The Wellington Radio Exhibition

Radio Record, Volume II, Issue 53, 19 July 1929, Page 16

The Wellington Radio Exhibition

Exhibits Outside the Trade’ —

ROBABLY. the most active .and enthusiastic body of radio listeners in New Zealand is that section of the listening and transmitting community known as the Association of Amateur ' Transmitters. With the head office’ in Auckland, this strong organisation has branches in the main cities of the country. From head office a journal representative of the whole society is regularly published, while ~ the Canterbury branch publishes its own magazine, "The Canterbury Radio Journal," : ‘-The amateur transmitters of the world form a great brotherhood united by strong bonds. With transmitters ranging in power from a few watts to several kilowatts, these amateurs in all countries are able to hold two-way communication with those on the other side of the globe. Most of the New Zealand amateurs can claim at least .more communication with England and the Continent. Some more fortunate have "worked" the foreign countries on telephony, but as this requires:a fairly expensive plant there are few. to he found amongst the amateurs.’ An amateur aims to develop resource, and a good amateur claims to be able to establish a communication at least over a radius of a few. hundred miles or so with any old wirelessy "junk" and a wire fence. a The amateurs always aim to aid one another and to aid anyone who is interested in wireless with a view to ultimately putting him on the air. Huaving found someone more than passingly interested in radio he is entitled to join the Amateur Transmitters’ "Association, and some particular members . mark him off for particular help. He is guided along lines of study and special slow morse is put over the air to assist him. When he finally takes his examination and qualifies as ‘a transmitter, every assistance is given in the selecting of the components and the setting up of his transmitters, "Ham fests" are held ‘at regular intervals. Amateur transmitters gather ‘ together for a conference, lasting usual-

¢ ’ ly for several days. ‘These are quite a feature with amateur transmitters, Exhibition Activities, T the Wellington Radio Exhibition | these amateur transmitters are having a stall. In it will be exhibited twelve or thirteen active transmitters, the details of which are as follow:-

The transmitter and receiver of 2GA: This is a unique exhibit. ‘Fhe transmitter. and receiver are arranged in a case 12 x 5 x 5 inches, the transmitter itself being of no greater dimensions than 5 inches, each way. Dry cells are carried to operate both receiver and transmitter, and a switching device enables it to be changed over at will This particular receiver has been in constant use and proved itself fully reliable. 2GA is also exhibiting a

portable crystal controlled transmitter with a power of 50 watts. 2GK’s transmitter is of the master oscillator type, with a power amplifier, A Hartley H.C. circuit, taking 18 inches of space, is the exhibit. of 2G0. Another portable receiver will be on show-that of 2BC, a Split Colpitts, which measures 3ft. x 3ft... 2GR has

a Hartley 18 inches long, using a 10watt valve. 2BE has.a-150-watt Hartley 2ft. square and 4ft. high. Within these dimensions is enclosed the whole transmitter arranged in tiers. On the bottom is the power. pack containing the rectifying valve and the _ filter, Above this are the valves and the ‘inductance coils, and so on, each tier representing a-step forward. In no ease is power or signals sent back~to a lower level. The power enters at the bottom and leaves at the top as modulated current ready for the aerial. A ’phone transmitter, with both modulator and oscillator, is the exhibit of. 2AJ: In addition, there are several ‘short-wave receivers, embodying the latest ideas in this class of receiver. The stall will be covered with QSL cards denoting that signals from these transmitters have been heard all over the world. In addition, it is hoped to have a large map with tapes leading from the cards to indicate thelr country of origin, .. . Milestones in Radio History. The "Radio Record" stall at the exhibition will be a departure from the others in that where the trade will be exhibiting the very’ latest that radio science can produce, this stall will be exhibiting apparatus that is long since antiquated, An endeavour will be. made to trace the growth of radio as represented in its. apparatus. . Noteworthy will be a series of cells depicting the methods in which’ electric

power has been obtained, The first exhibit of this series will be the simple voltaic cell of 100 years ago. This was no more than two plates immersed in a solution of dilute sulphuric acida very feeble current could be extract- ' ed, and instruments will be employed _ to show how this feeble current flows , from one plate to another. . The next cell of importance is the Daniels. cell, which for some considerable time was the standard cell for obtaining current electricity. This consists. of a- plate of copper immersed in copper sulphate and a zine plate immersed in a’ dilute sulphurie acid kept from the CuSO #% by a porous pot. A ‘steady current could be taken from such a cell for some considerable. time, the voltage of each being approximately one . volt. These cells were objectionable, in that they were both bulky and comparatively inefficient. However, they served their purpose in the march of electrical science. * Following the Daniels cell, the Leclanche cell which: to-day forms the ‘basis of dry battery power was evolved, This eomprised a central porous pot filled with manganese dioxide surrounding a carbon rod. This. porous: pot was immersed in a weak acid solu: tion in which stood a zine rod. It wag found that a voltage of 1.5 could™be taken off this intermittently, but as soon as a continuous current was taken -@ gas collected round the zine, the. internal resistance rose, and the cell had to be left for. some considerable time to recuperate. However, this' was a distinct advance on anything ‘yet invented. The dry cell is merely an. adaptation of the Leclanche, and. this-is the basis of our dry batteries. Sections of ‘various cells-comprising "A," "B," and "©" batteries will be on view, and. there ‘will be someone to tell the visitor all about them. Following ‘the- Leclanche ‘eell, the accumulator was evolved. This is entirely different from the others, in that electric power has-‘to be put in before it-can be taken out-in other words, , electricity is stored; but with its. form changed from active to inert electric-" ity. An accumulator in a’ dismantled ‘form will be on view, and visitors will be able to see exactly what is. inside that heavy black object that they have laboriously to carry to the chargingy station to be regularly charged. ‘ But electricity derived from the dynamo is tending to replace battery power, and the. latest development of radio science will be represented by a power amplifier obtaining all its power from the 230-volt mains with which our houses are wired. Besides these interesting exhibits of historical. importance, there will be on. view home-constructed models of more than passing interest. Of these, we can but mention a huge eliminator which will deliver half an. ampere of. current at a-yoltage at anything from 1 to 2000 at half ampere. A home-con- ~ structed electro dynamic speaker in dismantled form will be on -view ta visitors, Hxperts from the:"Radio Record" will be in attendance, and will.be ready to discuss problems with. anyone . who may be interested, . ‘ .

& 1 ‘ eompetitions for constructors on behalf HE Amateur Radio Society of Wellington, which is conducting the of the Radio Exhibition .Committee, was founded about six years ago, hefore: broadcasting as we know it to-day, was inaugurated, e Wellington during the infancy of the Radio Society was served intermittently and regularly by low-power broadcast stations maintained partly by voluntary ‘subscriptions from ‘the trade, and listeners.. The programmes comprised gramophone:records lent. by kind enthusiasts, and items by local and occasionally visiting talent. ‘Where assistance is on a purely vol‘untary basis, a service is difficult to mInaintain, and, as’ the operating and. siintenance charges of the broadcast"rag plants were considerable, little wonder that the service was such that broadcast listening by the general publie made very little progress. It is due to those hardy pioneers of broadcasting, however, to mention that they undoubtedly firmly established the cult of broadcast listening in New Zealand. There were "outside" stations in Auckland and Dunedin in those primaeval days, which afforded Wellington listeners a good deal of pleasure by their excellent programmes and transmission. But, again, ‘teeir maintenance was based \partly on voluntary contribu-

tions, and it was abundantly evident that New Zealand, if it wanted to keep abreast of the times, must establish a national scheme of broadcasting supported by compulsory financial contributions by both the listeners and the radio trade. From the outset the Amateur Radio Society of Wellington came under the control of broadeast listeners, though the original idea of the founders was that amateur morse . transmission ‘should take a prominent place in the activities of the sociéty. So strong, however, was the broadcast listening section of the society from its very inception that any moye -towards the carrying-out of amateur morse transmission was néver discussed after the initial meeting of the society. Those who prominently opposed amateur transmission pointed out that the logical trend of radio was towards broadcast listening, and that in. a few years the number of amateur transmitters in New Zealand would constitute only about three per cent. of the number of radio licensees.- That this estimate was fairly accurate is borne out by the official figures of to-day, It was regarded, at the outset, as obvious that the interests of broadcast listeners and amateur transmitters were not the same, and, unfortunately, were, at that time, in conflict owing to a good deal of annoyance caused -broadcast listeners through interfer-

ence by amateur transmitters who were not then employing the. ultra-short-waves now in vogue. * In justice to the anfateur transmitters, it must be explained that broadcast receiving sets were far more difficult to operate during that period, ait a reasonable degree of selectivity was not obtained, either through lack of skill on the part of the listeners, or inherent faults in some of the circuits employed by them. In individual in‘stances there were faults on the other side. , Feeling ran pretty high at times between the broadcast listeners and the iumateyr transmitters, so that any suggestion that the Amateur Radio Society should establish a.morse transmitting station was tabooed. The hatchet, however, has long since been buried. HEN the: Radio Broadcasting Company of New Zealand commenced operations about the end of 1925 it marked the dawn of a new era of broadcasting in this country, .and in less than three years the number of licensed listeners throughout the Dominion rose to over 40,000. With the general progress of radio, vast inprovements have been made in radig ‘receiving circuits and all forms of equipment, and the public of to-day biuve the benefit of the concentration of years of scientific research and experience. The Amateur Radio Society of Wellington has increasingly striven to be of service to the general body of broadcast listeners, as well as its own members, The general meetings have, excepting in few instances, been open to the general public. Per medium of lectures by the most expert radio men of the community, the society has endeavoured to assist the broadcast listener whether~he be a home-constructor or merely one who desires to learn the principles governing radio reception und reproduction. The care and attention of radio equipment, the most desirable type of components to use, and the reason thereof, have also been exhaustively dealt with in these lectures nut regular monthly meetings, generally held now in the Congregational Church Schoolroom, Kent ,Terrace, on the second Tuesday of each month, While not claiming to be the moutbpiece of the general body of broadcast listeners, the’ Wellington Society frequently. acts as a medium in placing before the Broadcasting Company trepresentations corsidered likely to inerease the popularity of the broadcast service. In a number of cases these suggestions have been adopted by the Broadcasting Company, and the friendliest relations exist between the company and thé society, even though their opinions may not always coincide. In keeping with -the policy of the Welli,gton Society, it has consented to conduct the competitions for constructors, and also the essay competition on behalf of the Wellington Radio Exhibition Committee, These competitions are strictly confined to amateurs whether members of the society or not, and it is anticipated that there will; be numerous entries in sall four competitions. In the constructional competitions neatness of york and design will be important factors in determining the prize-winners, The society has obtained the services of a radio technician of outstanding ability to act as judge.