Military Marked Radio Valve

World War Two saw the meteoric rise of electronics in warfare. From radars to radios, electronics were the new wonder weapon and all sides invested time and money in perfecting the systems. This development was largely due to the vacuum tube, or radio valve in British parlance. This was a device, invented in 1904, that passed electrical current from one electrode to another in a vacuum and allowed far more sophisticated electronics to be developed. It was not until the 1920s and 1930s that the cost of manufacturing valves dropped enough that the technology became widely exploited and the British military were rapid adopters of the new technology. Like everything else, British military radio valves were clearly marked as such.

I have not yet been able to identify where this valve is from, but it is typical of many in use during World War Two:imageThe valve is made of glass, silvered and painted black, with a large plastic socket on its base to allow it to be plugged into whatever electronic device it was designed for:imageA /|\ mark indicates its British Army ownership and a stores code is also printed on the outside of ‘ZF8B’:imageA metal spike is attached to the top of the valve, although I am unsure what its purpose would have been:imageChris Foulkes was a developer of military valves in World War Two, this is his story:

At the outbreak of war an electronics company, STC Ltd had a factory in Woolwich. There they made valves, not just for domestic radios but also specialist types for radio transmitters and the newly invented radar. Chris Foulkes was a young design engineer in the development labs. Both Britain and Germany recognised the potential strategic advantage offered by radar and were in a race to develop better systems. The Woolwich factory became a priority-bombing target, mainly because it made valves, without which radio equipment could not work. The Germans probably did not know how far advanced we were with radar although they did have spies out, one of whom was suspected but not caught before absconding. The War Department arranged for the whole factory, all equipment and personnel to be relocated to rural Somerset.

In Lufwaffe raids the bombers had formidable protection from night fighters and there was an urgent need to find a way of giving our defending fighters a better chance against them. Britain was ahead in the radar race and the idea was conceived to miniaturise radar sets to be small and robust enough to be carried on our own night fighters. A downward-looking radar system called “H2S” was already in use in bombers, which gave some rough view of the ground through cloud cover. The need was for forward-looking radar with the detailed resolution to pick out a fighter aircraft and distinguish it from a bomber, with a display that the pilot could use for guidance towards his target and aim. The equipment hardware was made by EMI to use special valves developed by STC: small, tough, with suitable power and able to operate reliably at the necessary frequency. The design fell to Chris and the engineers in the Development Lab.

When the time came for testing, a prototype set was fitted into a Beaufighter and flight tested by John Cunningham. Already an established fighter ace, he had also been a part-time test pilot for DeHavilland before the war. After initial testing, when the DeHavilland Mosquito became available it was found to be a natural test-bed for all manner of purposes and Cunningham was the natural choice to fly it for further radar development.

His mounting successes against night fighters were announced in BBC news broadcasts and celebrated as a booster for public morale. It was important to avoid Germany guessing that Britain had developed viable airborne radar. A cover story was put about, that Cunningham’s success came because he ate a lot of carrots thus improving his night vision. The nickname “Cat’s-eye” was created for him, suggesting that he could see in the dark, like a cat. Testing continued until the system was well enough developed and was put into major production for supply to all fighters engaged in night flying.

At the same time as airborne radar was being developed, other systems were developed, to improve ground-to-air radar and to put radar on ships. When all the radar valve designing had been done, Chris designed valves for “submerged repeaters”, which were amplifiers inserted every few miles along the transatlantic telephone cable to America, to improve signal quality. These valves had to have very long lives, as dredging up the cable to repair a repeater in mid-atlantic was very complex and expensive. Many of these original valves were still operating in the late 1960s, when the repeaters were changed over to transistorised systems.


  1. Is it possible these were manufactured in Romania? I have seen that symbol – a triangle with an arrow center – on several Romanian rifles I have owned.

  2. The “top cap” is another terminal, when more complex valves required more connections than the standard base could provide.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.