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The TestSignal Corps World War Two August 1, 1951 by Thompson, G. R., D. R. Harris,
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John Marchetti at Camp Evans building 20 - January 1999 |
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| Thinking
in terms of defense had set the tone of American radar efforts early in
1942. Fear for the west coast and for the Panama Canal had led the
military to demand long range detectors and GCI radars, even the fixed
long wave gear of the early British CH and CHL/GCI sets. But as 1942
wore on, concern over passive air defense of the United States coast and
possessions gave way to thinking in terms of Allied offen-
37 Guerlac, Radar, pp. 637 39 (Sec C, Ch. VII, pp. 34 36). Incidentally, it was the SCR's 582 and 615 in the Canal Zone which were first used extensively to detect distant storm clouds and so opened up the possibility of weather forecasting by radar aid. Ibid., pp. 612 13 (Sec C, Ch. VII, pp. 10 11). |
| sives. A fresh
reappraisal found long range detectors necessary at only a few places,
most notably, in Panama. In general the SCR 270 or 271 continued to prove
good enough. Even Saville had acknowledged that the 270 was good
in isolated uses, as on an island, for aircraft detection.
But Watson Watt's belief that such longwave radars alone could attain great ranges was soon disproved by the new microwave ground sets. And the Air Forces' original stress upon mobility, which had led to the first American aircraft detector, the mobile SCR 270, received renewed emphasis in 1942 as military men planned to invade hostile shores. Contemplating attack upon distant beaches where air raids could sow vast harm among congested landing areas, the airmen gave thought to a set which might be taken onto a beachhead in pieces, carried by a few men who could assemble the radar in an hour or two. Its power and range, of course, would be limited but would suffice. The AAF, with its predilection for British long wave sets, turned to them once again, to the British LW, or lightweight warning radar which the Signal Corps copied as the SCR 602, in time for use in North Africa. Early in 1942 Saville had set forth the airmen's requirement for an "equipment similar to the British light mobile or portable early warning set." But this LW radar prototype was not yet in production. Maj. Gen. James E. Chaney had cabled from England that the British would send two sets to the United States as soon as they became available.' In February 1942 Gen 58 Memo, Norman Abbott, Assoc Radar Engr, for O/C Radar Div, 12 Feb 42, sub: Meeting to discuss American GCI equip. SigC 413.44 British Ground Control GCI (RB 2330). |
eral Olmstead asked for information
about this British "light mobile and portable aircraft warning RDF set."
Two months later he had gotten nothing, whereupon he hats asked the Chief
of Staff to make another petition. But even as he asked, the blue,
prints were at last on their way, followed late in June by one of the first
British prototypes. On 25 June General Eisenhower in London notified
Washington that Lt. W. W. Debenham, a Signal Corps officer who had been
working with British radars, was that night leaving Prestwick, Scotland,
the English terminus of the transatlantic air ferry. With him he
had 1,000 pounds of lightweight warning radar." While the Signal
Corps Radar Laboratory at Camp Evans, Belmar, New Jersey , looked over
this LW, the AAF asked in mid July for 100 service test sets and 100 spares.
The AAF doubled the figures before the end of the month, asking for 200
sets from American sources as well as for 200 sets from the British.
These last the Signal Corps contracted for with the Canadian firm, Research
Enter. prises Limited, at $15,000 each, delivery to begin in the following
January." Thus the SCR 602 Type 1 became another British copy, the
last copy of a British radar and the
59 (1) Ltrs, CSigO to ACofS G 2, 25 Feb and 15 May 42,
sub: 100 KW ASV transmitter (British); (2) Ltr, U. S. Embassy, London,
Special Observer [Chaney] to CSigO, 14 Apr 42, sub: LW SetRDF; (3) WD Msg
2332 (CM IN 8254), Eisen. hower to AGWAR, 25 Jun 42. SigC 413.44 SCR602
No. 1, Feb Nov 42 (RB 1526) .
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| last copy of a long
range set (wavelength about one and a half meters, on 212 megacycles) which
the Signal Corps would have to produce for the AAF.
By mid 1942 the pressure for LW radar was becoming tremendous and, as so often happens with new developments, the demand built up suddenly with little advance warning to the laboratory and procurement officers. At the outbreak of World War II the American Army had no really portable early warning radar. It had only the heaviest kind of detectors. Even the mobile 268 and 270 could go only where heavy trucks could transport them. To ship them over water and to land them was no light matter. Obviously their weight and bulk would be handicaps in the island hopping, in the diversified landing and other highly mobile operations which would figure so prominently in World War II. What the Army needed was a detector which could be packaged for hand carrying by a small number of men, landed with the first waves of an assault, and assembled quickly for operation whether in the early stages of an assault or in moving through jungles. LW radar was wanted now, wanted desperately, and the pressure for it led to an amazing variety. Contemplating invasions, the General Staff and the Air Forces wanted at once all the sets they could get (their plans already called for upwards of 1,000 sets). The Air Forces gave them priority over all other sets except IFF radar. They wanted them lightweight, and still lighter, and they wanted sets operating at different frequencies in order to minimize the likelihood of jamming, an art in which the enemy was becoming proficient, especially in the 200megacycle bandwidth of the original British LW. Before the end of the year the LW types |
numbered no less than ten, ten
varieties of SCR 602, either in production or under development by Research
Enterprises, by the Navy, by the International Telephone and Radio, by
the Bell Laboratories, by Radio Corporation of America, by General Electric,
and by the Signal Corps Radar Laboratory. The ten types varied in frequency
from the 212 megacycles of the long wave British prototype to 1,000 megacycles.
They varied in weight, too, from the 1,200 pounds of Type 1, which was
a copy of the British LW, to a 250 pound parachute set (SCR 602 Type 7)
which General Electric was developing."
Thus, though last of the long wave radars, the SCR 602 was not least in any thing but size. Indeed, in its several forms, it came to be one of the most important and numerous of aircraft detectors. Only the first 25 off the production lines of Research Enterprises Limited were exact copies of the British LW prototype. They were designated SCR 602 T1. The next 250 productions differed in design and in designation, which was SCR 602 T6. Thereafter, still further modifications of this Canadian built British copy resulted in yet another change of designation, SCR 602A. Of all these types of the SCR 602, it was Type 8, the unique Signal Corps development, that proved to be the best."' This Signal Corps creation, SCR 602T8, was destined to become the most efficient set of its type, used late in World War II as the AN/TPS 3 (the subsequent Army Navy terminology: T for transportable, P for radar, S for search). For some time prior to 1942 the Signal Corps Lab- el Ground Radar Rpt 1, Wallace Clark & Co. to Gen
Colton, 14 Jan 43, SCR 602. SigC 413.44 SCR 602 No. 2, Dec 42 Mar 43 (RB
1709) .
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| oratories had been
working on 600 megacycle radar, radiating waves 50 centimeters long, intermediate
between long wave and microwave radar. Dr. Harold A. Zahl, a Signal
Corps radio engineer, had developed vacuum tube VT 158 in Signal Corps'
own thermionic laboratory (organized in 1940 in order to turn out radar
tubes of types so complex that industry hesitated to attempt them).
The VT 158 was capable of generating 50 centimeter waves with remarkable
power output in the order of hundreds of kilowatts, remarkable power for
a triodetype tube at that date. The Laboratories tried the tube in
the various sets, such as in the SCR 268. But not until the AAF set up
requirements for an LW did the VT158 really find its place, in SCR 602
T8. Type 8, triumphing, would win even AAF as well as British acclamations,
a triumph indeed for the Signal Corps. Asking for 200 sets, Air Vice Marshal
of the Royal Air Force, R. B. Mansell, told General Colton that "this development
is one of the most important in Ground Radar technique in recent years
and that the designers are to be congratulated in producing a receiver,
display and high power transmitter in a single unit measuring only 42 inches
by 20 inches by 20 inches." SCR 602 T8, or the AN/TPS 3, was Signal Corps'
most substantial contribution to radar after the ancestral Army sets SCR
268, SCR 270, and SCR 271 s3
°a (1) SigC R&D Hist, IV, Pt. 3, proj. 426 D. (2) Historical Report of the Signal Corps Engineering Laboratories (Ft. Monmouth, 1944) , pp. 267, 297 303. (3) Capt Harry M. Davis, Signal Corps Development of U.S. Army Radar Equipment, Pt. III, Long Range Radar, SCR 270 271 (1945 ), SigC historical monograph A 3, p. 81. (4 ) Lt Col Harold A. Zahl and Maj John W. Marchetti, "Radar on 50 Centimeters," Electronics, XIX (January, 1946), 98ff. (5) Ltr, Mansell to Colton, 12 Jun 43, sub: Radar set SCR 602 T 8. SigC 413.44 SCR 602 No. 3, Apr Jun 43 (RB 2027). 264
The remainder of ground radar and all airborne radar in World War II is essentially, as far as the initial stages of research and development are concerned, a story of other institutions such as industrial laboratories and especially the Radiation Laboratory, under Division 14 of the National Defense Research Committee, within the Office of Scientific Research and Development. The Signal Corps kept in touch with the work and took over the final details of development, inheriting of course all the multitudinous adjustments necessary to meet military requirements and to fit the laboratory design for mass production. So it was, as already shown, with SCR 582 and 615. They were the Radiation Laboratory's offspring, although the Signal Corps made many tests and improvements upon them thereafter to suit military needs and saw to all the multifarious details of procurement and distribution. So it was also with two most significant ground radars which the Radiation Laboratory developed for use in World War II: the SCR 584 and the MEW, short for microwave early warning, or in AN terminology, the AN/CPS 1. 265 |
SCR 602 TYPE 8 LIGHTWEIGHT WARNING RADAR |
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