Is The Second Greatest Radio Problem Solved?

Radio Record, Volume IV, Issue 18, 14 November 1930, Page 29

Is The Second Greatest Radio Problem Solved?

New Receiver Prom‘ses to Prevent Station Interference

-IUTSTANDING claims are | made for a new British ie- | ceiver, the Stenode Radiostat, | which. promises to solve’ the yx} great radio problems of over- ®& ai crowding channels. It is *} heralded as the greatest single invention in radio since the™introduction of the thermionic valve. From the "Christian Science Monitor" we take the following description :- HE Stenode Radiostat system comprises a number of patents relating to the inventions of Dr. James Robinson, late chief of wireless re‘search to the Royal Air Force, which have. a very important bearing not only upon wireless telegraphy and broadcasting, but also upon cable and land line working and television. Toward the end of last year, a demonstration of a Stenode Radiostat broadeast receiver was given to the trade and technical press, and at a dinner given at the Hyde Park. Hotei, a number of -highly important and even sensational claims were made for the Stenode Radiostat. The actual demonstration given was the reception of Brookmans Park on a_ loudspeaker, while a. powerful local oscillator was made°to produce very bad héterodyne’ interference on a normal receiving set in the same room. When tuned in on .the Stenode Radiostat receiver it was shown that Brookmans Park could be received entirely free from .any heterodyne interference. A disclosure of the actual circuit and apparatus’ used was not given at this time owing to the patent position as many of the important devices used were only provisionally covered. Furthermore, the apparatus then demonstrated was not in a suitable form adequate to demonstrate long distance reception. Critics Dubious. OWING to the, limited nature of the demonstration, a number of criticisms were quite fairly made. Ohe critic, for example, made a comment. on the claims in the following ter ‘: "It would be interesting to know ‘to what degree sensitivity has been sacrificed to obtain this result. "We await further details, especially as to the actual results obtained in practice. We would suggest as a useful test the reception in London of Stuttgart (833 k.c.) while 2LO° (842 k.c.) is. working. In view of the claims made. for the system we feel, however, that we should apologise for suggesting. anything so easy." A demonstration was given showing. for example, the test suggested above, .e., the separation of Stuttgart from London, .and, much more important than’ this, that stations which are ' actually heterodyning one r ‘ther ant proving by the heterodyne note: that the separation is only 1000 or 2000 eveles, can be clearly separated and received in good quality, |

The sensitivity of the apparatus is now such that there was no need to produce the interference locally in order to demonstrate the principle, while it will be’ noticed that the quality of reproduction was of a very ' high order, giving a proper reproduction of all frequencies from the lowest to the highest. . . It is interesting here to consider for a moment the present position: in relation to. broadcast transmissions. . By general consent of wireless authorities throughout the world, radio telephony stations cannot. be placed closer than 9000 or 10,000 cycles, for three reasons: Firstly, it is.claimed that satisfactory reception of all the frequencies which it is desired. to. include in- broadcast reception cannot be effected. unless the receiver responds not only to the carrier ‘wave frequency but to a band of frequencies arnroximately 5000 cycles on each side f the.carrie® wave, Secondly, that if stations are placed closer than this the so-called side band frequencies will heterodyne with-one another, producing interference. Thirdly, that the carrier waves will heterodyne, producing an audible: beat note. The purpose of this demonstration was not to deal with theories but with facts, and it was desired to show that, the reception of the carrier wave alone, or rather the carrier. wave with a very few cycles on either side, was sufficient to. get a proper reception of all the modulations of radio telephony. A Million Dollar Idea. FOLLOWING these remarks, there was little made public for some six months, till in its most recent issue, "Radio News," in an editorial headed "A Million Dollar Idea," says:- ~ As this editorial is being written, engineering representatives of an English inventor, whose new system for radio transmission and reception. may upset and greatly improve our _ present method, are preparing to leave London for New York.. They are bringing models of receivers which they claim will enable us to operate three times the present number of broadcasting sta-~-tions, without interference, on the present broadcast band. These new receivers are neither expensive nor difficult to build. We must admit having been mildly impressed in much the same way when the first newspaper announcements of the Stenode Radiostat appeared about a year ago. The claims made for it were so broad that we took them with a grain of salt. We noted that they were being made in the name of a group of estimable English scientists, and decided that it might be well to investigate, even though the claims ‘made in the newspaper articles could not be reconciled. with current engineering practice. A few years ago, when we organised the International Radio Broadcast tests, we were fortunate in having the hearty co-operation of Mr. Hugh S&S.

Pocock, editor. of the "Wireless World" and "Radio Review," in London. Through our correspondence we came to know him well, and to hold_ his judgment in high regard. We cabled for a report from him. It was not very

encouraging. Nearly six months late? the subject came up at one of our editorial meetings, and we decided upon further. investigation. -The’ reports were extremely interesting. We found that Mr. Percy Harris,

formerly technical editor of Mr. Pocock’s publication, had resigned to become chief engineer of the British Broadcasting Corporation, Ltd. We wrote him and received a much more complete picture of the myriad applications which may be made of what. apparently is the most startling invention of this decade. We invited Mr. Harris and his assvciates to utilise the facilities of "Radio News" laboratory on their contemplated visit to this country, and are happy to announce their acceptance. Within a few weeks we expect to be able to demonstrate some of the simpler applieations of Dr. James Robinson’s extremely interesting invention. Incidentally, many demonstrations have been made before the leading European scientific bodies, and many

governments are now investigating its operation. Among other things, the London "Daily Mail," which publishes in Manchester and in London, simultaneously, is now using the Stenode principle on a wire telegraph line between the two cities, with the result that the communication capacity of the lines has been increased many times. So much has been said, and so much purposely left unsaid about television, that any reference to it usually compels attention. Perhaps it is wel], then, to say that in the opinion of the inventor, the Stenode Radiostat is the key to the broadcast television problem, because it will permit, within the limiting factors which other portions of the television problem

bring about, the establishing of many television broadeast channels without in any way limiting present broadcasting facilities. ‘Not the least interesting is the possible application of the Stenode application to amateur or "ham" activities. If is common knowledge that there is not sufficient room for these ardent investigators in the portions of the frequency spectrum assigned them by international agreement, through our own Department of Commerce. The section now allotted to the amateurs for radio telephone communication is particularly narrow, and radio telephones require a’ wider band for each station than is necessary for radio telegraphy. Without in any way altering international agreements on frequency alloeation the Stenode, it is claimed, will allow the amateurs to increase the number of existing stations and enable them to improve the character of transmission and reception as well. The Stenode applied to telephone and telegraph lines will, by increasing the number of conversations possible over each line, result in tremendous saving in equipment, and a great increase in telephone and telegraph facilities along with great reduction in the cost of these rapidly expanding services. We have called the Stenode a "Mii- lion Dollar Idea." After learning of its multiplicity of applications, we feel sure that our estimate is conservative in the extreme. Perhaps we would be nearer the correct figure if we made it a billion.. In any event, it is with keen gratification that "Radio News" will place all the authorised information by the inventor of the Stenode Radiostat at the disposal of the communications services of the world each month.