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M.J.B. Scanlan

 

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Employment

Early Centimetric Ground Radars - A Personal Reminiscence

A QO party generally consisted of two or three men, and its purpose was sufficiently explained by its title. Since there was no stand-by set, the daily maintenance period of an hour was far too short for any deep investigations: the mechanic would go through the tuning procedure and do a few routine checks, taking care not to disturb anything, if possible. Allowing for one or two trips up the tower, an hour seemed an impossibly short time for even routine maintenance: any over-run of the allotted time called forth protests from the plotting room, and possibly a complaint to Wing HQ. The QO party was allowed three or four days, working from 0900-1800 hours. Even then, a QO party which had indulged in any major dismantling in an endeavour to solve a long outstanding problem would take care to begin re-assembly by, say, 1400 or 1500 hours. Every station needed to be at its best during the hours of darkness, when, even if there were no E-boats, the routine navigation of convoys was more difficult and dangerous.

When the Bempton QO was finished, Wing HQ rang up to say that they wanted Mr. Walker back for another job - would I take the party on for QOs at Ravenscar and Saltburn, which were Type 271 stations, 30 and 50km to the north, respectively. I protested that I had never yet seen a Type 271 station, let alone been instructed about it: my companions were only a little more experienced. My protests were over-ruled: 'it's a simple little set', they said, 'you'll soon find your way around it'. This time, at least, Wing HQ were quite wrong.

Type 271 was one of the first, if not the first operational centimetric radar in the UK. It was a naval design, and the prototype had been fitted in HMS Orchis in March 1941(10): twelve more sets were hand-built in Admiralty Signal School Workshops by the end of June, and 52 more in industry by the end of 1941. 350 sets were then ordered (fig. 8 - arrowed, on left hand side of photograph, Ed.).

As adapted for use on land, the Type 271 was fitted into a cabin, perhaps 4m by 2m, and mounted on a turntable. Two 2m dishes were mounted externally on a cabin wall, one to transmit, the other to receive. The display was an A-scope, mounted on a bench in the cabin, with most of the radar mounted on the floor below the bench. The operator sat at the bench to observe the A-scope and traversed the whole cabin manually, using a hand-wheel geared to the turntable: thus he could read off the range and bearing of any target. There was no tower, and the set was of low power but, because it was mounted on high cliffs, the range was adequate for routine convoy watching: presumably F-boats were not expected so far north.

The Type 271 radar may have looked simple as a block diagram on paper, but it was of poor design mechanically and fiendishly difficult to work on. All the RF circuits were in coaxial line (that is, there was no waveguide). In one place, as I remember, two coaxial lines came together in a T-junction, the inner conductors, about 3mm in diameter, being of copper or very soft brass. The end of one conductor was threaded, and screwed into the other: when the threads became slack, as they inevitably did in time, the only solution we could devise was to solder both threads, hoping that the joint would hold tight at least temporarily. No doubt the sensible thing would have been to have telephoned Wing HQ to ask advice, or to seek a spare part. Already, it seems, I was imbued with the QO ethos - don't bother Wing with such a small problem, go ahead and do it yourself. Many more flagrant examples of this philosophy occurred later: I can only assume that QO parties (or at least my QO party) became imbued with hubris, in the dictionary sense of arrogance which invites disaster'. The disaster that followed our Type 271 endeavours look the formidable form of W/Cdr Scott-Taggart, who followed us up the coast receiving the complaints of the station personnel and writing his own which were fairly scathing even in the attenuated form in which they filtered back tome. Fortunately, we had taken care to leave all the paper-work in impeccable order, a strong point in our favour in the W/Cdr's view.

The other problem with the cabin-mounted Type 271 was that all the tuning adjustments were under the bench, while the display was on it. The tuning procedure was therefore to turn the set onto a PE, then sit on the floor to make adjustments blindly whilst craning the neck to watch the display. This was not conducive of optimum tuning, and was positively destructive of good temper and bodily comfort.

We were therefore heartily glad to have finished, at least for the moment, with Type 271. I never saw these two stations again (they were the last in 73 Wing, and were replaced by a high-power Type 277 at Goldsborough).


 

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Constructed by Dick Barrett

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ęCopyright 2000 - 2002 Dick Barrett

The right of Dick Barrett to be identified as author of this work has been asserted by him in accordance with the Copyright, Designs and Patents Act 1988.