits ' which utilise a tickler feedback than in those which tune the plate circuit ? What is the effect of increasing the plate voltage on a UV-201-A to HO volts? Does the increase in signal intensity justify the increase in voltage 1 Any circuit which is designed for operation with the three-element vacuum tube is adaptable to either dry cell or , storage battery tubes. The variation in operation of WD-12s and TJV-199s as ' .. detector* in various regenerative circuite Iβ due to the internal capacity between the grid and plate. In circuits which utilise a tickler feedback, the regenerative effect is obtained by I means of this feedback, that is, feeding Home pf the energy from the plate circuit back on to the grid of the tube. On the other band in circuits which utilise a tuned plate system, the regeneration is due to both the bringing close to resonance of the plate and grid cirpuits and to the reactionary ''effects of , the capacity between the grid and plate inside of the tube. In the case of the above-mentioned dry Cell tubes this capacity is small, approximately half of that of the 201-A, and when th@ circuits are tuned to the higher wavelengths this value of , capacity is not sufficient to allow the , proper feedback through the capacity. , It is for this, reason that WD-12s function well in- grid and plate variometer receivers when the , variometers are tuned | to wavelengths less than 400 meters. < In some instances, however, these tubes J functioned well on all wavelengths, but th,is effect was due to some inductive feedback between the variometers. , The. effect of increasing the plate volt- ] age on a 201-A to 140 or 150 volts is , indeed marked upon the "B" battery, j that (» the life of the batteries. This increase of 50 volts from 100 to 150 , practically doubles the plate current | j drain. At the former value the plate | current drain (without "C" battery) is j 7-f» mils —when the plate voltage is in- ( creased ito 150 volts the plate current , value rises to almost 15 rniliamps. In addition-distortion will invariably result , if the proper ''C batteries are not used. ( The increase in signal intensity obtained j when the plate voltage is increased to the above value dope not justify the cost; ' of the additional batteries nor their de- , crease in life. . LOUD-SPEAKER RECORD. \ What was believed to be the first { gramophone record to capture broadcast 1 music was made by Mr. R. Sedgwick 1 Willq, an English engineer, who, after i several months' attempts, made for experimental purposes a record which was i not only comparatively clear, but almost 1 as loud as the ordinary record. It was I made by means of a loud speaker with c a specially constructed diaphragm which s he designed himself. 1 Mr. Wills' record, which measures 18 1 inches across, captured the music of the i Savoy Orpheans Band playing at the a Savoy Hotel, London, about 170 miles distant from Exeter, where the record a was made. r Mr. Wills took his record to the Savoy j Hotel for the Orpheans to hear, and for I the first time that band heard" them- a selves as they are heard by millions of \ listeners-in. c The record had an untimely end, how- t ever, for Mr. Wills, on visiting Lojjdon, b found that he had cpminitted a legal t irregularity by makjng the record, and c h? destroyed j t t f ter t he hand Wd it.