大象传媒

The purpose of the raid was to capture German anti-aircraft radar equipment in order to find out the German radar capability. Their latest technology was a device called 鈥淲urzburg鈥�. Although the raid was a great success overall, there was one big problem. It was not made clear to the people on the raid that the valves in the Wurzburg needed to be brought home intact. It was in fact more important for engineers to know the characteristics of the German valves than it was to know the circuitry they operated in. By knowing how the valves behaved in a test circuit, they could work out the other circuit details.

The equipment was brought back, but in the rush and emergency, no care was taken over the valves, which the non-technical raiders thought were just ordinary things like the ones in their wireless sets at home. Fragile - break one, go to the shop, buy another. Back in England work was immediately started, to reconstruct a working unit from the battered hardware. The valves though, had all been smashed.

The endeavour could have ended there but the remains of the valves were sent to the STC valve factory, now relocated in a rural area, away from the bombing. They were passed to Chris Foulkes a valve design engineer,specialising in radar valves, to see if he could deduce anything about them from how they appeared to have been constructed.

Luckily the bases, which were thick glass, had survived and the internal electrodes were more or less intact, although bent. Chris realised that the electrodes could be repaired and he could work out how to realign them. There was a major problem however, because the valves had been made to metric measurements. Chris knew that if he rebuilt the valves, they could be made to work again if he welded fresh glass envelopes onto the bases and drew a high vacuum inside. They had all the necessary equipment, but no suitable size of glass tube could be obtained as all of our valves were made using imperial measurements. Once again, the project seemed thwarted.

On his way home from work, Chris walked past a houseware shop in the town, Doney & Cooke and happened to glance in the window. Wartime shortages meant that they did not have much on display but it happened that they had just obtained a delivery of small Pyrex cooking basins. Pyrex cookware was horribly expensive at that time but as he looked, he realised that they were a size and shape that looked ideal for use as envelopes for use on the German valves. Valve glass was a special type with special thermal characteristics. Pyrex was ideal!

He went in and bought the entire stock, which amounted to 6 basins. Back in the factory it turned out that the basins were an exact fit on the valve bases, with enough room for the electrodes. They were welded onto the rebuilt bases and the air was sucked out. On test the valves worked and gave a clear indication of German radar capability. They were sent back to the team rebuilding the Wurzburg and as a result, it was made to work.

For public consumption, the Bruneval raid was reported as a complete success even before the valve problem was tackled. What could so easily have been an heroic flop became at last an heroic success.

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