NEW WIRELESS WONDER

Hokitika Guardian, 26 June 1930, Page 2

NEW WIRELESS WONDER

S UCCKSS FITL DEM ONSTR AT lOXS

INFINITE POSSIBILITIES. An invention apparently of enormous importance to enlarge the world communications by wireless and cable lias been made by Or. James Robinson and his apparatus has been demonstrated at his place in London before many of the leading wireless experts with remarkable success (writes Ur R. W Mallows in the “Manchester Guard ian”). Behind this invention of the Sternal" Radiostat method of coimnunieation by both wire and wireless lies an interesting story. Rather more than a year ago it occurred to Or Janus Ifobinson ■‘’onnerly head of the Wireless Research Department of the Royal A’" Force, that a world problem of an extraordinary nature wou’d .shortly arise. The land line, the submarine -able, and the wireless transmitter had nroyided modern limn with means c l ' coinlliuniciltioli uiulrcaln’t. of by hi' "orefnt-hors. but progress Was likely to mine in a matter of a few years at the outside to a full stop. The reason would he this; under cm 'sting systems the mini her of' messages that could he isent and received simultaneously over a wire Vas limited bv practical consideration. He did not believe; that each cable or land-line bcii l " used to the maximum extent possible, hut no lorwn .system could lie shown means of increas'ii" the* mimboi- that could he handed simultaneously. Tn wireless the outlook was even h-rs satisfactory, for the time r l, 'List approaching when so far as could he seen every available wave-length would b* appropriated, and there would ho room for no m'-’-p t'-a”sipitting, stations.

leaders will probably he most fninilhar ‘Mi conditions upon the hand oT wavehumdhs assigned to broadcasting. What *s known as the medium wave.band extends in Enron" from about 200 to 550 metres. This band appears already to lie overcrowded, and since new stations are continually coming into operation it could lie only a matter of time, unless some change were made in reception methods, for jamming in some form to become the rule rather than the exception. A good many years ago it was conceived that a telephonic transmission liv wireless takes place not upon a single wave lengths. The sideband theory holds that above and below the carrier frequency are hand of frequencies produced by the modulation. Experiments appeared to show that lindistorted reception could not be obtain ed unless the receiving .set were so designed that its tuned cireuts were capable of passing a band of frequencies at least nine kilocycles in width. Dr. Robinson decided to approach the problem from a new standpoint. Selectivity is obtainable in tuned circuits only by reducing damping losses, and it, is easy to satisfy oneself that “low loss” and high quality do not go band in hand. But is the reason for this to be found in the cutting out of shlebands in such a circuit? The conclusion to which he came was that quite a different cause was at work. Tn an interview, he claimed that his discoverev would — Considerably reduce interference from electrical apparatus. Solve the oseilation problem: Prevent “wipe out,” and make the reception of distant stations possible under the shadow of Brookman’s Park.

Reduce" interference from “spark” stations and atmospherics. The new receiver embodies the Piezo-electric crystal, which passes only the narrowest hand of frequencies, through what has been described as a “narrow gate.” Dr Robinson also declared that the stenode would enable broadcast stations to be multiplied many tunes, and for any station to be received with perfect clarity to the exclusion of all others. It had been considered in the engineering world that saturationpoint had almost been reached in the ether, he said, this being based on the sideband theory. This state of affairs appeared to put a ban on progress particularly as wireless progress had consistently been to make receivers more and more selective. In fact, one of the main advantages of the valve was that it enabled us to improve selectivity.

“However, as it was considered that we must tune our receivers broadly in order to receive any one station we thus reached the condition that it was not worth while progressing farther along the historic lines of a search after selectivity.

“T have broken right through this barrier, and shown that there is no stoppage* in the way and that future same lines as previously a search after the utmost selectivity. Tims we can now look forward to continual improvement. and such tilings as the "lmiinatioh of atmosnherics and electric disturbances sie-li as 4 those produced by vacuum cleaners and other domestic devices will be made possible.”

Dr Robinson explained: “There is one other aspect of tin* Stenode. which is that the principles an’dv also to telegraphs’, and it is possible to increase shmalling facilities many limes. For instance, on a present-day telegraph line the capacity is such that about 500 words per minute is a very good achievement. The Stenode makes if. possible to deal with 20,000 words per minute quite easily and cheaply, and

in fact this signalling capacity is quite a modest estimate ,of the possibilities.

“There will be a very large application for commercial purposes. 1 visualise the day when, we have enabled wireless to be used foi telephoning America in the same way as we now telephone to a number in the next street. Another aspect is that it wili make telephony and telegraphing very cheap, because there will be so many more channels available. 'We aim at the transmission of hundreds of thousands of words a minute for newspaper purposes.