Wireless World

Evening Post, Volume CVI, Issue 36, 11 August 1923, Page 19

Wireless World

The notes in this column will give items of interest regarding wireless developments in New Zealand and elsewhere, and items calculated to be helpful to amateurs, paxticularlv beginners. Questions are invited.'.and tho replies t will be published when, they are likely to be of general interest.

New Zealand radio amateurs are fortunate in being practically free from encumbrances in the way of harassing regulations, and their lot is in marked contrast with that of their confreres in Great Britain. Here, for example, there is no restriction on the class of receiving apparatus that may be used, so long as it does not radiate energy so as to be a public nuisance. There is no limit to the size of aerial that may be used. British amateurs are limited (as New Zealanders were at first) to 100 feet of aerial (including the down-lead). With regard to re-radiation, the British amateur is forbidden to commit anything of the kind on the wave-lengths used for broadcasting, though he seems to be at liberty to break out on other wave-lengths. An important effect of this rule is. of course, to modify the use of reaction.' and a very frequent method is to apply a tuned anode circuit to tho first valve and obtain regeneration by coupling a reaction coil to this circuit. The same rule has, of course, the effect of setting experimenters to work to discover methods of amplification that will give fully satisfactory results without regeneration. But the most important difference between Britain and New Zealand arises from the method of financing the broadcasting service. Thiß has been done at Home by establishing the British Broadcasting Company, in which shares are held by the manufacturers of instruments and parts. All such products are branded "8.8.C.," and a substantial royalty is charged upon them and goes towards the cost of the broadcasting service. In order that the royalties shall be available, "broadcasting licenses," enabling amateiirs to install apparatus to listen-in, are issued with the condition that all the apparatus used must bear the 8.8.C. braad. Those who wish for more freedom in making Up sets than the purchase of bought parts will permit can obtain "experimenters' licenses." They are supposed not to listen td the broadcasting; but it is. of course, a polite fiction that they observe the rule. On the other hand, the experimenters' license's are granted only to those who have some technical knowledge and can claim that they are genuinely interested in the experimental and research side of the hobby. Naturally, trouble has arisen ove* people who decline to fall in with either set of requirements It is so easy and cheap to construct a simple wireless set that a great number—estimated by the London "Times" at 200,000 —of unlicensed sets are in use. Their owners are not uncommonly labelled "pirates." The whole position at Home has been rather chaotic, and made rather worse by the fact that the material broadcasted is not up to the standard which the listeners think should be maintained in view of the fact that they are paying substantially through a high protective tariff-in favour of the 8.8.C. On the other hand, the Broadcasting Company js handicapped by the fact that theatrical and other entertainment authorities decline to permit their entertainments to be broadcasted, and the copyTight law is also invoked. Wednesday's cable news from London brought a- brief report of the recommendations made by the committee on broadcasting. The committee proposed what seemed! the only reasonable step in the circumstances —a new form of license for those who make their own sets at home or use materials not branded by the 8.8.0. Those who have studied the subject must generally have come to the conclusion that the 8.8.C. "monopoly," as it is often called, is far from an unmixed blessing. •,.

Up to the present in New Zealand none of the special difficulties experienced at Home have come seriously forward, and there is no sign o£ any incorporated broadcasting concern, co-operative or otherwise, securing a monopoly of the service. Within the limits of the regulations as to overlapping oj territory and times, the ether is free for responsible and authorised transmitters; and now those who have good receiving sets can listen to a'considerable number of broadcast programmes, sent out from various places, and all run independently. In Wellington one company is already broadcasting enjoyable concerts twice a week; another is rapidly completing its equipment, which vail be of an elaborate type; and a third ig in process of installing its plant. These three will fill the week. It is an interesting question whether there is room for all of them, considering that, apart from private subsidies, their finance at present is on the same basis as the advertising account' of any ordinary business. Broadcasting with a high-power set is not cheap, and it can become very expensive if talent has to be naid for. The subject is a very interesting one, and its development will be watched with great interest by others as well as radio enthusiasts. Variometer tuning for the aerial cir cuit is deservedly popular, but it presents some difficulty in the matter of coupling to a secondary circuit This can very easily be got over by using capacity coupluig, which is very little heard of nowadays. The method is to fix tha secondary coil in any convenient position, preferably well away , from the variometer so as to avoid i nduc tive eftect, and to connect one end of ths coil to the earth side of the aerial vario meter. The other ends of- the S ?%Ea se«ondarv .Ending ar e con . nected through a condenser, which may be either continuously variable if such T ™f ral acnt' W" available, O r a «ub divided fixed condenser with a fan switch. The smaller the capacity thl looser the coupling. Such a '^ook v*" used on a crystal set eight miles ou? P nf town enaUed the 15-watt concert tr mission from Wellington to b e lark" heard while VLW was going full ht t its noisy Morse being S^^ I^Vc^nTt^ Sti the operation of a receiver de Den d« , the voltage of the current?n the C lous circuits, at all events ffl, i **£ degree of amplification is reached it point „ of special importance in «£ aerial circu,t. An aerial should be tuned as f ar as possible by mean, nf indu c t ance coils, and as liUle as pos sible by leans of condensers, esPec £n v m parallel; and the detector connec tions, if made direct to the aerial rir cuit, 3 hould embrace a ll the indu c t a nce" In a, secondary circuit the condenser should not be of more than .005 mfd as a rule. The smaller the maximum capacity of the condenser is, the easier it is to secure fine tuning.

An English radio magazine illustrates a very simple way of making a grid condenser. It is to wrap a strip of mica round a short piece of brass rod and wind over the mica some bare copper wire to form the second "plate." I'ho w ; re can be held together with a line of soldei. Clips will servo to hold the rod and provide oi !o connection, and tlio end of the wire forn» tha other tw Oiinal.