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A Great New Valve Development

PW Research Department Popular Wireless May 27, 1933.
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Two weeks ago this journal published exclusive details of the latest thermionic tube development - the Catkin valve - and gave details for building the first Catkin set. Below we give further details of this remarkable development, which inaugurates an all-metal-valve era of the greatest importance to set builders.

The human appendix and the familiar glass-enclosed valve would appear at first sight to have about as much in common as chalk and cheese. Yet it is said - with what degree of authenticity we do not know - that it was from thoughts such as these that the inspiration for the new Marconi and Osram all metal valves first arose.

Superficially, it sounds a tall story, and yet it isn't really so difficult to trace out the connection.

Why are we furnished with a purpose-less appendage which may cause untold anguish even to the extent of endangering life? If honesty is the best policy the only reliable answer to that is that nobody definitely knows.

The most we can do is to hazard a guess that in the process of evolution the appendix just happens to be one of those gloomy relics of an age that we cultured people prefer to forget; at least, we prefer to forget it if the answer is to be found in the shade of medical opinion which associates the appendix with a tail!

Why Glass Containers?

And why, up to now, has it been customary to make valves with a glass container? Again, the only answer is that it just happened in the process of evolution.

From the early discovery that an electronic stream could be obtained when certain electrodes were placed in a vacuum, there sprung to life an apparent similarity in the manufacturing processes involved between the then old-established electric lamp and the new-born baby - the wireless valve. Both required a vacuum, and at the time when the valve was first invented, the electric lamp had been in existence long enough to prove that glass was a satisfactory material from which to make the envelope.

Valves Were Likely to Break

The unbreakable receiving valve that is being examined is descendant of the enormous transmitting valve, also shown here, of the Marconi CAT water-cooled type, as used by the BBC The big CAT valve is nearly five feet in height, and needs about 1,500 horse-power for its operation. See also CAT9

It was from these early beginnings that the structure of a wireless valve as we have known it for so many years took root. Years of scientific progress and ceaseless research have made the modern valve at very different thing from its prototype of the old bright-emitter days. Efficiency economy and even electrode fragility - all have been the subject of intense research and yet in the fundamental respect the association with the electric-lamp industry has never been severed.

If you had dropped a valve in 1922 the chances are that it would have broken; if you had dropped a valve in 1932 - ten years later - you would still have been lucky to have picked up anything but pieces.

So designers thought about the human appendix; they thought about the glass-enclosed valve, and now, again in the process of evolution a valve has emerged which you can drop with the certain knowledge that you cannot break it!

Opens Up a New Era

While it is true that this remarkable development opens up a new era of unlimited potentialities in the technique of valve construction; one has necessarily to pause in the wave of general enthusiasm to point out that it does not automatically render glass-enclosed valves obsolete.

Let us remember that whatever the potentialities of this new method of construction, all-metal valves are still in their infancy, and that consequence it will be many years before the glass-enclosed valve is entirely replaced.

All the same, one must give credit where credit is due, in this instance to the Research Departments of both Marconi and Osram. Truly, it is a remarkable development, and one that we have cause to welcome with unstinting enthusiasm.

Better Radio Comes First

The PW motto is couched in the future tense. Convention means nothing to us if by a radical departure from standard practice the way is opened up to better radio. We had the pleasure of giving readers the very first news of these new valves, and we shall continue to follow with great interest the progress that is made simply because the prospect of better radio in this case is far from being just a conjecture.

It seems unnecessary again to expound the constructional merits of the new Catkin valves, since the subject was comprehensively covered in our issue dated May,13th. The only information to be added to that original description is that in the pentode finally standardised for production, the protective outer cover, which, in the case of the SG and detector types, can act as an efficient electrostatic screen, has been dispensed with.

A Test By Post

This is the Osram Catkin valve which travelled by post from London to Aberdeen and back exactly as shown without any protective covering! On arrival it was plugged straight into a test receiver, where it behaved perfectly, there being no trace whatever of internal damage in transit, although the valve had received a buffeting sufficient to bend one of the pins.

But where it is possible for us to amplify our original details is in respect of the claims that are made for these new valves - claims which, by virtue of the fact that they emanate from two firms of the highest possible standing, can be accepted without reserve.

The paramount claim is that the valves are phenomenally robust. The claim is authentic, and, moreover, we took steps to prove it. A Catkin valve devoid of any protective covering whatsoever was despatched by post to Aberdeen, from whence it was returned - again by post - to us. It functioned as perfectly after its post-office handling as it did before it left our hands! Short of a steam-roller, we could think of no more conclusive test.

Uniformity of Production

Then again, it is the aim of the manufacturers that the vastly improved mechanical principles of construction will lead to more uniform characteristics between valves of similar types. A careful examination of a dissected valve leaves no room for doubt in this respect, and it is true to say that greater consistency among valves will ensure even greater consistency in set performance.

Two further claims that are advanced by the designers are: (1) complete freedom from microphonic troubles; and (2) smaller size, the importance of each of which will readily be appreciated.

It has long been known that freedom from the annoying fault known as microphony is entirely a matter of ensuring perfect electrode rigidity. The fact that the phenomenon is completely absent with this new method of valve construction is adequate proof of the soundness of the new principles involved.

As regards size, the general tendencies in set design are all towards compactness, and the achieving of smaller overall dimensions. Here again the advantages of the Catkin constructional principles will be evident, especially in sets of the small console types, where size is a specially important consideration. And the further point that the valves are virtually unbreakable - is also particularly advantageous in relation to mains trans-portables.

Undoubtedly, the advent of Catkin valves is a development of the highest importance, and there is no telling at this stage to where it will ultimately lead. For the time being, all-metal construction is confined to Marconi and Osram valves of the AC type, but as and when further developments are made readers may rest assured that the publication of details and practical designs will cut still another notch in PW's Totem of firsts.b Meanwhile, our 'hounds' are straining at their leashes!

The constructional features of the Marconi SG Catkin valve are clearly shown in this picture, where the anode and screen have been cut away to expose the interior. See also Catkin Valves & The metal valve.
A non-metallised Osram Catkin, the MH4.
An MS4B, which, in appearance, is exactly similar to the VMS4.
This is the first time that PW has reproduced a picture of a tube of tooth-paste! But it certainly conveys a vivid idea of the size of the representative Catkin valve placed beside it.
The non-metallised version of the Osram MPT4, for use on AC mains.

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