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M Apr 1923 .Pdf THE WIRELESS WORLD AND RADIO REVIEW THE OFFICIAL ORGAN OF THE RADIO SOCIETY OF GT. BRITAIN No. Igo9 [VOL.Vo °' XII.I' ] APRIL 77th, I 9 2 3 WEEKLY EDITORIAL AND PUBLISHING OFFICES : on the equipment of the home workshop, The Wireless Press, Ltd., 12 and 13 Henrietta St., describing the tools required in making up Strand, London, W.C.2. apparatus and their use. Mr. W. James, also Telephone : Gerrard 2807 -8. of the technical staff of the Journal, is EDITOR : Huon S. POCOCIi. contributing a series of articles illustrated RESEARCH EDITOR : PHILIP R. CouxsEY, throughout with practical references describing B.Sc., A.M.I.E.E. the principles of wireless telegraphy. Many ASSISTANT EDITOR : F. H. HAYNES. new ideas will be included in early issues, Questions and Answers Department : Under the supervision of W. JAMES. whilst Mr. Maurice Child will shortly com- mence to describe a series of experiments HE EDITOR will be glad to consider for pub- in lication articles dealing with subjects within the wireless, the purpose of which will be to scope of the Journal. Illustrations should pre- build up for the amateur a thorough under- ferably be confined to photographs and rough drawings. standing of the purpose and function of all The greatest care will be taken to return all illustra- components in wireless tions and manuscripts not required for publication if apparatus. these are accompanied by stamps to pay return We believe that readers will appreciate postage. All manuscripts and illustrations are sent the reduction in price of the Journal from at the Author's risk and the Editor cannot accept 6d. to 4d.' per copy. This reduction has responsibility for their safe custody or return. been made possible owing to the large Subscription Rates; 20s. per annum, post- free. Single copies 4d. each or post free 5d. Registered at the G.P.O. for trans - increase in circulation, and it is fitting that mission by Magazine Post to Canada and Newfoundland. our readers should share in the prosperity ADVERTISEMENT MANAGERS; of the Journal. BERTRAM DAY AND CO., LTD., 9 and so Charing Cross, S.W.r. Telephone; Gerrard 8063 -4. A New Transatlantic Achievement. For many weeks past the Editorial post The New Volume. has been overflowing with reports of reception With this issue we introduce to our readers both of American broadcasting and amateur the XIIth Volume of The Wireless World stations. The recent Transatlantic Tests, and Radio Review, and we do so in the too, have shown what is possible in the way ea-nest hope that we a-e including within of amateur achievement in short-wave trans- its pages subject matter of still greater interest mission. than has been found between thé covers of However, the honour of being the first earlier volumes. We believe that at the British amateur to report an exchange of p: esent time the majority of readers are messages with an American falls to Mr. interested particularly in the practical side Frederick L. Hogg, of Highgate. From about of wireless, and we are therefore incl ding 4 o'clock on the morning of the 17th March, special a tides of a practical nature in greater until nea ly 5.3o, Mr. Hogg of 2 SH was proportion than in the past. Mr. Philip R. maintaining touch with the American station Cou sey will describe, in a se. ies of articles, 1 ZZB, and whilst there was naturally con- how to make up standard apparatus for siderable inte.feience, more especially in re- measurements in wireless, and he will ex- cepti n on the other side, it was nevertheless plain the practical application of the instru- possible to exchange information and arrange ments. Mr. F. H. Haynes, who in tee past an appointment for further experiments. has contributed articles under the title of We hope to say more of this success in Experimental Station Design, will write a later issue. www.americanradiohistory.com ` 2 THE WIRELESS WORLD AND RADIO REVIEW APRIL 7, 1923 Experiments with the Neon Tube -I. HOW A NEON LAMP CAN BE MADE TO PRODUCE OSCILLATING CURRENTS. By S. O. PEARSON, B.Sc. URING the past two or three years for further experiment and lead to further a considerable amount of attention applications. D has been focussed on the Neon Tube. In order to carry out such experiments as A great deal of research has been carried out these, it is almost essential to have a know- in England and on the Continent, but unfor- ledge of the chief characteristics of the neon tunately very little has been published up to lamp. It will be seen later that the effective the present time. However, one outcome resistance between the electrodes when the of these researches has been the perfecting lamp is glowing, decreases with increase of of the Neon Lamp as supplied in this country current ; hence a steadying or ballasting by the General Electric Company, Ltd., resistance is connected in series and mounted under the trade name of " Osglim " and these inside the cap of the commercial type of can be purchased quite cheaply for purposes neon lamp. This resistance should be of experiment. removed for purposes of experiment in order A Neon Tube consists essentially of a glass that a voltmeter, condenser or other apparatus bulb enclosing two metal electrodes and filled may be connected directly across the electrodes. with neon gas at reduced pressure, neon being one of the rarer gases. When a suitable difference of potential is applied to the elec- trodes, a discharge takes place through the gas and a luminous glow is formed over the entire surface of the negative electrode or cathode. This glow has a soft velvety appearance, its colour being a yellowish red or orange. No glow is formed on the anode when it is arranged in the bulb in close proximity to the cathode. In the commercial type of discharge lamp neon is used on account of the fact that the voltage necessary to start the discharge is less for neon than for any other gas. One of the greatest difficulties which had to be overcome was the tendency of the glass bulb to become blackened on the inside, this blacken- ing being due to minute particles of the By Courtesy of The General Electric Co., Ltd. cathode which are shot off and deposited on Fig. 1. Forms of Neon Lamps. the glass. This difficulty has been overcome THE VOLT- AMPERE CHARACTERISTIC. by including certain impurities in the gas, If the voltage applied to the electrodes and the electrodes are made of the purest of a neon lamp is gradually increased from iron. These lamps are now supplied for zero, it is found that no current flows and the voltages ranging from 200 to 250, and are lamp does not commence to glow until a voltage primarily intended for purposes of adver- of over 160 is reached. In a particular lamp tisement or decoration, the negative electrodes tested the discharge commenced when the taking the form of letters of the alphabet, pressure had reached 171 volts and the current numerals, etc. Two forms are shown in suddenly increased from zero to nearly 3o Fig. r. milliamperes ; but although the voltage was However, the radio experimenter will be kept constant at 171 when once the discharge interested more from the point of view of the had commenced, the current did not remain possibility of application to radio work, and it at 3o milliamps, but began to fall, rapidly at is intended here to describe one or two dis- first, and then more gradually until after coveries which, it is hoped, may form a basis five minutes or so it became constant at www.americanradiohistory.com APRIL 7, 1923 THE WIRELESS WORLD AND RADIO REVIEW 3 14.7 milliamps. This falling off of current neon tube eminently suitable for use in is partly, if not wholly, accounted for by the conjunction with valves for the automatic rising temperature and pressure of the gas recording of wireless signals. These two in the bulb. It has been shown* that the devices, which are both due to Mr. H. St. G. temperature of the medium surrounding the Anson, are considered in turn below. bulb has a decided effect on the final steady value of the current, this becoming less as THE PRODUCTION OF INTERMITTENT CURRENTS. the temperature is raised. The critical starting Before describing the actual arrangement voltage seems to be quite definite for a given it will be necessary to consider very briefly temperature. what happens when a condenser of capacity INITIAL VALUE C farads is connected in series with a high .,0 resistance R, and a voltage V is suddenly f applied to the ends of the circuit. At the in- 0- 20 stant the voltage is switched on, a current 4 commences to flow through the resistance, J and the condenser begins to acquire a charge. 10 The current has its greatest value at the start when the potential difference across the con- o 140 160 150 200 as a. denser is zero, and dies away the voltage VOLTS across the condenser builds up, until eventually voltage becomes equal Fig. !. when the condenser to V, the current ceases altogether, assuming condenser has perfect In obtaining the characteristic curve shown of course that the insulation. y is the voltage across the in Fig. 2, the final steady values of the current If at any instant, then the voltage were found for increasing values of the voltage, condenser is to (V v), and therefore which was measured by means of an electro- across R equal - equals (V v)/ R ; that is, static voltmeter connected directly across the charging current - is proportional to the difference electrodes.
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