Another tale from my time on the Orange Harvest test bench at St. Mawgan. Myself and another technician decided as there was not a lot of work to re-jig the test bench. This took a couple of days and once we'd completed it, it was time to test the whole setup to ensure it still worked. So it was all powered up and lo and behold we had a problem. The OH aerial had four "windows" to allow the received signal to enter the system, each window had a co-ox relay immediately after the window to protect the mixer crystal from high power local signals, these were called shutters. We had what appeared to be large signal that seemed to be coming from one window. Having radically altered the system we first suspected it was something we had introduced and spent a few minutes puzzling over what we could have done. Finally, a bit of logic was applied. We closed the shutters and the signal disappeared.
When we turned the aerial the signal didn't change, it still showed the same bearing. Finally we realised that the signal was external. The bay chief had become curious and when we explained what we saw he promptly disappeared. A Few minutes later a bespectacled, somewhat dishevelled Flying Officer rushed into the room. He was the Station Intelligence Officer and we showed him what we had found. He dashed off and left us to puzzle over the situation.
A couple of hours later we were told that a Shackleton T4 on local flying had been diverted to help find the source. They found it! It turned out to be a Russian "Trawler" parked just outside the 12 mile limit on the runway centre line with a height finding radar operating. It promptly left once they realised that they'd been twigged!
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