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High Vacuum Valves

KD Rogers Popular Wireless, April 22, 1933.
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A new range of British-made Two-Volt valves.

Before me, as I write, are half a dozen slips of paper. On each is the picture of a radio receiving valve, its price, name, list of ratings and characteristic curves. A few words on operation follow and then: The High Vacuum Valve Co., Ltd., 113 - 117, Farringdon Road, London, EC1.

These slips have been taken from six valve cartons, containing the two-volt range of a new British-made valve - the Hivac. On the anode of each valve is stamped the letter H, in the same way as a well-known valve firm stamps its products, while assembly of the electrodes is excellent.

Types Available

What is more, the slips referred to are perfectly truthful, and give accurate average data concerning. the characteristics of the Hivac valves, which, on test, have proved themselves perfectly satisfactory.

Here are the various types available: SG2l0, VS2l0 (variable-μ), H210, D2l0 (special detector), L2l0, and R220. The main characteristics are: Slopes, 1-0, 1.0-075, 1.15, 1.25, 1.2 & 2.0 respectively; while the impedances are 250,000, 110,000, 22,000, 12,000, 8,600, and 3,000 Ω.

As can be seen, these are good, and in practice the valves behave just as one would expect from the figures.

The prices form the most astonishing, part of the whole range, however, for the SG valve costs but 10/6, variable-mu 10/6, while H, D, L, and P types are only 4/6 5/6, 4/6, 5/6 respectively.

At such prices I imagine that there will be a ready sale for Hivac valves, in as much as they are really well made, and are not just low-priced.

The Matter of Evacuation

It takes some enterprise nowadays to enter the lists of the valve manufacturers, for though it may appear that the turning out of vacuum tubes is a comparatively simple matter, it is by no means easy to ensure that every sample (less an inevitable low percentage of 'chuck-outs') shall be up to standard in characteristics, and also contain a high vacuum.

The matter of evacuation of valves is a most important one, inter wrapped with the choice of electrode metal and the process of gettering and electrode heating, for the final success of the valves depends upon all those things being done properly, and done consistently well.

Hivac valves live up to their name as far as the samples I have received, and I think that in all fairness to the makers I ought to say that if all their specimens are as good as those I have. had, it will mean another make of valves for Popular Wireless to use in the research and test departments, and another addition to our published lists of recommended valves.

Primarily, I am not concerned with matters of price; for either a valve works well or it fails in its purpose. The Hivac valve (made in London, by the way) is primarily a good valve; that it is remarkably cheap is so much extra ballast.

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