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Jetex Jim
5th Mar 2008, 04:15
From Sir Arthur C. Clark:
Flying Officer Alan Bishop found it singularly peaceful on this tiny metal platform a hundred feet above the North Sea. The fact that Adolf Hitler was undoubtedly preparing some sort of mischief over there on the Continent, and that it was his duty to watch out for it, seemed quite irrelevant on such a warm autumn afternoon. Nothing moved in the whole expanse of sea and sky; even the big concave dish of the radar scanner had ceased its restless searching and was staring straight toward Holland. If it did start to spin, Alan would have to move smartly; it was not very practical to share the platform with a whirling ten-foot saucer standing on its rim.

Below him, the rest of the station appeared equally relaxed. But this, Alan knew, was an illusion. In the wooden hut at the base of the tower, Sergeant Campbell was attacking a defective wave monitor with liberal doses of solder and profanity. Over there inside that mysterious barbed-wire enclosure, Flight Lieutenant Hicks, Royal New Zealand Air Force, was assembling his Gee installation -- whatever that might be. F/O Bishop resented the existence of any radar device that was secret to him, but all his attempts to winkle information out of Hicks had been wholly unsuccessful. At least, he consoled himself, by the look of the antenna arrays it was only old-fashioned meter-wave-length stuff, so it couldn't be very interesting.

There were probably fifty people hard at work within a hundred yards of him, but the only signs of life were the bored Service Policeman on duty at the main gate and a Woman's Auxiliary Air Force operator doing some voluntary gardening on the skimpy flower bed around the Orderly Room. At least, Alan assumed it was voluntary; the WAAF Commanding Officer had not, as far as he knew, started doling out horticultural exercises to criminous airwomen.

The parabolic bowl looming above him gave a premonitory creak and twisted toward the south, as if tired of staring for so long in one direction. There was no danger that it would start spinning at full speed -- Sergeant Campbell knew that he was up here -- but Alan thought he had better move.

The big dish was aimed straight at him, and he was sitting in a radio beam of a frequency and strength no one would have dreamed possible only a few years ago. It might be imagination, but he felt that he was already starting to cook.

Half a million watts were squirting silently, invisibly toward Holland, focused into a narrow beam by the big radio searchlight. Not a billionth of that energy was coming back, reflected from whatever obstacles it had encountered before it skimmed clear of the horizon and headed out into space. Yet that feeble echo was enough to betray the presence of any ships or low-flying aircraft within a hundred miles of the coast, and to pinpoint them accurately on the cathode-ray screen in the receiver hut.

There were times, however, when old-fashioned vision was better than radar, and this was such a moment. A mere half mile away was an approaching target of much more interest than Nazi torpedo boats or low-level bombers. As soon as Alan spotted the brown van weaving along the narrow lane, he started to descend the tower with reckless speed.

Despite his early warning, the news was all over the station before he reached ground level. By the time he sauntered through the main gate (it was, of course, undignified for officers to run) the queue for the NAAFI van was so long that it seemed incredible that the station could still be fully operational. If Hitler only knew, thought Alan, he could sabotage the entire radar chain by organizing a simultaneous onslaught of NAAFI vans loaded with off-ration chocolates and cigarettes.


This book, Glide Path, although fiction, is based closely on Clarke's wartime experiences working on Radar - largely GCA

You can download the whole thing from Fictionwise

chevvron
5th Mar 2008, 07:30
It's a very interesting book which as you say, is semi-biographical in the ACC actually was a radar technician and was involved in the development of an early type of PAR using 'A' scopes. His description of the tracking techniques ie 3 radar displays (range, azimuth, elevation) helps you 'picture' the way it was done in those early days, where nowadays the 'tracking' is done for you by a processor.

old,not bold
7th Mar 2008, 15:30
At a vintage glider rally a few years ago I saw a single-seat glider, in a camouflage paint scheme, that was evidently designed and used for either testing radar or calibrating it, or both, on the East Coast of England and over the North Sea.

It's lack of any radio-reflective material whatsoever was its principal feature, but for the life of me I can't remember how or why it was then used with radar!

Is it off-thread to ask if anyone can enlighten me/us? It's about WWII radar, sort of.

Fitter2
7th Mar 2008, 17:31
It's described in Philip Wills' book 'On Being a Bird', He was the pilot. I think it was his Minimoa.

They removed virtually all the metal, including control cables.

I'll look it up when I get home, and report more.

wz662
7th Mar 2008, 17:39
The glider was (is) a Slingsby Kite. It was towed by an AVRO 504 from the cliff tops at Worth Matravers near Swanage Dorset.
In Philip Wills' book he describes the radar operators watching the blips of a German fighter and the glider / tug combo merge, and he wonders if the German would have admitted to seeing the combo miles out to sea. :\

Jetex Jim
7th Mar 2008, 22:17
It's lack of any radio-reflective material whatsoever was its principal feature, but for the life of me I can't remember how or why it was then used with radar!


Wiki says to test if Radar could give warning of an invasion, the type of glider born troops that were eventually used on D Day.

If Radar could have picked up a Slingsby Kite towed by a Avro 504, it would have had to have been working pretty well, I fancy.

I wonder how well a Tornado F3 radar would do against such a target?

henry crun
8th Mar 2008, 01:43
Does any one know what wavelength the 1939 radar used ?

Jetex Jim
8th Mar 2008, 05:17
Quickly looking at the link below
http://www.radarpages.co.uk/mob/chl/chl1.htm

And comparing the pictures there with the ACC desrcription, in that extract, I would say he speaks of

Radar Type 2 (CHL)
Frequency
200 MHz
Tx peak power
150 Kw
Tx pulse length
3 us
PRF
400 pps


1.5 metres

Some of its predecessors radars had wavelengths as long as 20 metres.

henry crun
8th Mar 2008, 05:49
Thanks JJ, I was obviously not asking Google the right questions.

chevvron
8th Mar 2008, 14:53
The CHL suffix stands for 'Chain Home Low' meaning it was for lower altitudes; other Chain Home radars had different characterisitics.

Jetex Jim
9th Mar 2008, 00:26
Hear Sir Bernard Lovell on BBC listen again


1. The Boffins

The first programme is about the evolution of a lab which started during WW2 and which has gone on to become a 7000 strong R&D business, one of Europe's biggest. In its first incarnation the Telecommunications Research Establishment (TRE) developed radar during WW2 and went on to lay the foundations for the information age. The story of TRE is the story of the scientists who helped save Britain from ruinous bombing and invasion and went on to invent computers and air traffic control, modern meteorology, liquid crystal display and the microwave oven. We talk to scientists who remember those including Sir Bernard Lovell.


http://www.bbc.co.uk/radio4/science/rams/futurelabs1.ram

Jetex Jim
9th Mar 2008, 01:02
It's nice to see that Sir Bernard aged 94, and Sir Arthur aged 90 are still going strong.

Googling around these names brought up this 1960's era coupe that Sir Bernard had a hand in.


Earlier, the Russians had gone out of their way to tell the operators of Britain's giant 250-ft. Jodrell Bank radio telescope the precise frequency of Luna 9's transmissions. Forewarned, the British astronomers easily picked up and recorded the spacecraft's signals. Noting that they were suspiciously similar to ordinary wirephoto transmissions, the men at Jodrell Bank fed them into an ordinary facsimile machine hurriedly borrowed from London's Daily Express. The machine converted the signals into a light beam that varied in intensity as it mowed back and forth across photosensitive paper, producing lines of light and dark dots. The results, said Jodrell Bank Director Sir Bernard Lovell, were "the most sensational pictures we have ever received."


If I recall correctly, much to the annoyance of the Soviets, the Express got the pictures to the front page before they were officially released by TASS.