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Cathode Ray Television

K D Rogers, Popular Wireless July 8, 1933.
    
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Our Cathode Ray Television scheme was such a big step forward in the science of television that it has attracted great attention from radio firms and the press. This article deals with reports that have been published and with letters received from readers.

I suppose it was inevitable that the publication of details of the Cathode Ray Television Viewer should attract a great deal of attention, not only of readers but of the various sections of the lay and technical press.

It was the first thing of its kind ever done, and the detailed description of an easy-to-build non-mechanical television receiving outfit was a step forward in radio that could hardly go unnoticed, or for that matter uncriticised.

Tribute to the Experimenter

The criticism has come from one quarter, and it has been carried out by behind-the-back whisperings of the vaguest character. I have already referred to it in these columns, and a complete answer for the benefit of those who may have heard it (it has not been published!) is being made in a following issue by our radio consultant, Dr J H T Roberts.

Apart from that piece of information I do not intend to devote further space to the subject; it is in itself too trivial a matter, but to the uninitiated, and untechnical mind, such as whence it sprung, it might give rise to completely erroneous presumptions. Hence Dr Roberts article on the subject.

Now let us turn to what has been said openly about our Cathode Ray Television viewer. I have already quoted from Garry Allighan's report of a demonstration of the system in the Evening Standard, but for the sake of those who did not see it, here is a brief excerpt in which he describes it as bringing for the first time 'practical television reception within reach of every amateur experimenter in the country. It is to the amateur experimenter that the country should look for the ultimate triumph of television, as it was the amateur experimenters who were responsible for modern practical radio'.

Informed Opinion

'The secret of good reception of television has now been discovered, but television has yet several years to go before it will have reached the same stage of perfection as radio'.

As can be seen, Garry Allighan, who moves closer in radio circles than most radio critics and press correspondents, shares with us the firm conviction that the future success of television rests with the cathode ray method of reception, and he makes no bones about appraising the demonstration of it that he was given. At this point I must in all fairness bring before the radio curtain Mr T Price of the Ediswan Valve Research Department, who has collaborated with us very closely in our tests, and to whom is due the Special Ediswan T tube used in the viewer. He, and the company he represents, must share the laurels that have been scattered forth.

Here is another report, this time from our technical contemporary, The Wireless World, who describe the system as a 'most promising method of reception', and hail it as ideal for the home-constructor. Follows the main portion of the report:

'Up to the present time most amateur constructors have been deterred from embarking on the reception of television by purely mechanical difficulties. Rotating mirror drums and similar devices, which must be run accurately in step, can hardly be set up in the home workshop'.

Lay and Technical Approval

'The cathode ray system of reception has the advantage that there are absolutely no mechanical moving parts; the images are formed by controlling electrically the movements of a ray directed from the cathode on to the flattened end of the tube which forms a fluorescent screen. Synchronism is similarly ensured by electrical means.'

'Many technical workers consider that the perfected television apparatus of the future will employ a cathode ray tube; indeed, this opinion was expressed by the late Captain Swinton as long ago as 1908 ... It will be good news for British amateurs who are interested in this most promising method of reception to hear that the Ediswan Company have now introduced a special tube for television purposes. Apart from this tube, practically no components other than those used in ordinary radio practice are needed for setting up a practical television receiver, which, as it requires a very small input, may be fed from any ordinary set'.

The Bournemouth Times devoted two long columns to a description of the system, referring their readers to Popular Wireless for further details, and again hailing it as the keystone to perfect television. Here are two typical extracts:

'I have no hesitation in saying that this new television development is not only going to revolutionise the whole question of 'radio pictures' in this country, but will also prove the starting point for all future research in this direction ...'.

Demand for Demonstrations

'I have been able to make a full examination of the apparatus and to see it in operation. Nobody claims it to be perfect, but it is thoroughly practicable and, most important of all, it is working along lines which allow for almost unending development'.

'The picture, though small, is exceptionally clear and the operation is simplicity itself'. (The picture measures 100 × 40 mm - KDR) Since the commencement of our description of the television viewer a large number of members of the radio trade have inquired for further details and for demonstrations, which have been kindly given them by Mr Price, who has rigged up a demonstration outfit at his laboratory in Ponders End.

Members of our contemporaries staffs have been along to see it, and everyone has expressed himself most interested, while the general consensus of opinion tallies with that of the press, whose reports we give above.

Trade Visit

Mr Joseph, Managing Director of Radio Instruments, recently called specially to sec me, to gain further information, and since that date has been given a demonstration at which he was extremely interested.

In fact, so much has the attention of the public and the trade been drawn to cathode ray television reception that both Mr Price and myself have been kept pretty busy for several weeks dealing with inquiries and arranging demonstrations. Even the BBC have asked for a 'look' at Ponders End, though at the time of writing I believe the demonstration date has not been fixed.

And now for a few words to some of our readers who have written in either expressing appreciation, asking queries or offering useful suggestions. They have been so numerous that I cannot possibly reply fully, if at all, to all of them, and those who have asked definite queries I have had to refer to the Query Department.

To the other communications I will reply if I can, but, in any case, will the writers of my many interesting and sometimes long letters please accept my appreciation and thanks for the views and suggestions contained therein.

Special Thanks

Especially, I should like to thank Messrs. G W of Eastbourne, F Dicks of Edmonton, J Glover of St Peter's, Broadstairs, J Smith of Palmers Green, and the many Scottish readers who have given useful information regarding the possibilities of television reception in various parts of the country. I am sorry you are so badly served, Scotland, especially as you are all so keen.

In conclusion, the following letter from a member of the East London College, Department of Electrical Engineering, will be of interest, as it deals with his experiences of AC operated cathode-ray tubes.

'Dear Sir, - I am interested in your articles on Cathode-Ray Television, and I note in the current issue your suggestion that certain sections could be mains-operated, but risk of LF interference is rather large'.

Recent Tube Developments

'I am using an Ediswan tube, together with one of their mains units, and at first had great difficulty with AC ripple, but which I have now completely eliminated. The chief trouble appears to be due to electrostatic charges on the surface of the glass, and I have made tests to show the distribution of these charges on an unshielded tube'.

'The practical point which may be of interest to your readers is that the difficulty is very largely overcome by putting a guard-ring, consisting ofb a band of tin foil about one inch wide, around the neck of the tube at the point where the tube begins to open out, i.e. just ahead of the foremost pair of deflecting plates. The tin foil should be connected to the pair of plates that are common and earthed'.

'I should be glad if you would make use of this note, in the hope that it will help to improve the performance of Messrs. Ediswan's tubes for television purposes, as they have very kindly lent me a tube and mains unit for my experimental work'. Yours faithfully, Leonard P Clifford.

Stop Press

As we go to press I have received news of a further development by Ediswan in connection with the cathode-ray tube - the production of a screen that provides a black and white image. This, of course, is a great advance, and I shall have more to say about it later

We thank the many readers who have written to us in connection with our Cathode-Ray Television Viewer Mr Rogers is here seen dealing with a batch of these letters.

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