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The TestSignal Corps World War Two August 1, 1951 by Thompson, G. R., D. R. Harris,
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SCR-584 and IFF at Camp Evans |
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Gun Laying Radar
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Gun Laying Radar
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who had been successfully jamming
the SCR 268's there it was the indispensable aid to Allied antiaircraft
gun batteries. The 584, in cooperation with the proximity fuze, which
was actually a tiny radar built into a projectile, was to nip the buzz
bomb menace and find new applications detecting land targets, tanks, and
vehicular convoys at night." More 584's were to be built in World
War II than any other American radar, except the first, the patriarchal
SCR 268.
Subsequent to first tests of the SCR 584 at the Signal Corps Laboratories in December 1941, the XT 1, the experimental prototype of the 584, was returned to the Radiation Laboratory. There the scientists refitted it with a larger six foot antenna dish and stepped up its range." Next, the set went to Fort Monroe, Virginia, for further tests by the Antiaircraft Artillery Board, then under the Coast Artillery Corps. This in March 1942. Any skepticism which had arisen from the first tests at Fort Monmouth in December 1941, when the range of the set had proved disappointing, evaporated during these second tests at the mouth of the Chesapeake Bay. The range was now far greater than the 15,000. yard minimum the service users required. The accuracy was uncanny. And the set was stalwart, even in its laboratory built prototype form. While it stood upon the sea wall at Fort Monroe, overlooking Hampton Roads, a violent storm came up; waves beat against the wall and salt spray doused the XT 1. But the morning after, as the set dried out, it went into action as usual, none the worse for its exposure. The Antiaircraft Artillery .'Baxter, Scientists Against Time,
pp. 114 15, 14 5, 214, 235.
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| Board concluded: "The
Radio Set XT 1 is superior to any radio direction finding equipment yet
tested for the purpose of furnishing present position data to an antiaircraft
director." The Antiaircraft Artillery Board urged the Signal Corps
to standardize the set and procure it in sufficient quantities to supply
one to each Antiaircraft Artillery gun battery.'
Two weeks later General Olmstead recommended that XT 1 be standardized as gun layer SCR 584, simultaneously asking a change in the fifth supplemental national defense appropriation for the fiscal year 1942 whereby 622 sets might be purchased with funds that had been already allocated to another gun laying radar, the SCR 545. This he had urged after a conference in his office a few days before with representatives of General Electric, Westinghouse, the National Defense Research Committee, and the Antiaircraft Artillery Command. General Electric and Westinghouse had been so optimistic as to estimate completion of the 622 sets by July 1943, whereas the bitter fact would be that by then actual delivery would scarcely have begun." There were cogent reasons for the delay of the SCR 584, reasons arising out of both preproduction engineering changes and priority problems during production itself. Some of these the Signal Corps inherited from the Radiation Laboratory; others resulted from the military characteristics which the users desired the Signal Corps to satisfy. " Proj. 1218, Col Bowen, AAA Bd, CAC, 20 Mar 42, sub:
Test of radio set XT 1. SigC 413.44 AAA Bd Rpt 1218 on SCR 584 XT 1 (RB
1524) .
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In
the spring of 1942 the original XT 1, despite its potencies, was still
a long way from a usable practical military set. When the Antiaircraft
Artillery Board members wrote their report after testing the set in March
1942, they commented that the XT 1, being a laboratory model, contained
many makeshift parts which rendered it unfit as it stood for field use.
They recommended some sixteen changes needed to bring the set up to the
military characteristics they desired in the production gun layer. For
example, the Antiaircraft Artillery men wanted tracking to be as automatic
in range as it was in azimuth and elevation (the laboratory model required
hand aided tracking in range). They wanted the antenna mount, its
driving mechanism and pedestal, completely redesigned, a little matter
that was to prove a severe engineering and production problem." They
wanted this set, intended for short range gun laying, to include provisions
for early warning, illuminating upon a PPI type oscilloscope the reflection
of planes many miles away, long before they came within gunshot
In asking this double function, early warning and gun laying combined in one radar, the artillerymen were not just con- °° Neither General Electric nor Westinghouse could
undertake this task. The United Shoe Machine Corporation and the American
Machine Foundry Corporation could not produce in sufficient quantities.
Ultimately, the Chrysler Corporation did the job. As subcontractor to General
Electric and Westinghouse, Chrysler produced for all SCR 584's the trailer
and the precision mechanism to elevate the antenna dish, to stabilize and
rotate the dish itself, and to spin the dipole antenna within the dish
at nearly 2,000 revolutions a minute. Guerlac, Radar, pp. 703 04 (Sec C,
Ch. VIII, pp. 18 19).
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| juring up engineering
and production troubles to harass the Signal Corps. They were following
a precedent. The SCR 545, which the Signal Corps and Western Electric already
had under development for the Antiaircraft Artillery Command, incorporated
this double function, as did the British GL 3. Both the British set
and the American counterpart employed two different frequencies: (1) a
low frequency emanating long waves for long range early warning, and (2)
a higher frequency radiating ten centimeter microwaves for short range
precise gunfire data."
This use of two different frequencies for two quite different functions was a decided complication, which the designers of the 584 discarded. The Radiation Laboratory scientists found that they could extend the range of the microwave XT 1 up to 90,000 yards, quite enough for early warning purposes: Then, as targets flew within about 32,000 yards, the set could begin to serve as a gun layer; the antenna would lock onto the target's reflection, automatically follow it and feed azimuth and elevation data to the gun directors. All this could be done without recourse to long waves. The ten centimeter waves of the 584 could do everything longer waves could do, and do it much better. The SCR584 was freed from the handicaps which inevitably accompanied long waves, siting troubles especially. There were no nulls or blind spots. There were no limitations upon low coverage, a boon when German buzz bombs began to fly in 1944, darting in level courses only a few hundred feet above the '° (1) Memo, Norman Abbott, OCSigO, for 0/C Radar and Aircraft Com Br, 26 Apr 42, sub: SCR 545 mock up. SigC 413.44 SCR 545 No. 1, May Nov 42 (RB 1520) . (2) Guerlac, Radar, p. 705 (Sec C, Ch. VIII, p. 20). |
ground. The 584 tracked
them, whereas long wave radar would have failed utterly.
During the summer of 1942 the Signal Corps Radar Laboratory labored with the production design of the many components of the SCR 584. The laboratory report for August listed as complete the designs for: '1 power unit automatic tracking mount receiver power azimuth and elevation tracking mount amplidyne mount remote video amplifier position indicator Nearly completed were the designs for: modulator pedestal and antenna receiver magnetron positioning control unit Still in the development stage were the designs for: connection diagram equipment assembly wiring interconnection cables Consider for a moment the complexity of such a device. Basically any radio or radar consists of three or four elements: a power supply, an antenna, a transmitter, and a receiver. As contemplated in the summer of 1942, the SCR 584 required about 140 electronic tubes, of about a score of types. The basic transmitter required only one tube, the very powerful cavity magnetron which made centimeter radar possible. The basic receiver did not require an excessive number, a total of 14. But around the receiver transmitter core with its total of 15 tubes thronged a dizzy array of special circuits, each doing a vital job and each re- " SCRL Prog Rpt, Aug 42, proj. S 29.5, p. 40. |
| quiring its own gamut
of tubes. For example:
'z Tubes Azimuth and Elevation Tracking . . . . . . . . . . . . . . . .16 Automatic Tracking Unit . . . . . . . . . . . . . . . . . . . . . ..5 Altitude Converter (Control Unit) . . . . . . . . . . . . . . . 6 Altitude Converter (Power Unit) . . . . . . . . . . . . . . . . 8 Modulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22 Range Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 PPI Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 PPI Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 PPI Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 All this mass, together with operational and maintenance accessories, was packed into a van which housed the operators. The van, its load, which included IFF equipment (RC 184) , together with a trailer containing an electric generator driven by its own gasoline engine, constituted the SCR 584, ten tons in all. Small wonder that one half the total cost of a large 90millimeter antiaircraft gun battery (four guns) went to the radar equipment, valued at $100,000. Despite its superiority, the SCR 584 did not go into production until mid 1943. This was not because of any failure on Signal Corps' part to push matters. It pushed hard from the very first. For example, the Signal Corps succeeded during April and May 1942 in getting the Army to stop production of a searchlight director radar, the ten centimeter SCR 541, and to divert this effort into the 584. The Coast Artillery Corps had long pressed for a new searchlight director, lighter in weight and handier than the original SCR 268. But as the SCR 541 approached production in 1942, the Army found that in some ways the new " Ltr, CSigO to Dir of CESL, 10 Dec 42, sub
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microwave set would be no improvement
over the 268; for example, it would be nearly as heavy. Furthermore,
the 541 tied up components, production facilities, and raw materials which
could be put to better account in the fabrication of the much more valuable
SCR 584. As early as April, therefore, Rives, Metcalf, and others
in the Signal Corps Radar Division in Washing. ton had debated with representatives
of the Services of Supply, Antiaircraft Artillery Command, Ordnance, Westinghouse,
and War Production Board, with a view to recommending cancellation of a
contract which the Signal Corps had made with Westinghouse for some four
to six hundred SCR 541 's. It was Signal Corps' contention that the
radio parts accumulated for the 541, together with raw materials, factory
production facilities such as tools, space, workers, and so on, should
be channeled into the production of the new gun layer SCR 584.'3
This recommendation, as just noted, was carried out.
But another suggestion, the one General Olmstead had made a few days earlier, that 584's be purchased with SCR 545 funds, was not adopted. The order for 273 SCR " Summary of Conf on Radio Set SCR 541 at OCSigO, 29 Apr
42, signed by Col Metcalf. SigC 413.44 SCR 584 XT 1 No. 1, Dec 41 Apr 42
(RB 1386).
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269
| 545's remained,
and they would begin coming off production lines in 1943 a few weeks before
the 584's. No more were ordered, however. Meanwhile, the 584 went on order,
to the number of nearly 3,000, with high hopes from Maj. Gen. Joseph A.
Green, Antiaircraft Artillery commander. "By use of this equipment," Green
commented, "antiaircraft gun batteries will, for the first time, be capable
of directing accurate fire against unseen targets." One set he considered
a must for each gun battery. 74
Neither the 3,000 or so sets which General Green hoped to get in 1943 nor even General Olmstead's more sober figure of 1,175 would attain completion by 1943's end. As already pointed out, priority quirks during 1942 were one cause. Priorities which were supposed to speed the things most needed in this case caused delay. Four test models had been put on order with General Electric in April 1942 for early delivery. They were needed for preliminary tests, which would inevitably reveal desired changes and improvements. These changes would then be incorporated in the subsequent production. The four test models therefore should have enjoyed a priority at least as high, if not higher, than the entire production. But not so. Their priority was much lower. Summer came and went, and yet the four pilot test models failed to appear. General Olmstead thereupon complained to the Army and Navy Munitions Board priority makers that the reason was clear production of the four sets suffered from a lower priority, AA 3, than the rest °' Ltr, Green, Hq AA Comd, to CG AGF, 1 May 42, sub: Increased proc of radio sets SCR 584 in lieu of radio sets SCR 541, with three Inds. SigC 413.44 SCR 584 XT 1 No. 2, Jun Aug 42 (RB1387) |
of the 584 program, which enjoyed
nearly a top priority of AA 1. Illogical that the test models, upon which
the entire production awaited, should languish unrecognized by the very
priority makers who evaluated the rest of the program at AA 1. The
commanding general of the Army Ground Forces was aroused. He particularly
wanted the first four sets in order to initiate training. Otherwise,
the first procurement sets now expected in April 1943 would have no one
who knew how to operate them, however desperate the need of combat Antiaircraft
Artillery units. He asked General Somervell to grant the manufacturer,
General Electric, top AAA priority."
One reason for the low priority was secrecy. Priority makers in the Army Navy Electronics Production Agency and the War Production Board could not get the facts. The Signal Corps' contracts with manufacturers stipulated, for example, that delivery schedules and other data touching the 584 could be made only to Signal Corps members. Such restrictions arose again and again, whenever secret equipment was procured. Representatives of Chrysler, General Electric, Westinghouse, and Fruehauf, among others, all complained of the trouble they encountered when seeking assistance from the Army Navy Electronics Production Agency and the War Production Board toward getting the 584's produced. Why? Because they were forbidden to provide these agencies with the delivery schedules of highly classified Signal Corps equipment. Yet how could the priority judges make '° (1) Ltr, CSigO Chairman of ANMB Priori ties Sec, 24 Aug 42, sub: Priorities on radio set XT 1 A (SCR 584); (2) Ltr, CG AGF to CG SOS, 8 Sep 42, sub: Priority rating on contract for radio sets XT 1 (A). SigC 413.44 SCR 584 XT 1 No. 3, Sep Dee 42 (RB 1523). |
| equitable judgments
if they could not be adequately informed? 'e
The Signal Corps' complaint about the lower priority of the first four 584's touched off a minor explosion over the GL radar program. The explosion uncovered some interesting things, as, for example, the fact that the allocation of machine tools to electronic production was nearly nil. The men who made allocations were vastly impressed by the need for aircraft, and they allotted 60 percent of all machine tool facilities to aircraft plant expansion in 1941 1942, but none to plant expansion for the manufacture of the electronics equipment which the aircraft needed. Yet this equipment represented a large percent of a bomber's cost (it would approach 33 percent by the war's end). Likewise, ordnance got large allocations, but not GL radar, though, as pointed out earlier, it would soon constitute one half the cost of a 90 millimeter gun battery. Not till late 1942 did Signal Corps production needs begin to win recognition among machine tool allocators, when the Corps was granted a parsimonious 4 percent. No wonder manufacture of the huge radars and of other complex electronic devices lagged, while the Army screamed for them and glowered at the Signal Corps as '° Memo, George P. Allison, Electronics Br OCSigO, for Allison, 9 Mar 43. SigC 413.44 SCR584 XT 1 No. 4, Jan Mar 43 (RB 1707). Similarly, production of spiral four desperately needed for the North African invasion lagged in the summer and autumn of 1942 because "the secrecy surrounding the operation was so great that this requirement could not be discussed sufficiently to obtain the needed priorities." Here the block was the secrecy blanketing the invasion rather than the equipment. But the adverse effect on production was the same. Capt Sidney L. Jackson, Fixed Wire, NATOUSA: Chapter I of Theater Fixed Networks (1944), SigC historical monograph E la, p. 12. SigC Hist Sec File. |
the most laggard of suppliers.
Ignorance and secrecy doubtless helped to prolong the delay. Everyone
knew airplanes needed aluminum and guns needed steel, together with myriads
of machine tools to fabricate the metals. But not everyone knew about
the electronic devices that controlled and guided the massive metal mechanisms
coming off aircraft and ordnance production lines. It was easy to
see the growing body of the war juggernaut and add to it, but it was not
so easy to perceive that it had eyes and a network of electronic nerves
of radar. Besides, many of the electronic components, and all of
the radar, were secret. Most men, even those in uniform, were not permitted
to see it, or only dimly.
Airmen concerned over air defense had for many months been making clear their need for electronic equipment. Colonel Saville, for example, had been especially insistent, with the strong support of the Secretary of War. Yet it was not till late 1942 that General McClelland in AAF headquarters asked General Arnold to demand more money, more factories, more tools for electronics, just as the AAF chief had done months before for aircraft. By now, late in 1942, the artillerymen began to clamor too, having just begun to learn the possibilities which GL radar offered. At the same time the Air Forces, backed by Secretary Stimson himself, had gotten the best priorities obtainable for much of their airborne electronic needs. But the priority makers had not yet given much thought to ground radar for artillery and very little thought at all to the necessary preliminaries to the allocation of raw materials and machine tools. At the level of the joint Chiefs of Staff, Army Ground Forces needs in electronics |
| were consistently overridden
during 1942 by the Navy and the Air Forces."
During the autumn of that year, correspondence flew back and forth between the heads of the Antiaircraft Artillery and the Army Ground Forces recounting the significance of the new gun laying and other ground radars in a manner which reveals how new it all was to the ground Army. The high ranking correspondents took pains to explain the sets, what they were, and what they did. The sets, they wrote, were essential for protection of harbors and of invasion efforts generally. Mighty important, then, was this new application of radar if overseas invasions must depend on it. General Eisenhower would soon be writing back from North Africa saying that he must have something better than the SCR 268 for gun laying, a refinement for which the 268 was never intended, but for which it proved better than no radar at all." Thus the land Army was slow finding out how badly it needed gunlaying radar, just as the Air Forces had not appreciated airborne radar until the turn of 1940 1941. And until the Army found out its needs and brought pressure to fill them, the funds and the support which the Signal Corps had to have in order to develop and produce the equipment simply were not forthcoming. When the Army belatedly found out what it wanted and how '° "In the Precedence Conferences, Joint Communications
Board, JCS, the Ground Forces were consistently voted down," commented
Col. Byron A. Falk, who was the chief of the Precedence Branch of the ANEPA
during the last half of 1942. OCMH Critique of MS, p. 29. SigC Hist Sec
File.
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badly, then it wanted the equipment
immediately, if not sooner. Naturally and lamentably, it had to wait,
and the Signal Corps had to endure its fulminations, a state of affairs
to which military supply agencies must, in the nature of things it seems,
become resigned.
On 8 October General Green, in the headquarters of the Antiaircraft Artillery Command, complained to the Commanding General, Army Ground Forces, that on information from the Chief Signal Officer he had discovered he would not get any GL's, either SCR 545 or SCR 584, until some six or seven months after the delivery date originally promised. If the sets arrived too late, it would be too bad, to state it mildly. As Green put it If radar equipment is to be used to advantage in this war, the development and procurement of newer types of radar equipment must be pressed to the utmost, and the importance and urgency of this work should be impressed on all concerned. It is strongly recommended that every effort be made to expedite the antiaircraft radar program, both in development and procurement, and that particular stress be placed on the procurement of gun control sets and the development and procurement of a new searchlight control set. General Moore, writing for the Commanding General, Army Ground Forces, agreed. Adding details about other Coast Artillery radars, the 296 and the 582 (whether for his own enlightenment or for that of General Somervell to whom he addressed a first indorsement on Green's letter), he attributed the delay to the action of the priority makers. This procurement program [of the 296, 545, 582, and 584] was disrupted by the action of the Precedence Committee of the Com- |
| bined Communications
Board which set up a precedence list for the manufacture of all radar equipment
and relegated Coast Artillery radar procurement to Categories III to IX
inclusive, thereby delaying all Coast Artillery radar manufacture for many
months. By this action the procurement of Radio Set SCR 296 was stopped
and certain critical parts were diverted for the manufacture of radar equipment
in categories I and II [doubtless aircraft radar] in spite of the fact
that a contract had been let, manufacture was in progress and many of the
SCR 296's were nearing completion. Similar action has delayed the
initiation of procurement of Radio Sets SCR 584 and 545 several months.
General Moore urged Somervell to take steps "to correct the existing situation" and to jack up the precedence of these GL radars "to a point which will assure uninterrupted procurement in the immediate future." He regarded such sets as vital safeguards in the invasions which the military chiefs were contemplating. "Our harbor defenses," he wrote, "must have the necessary antiaircraft fire control apparatus to assure a safe haven for allied naval forces. Our antiaircraft units must be supplied with gun laying radars before they can enter combat with any reasonable prospect of success." Somervell, no authority on electronics, sought information from the electronic section of his empire, the Signal Corps information "upon which a reply may be drafted." Colton drafted the reply. So far, he showed, the delays at which Green and Moore chafed were not all the consequence of priority maladjustments at the production level. They were rather a consequence of a priority oversight at a lower, and earlier, stage in the development that resulted in insufficient machines to tool up production plants. The changes which the Antiaircraft 330450 0 57 19 |
Artillery Board had wanted made
in the original XT 1, when it had tested the sets in March 1942, called
for $10,000,000 in tools alone, before the raw materials were assigned
and before production could even begin. Yet the Signal Corps had been favored
with no such tool allotment. What it had gotten for its manufacturers
it had obtained by diversion from other services. That had been true
till very recently when the Signal Corps had been allowed a 4percent tool
allotment, still ridiculously small when one considered the vastly larger
percentage electronics shared, on a cost basis, with the rest of the war
production effort .'e
The little matter of low priority for the pilot models was only one obstacle. There were many others: shortage of raw materials and critical components, such as tubes, for example, which consumed such rarities as tantalum, molybdenum, and tungsten and whose manufacture was most delicate and exacting. Then there were selsyns, tricky little electric motors and coordinating mechanisms which enabled the different parts of a large robot to keep in perfect step, its motions perfectly synchronized. The order for 584's was going to require some 60,000 selsyns immediately. Still another tricky component, rejoicing in the name amplidyne, consisted of electrical motors and gears which enabled heavy platforms bearing radar antennas and mounts to rotate, smoothly, precisely, whether fast or slow. The obstacles to production scheduling which all these complexities presented °8 Ltr, Green to CG AGF, 8 Oct 42, sub: Radar Development, with 1st Ind, Gen Moore, Chief of Ground Rqmts Sec (writing for CG AGF) to CofS, 22 Oct 42; 2d Ind, Somervell to CSigO, 31 Oct 42; 3d Ind, Colton, Actg CSigO, to CG SOS, 24 Nov 42. SigC 413.44 Gen No. 3 (RB 1533). |
| Metcalf summed up for
General Somervell late in September 1942: s°
Delivery of these sets [2,750 SCR 584's and 273 SCR 545's, by General Electric and Western Electric respectively] was previously scheduled to be completed by the end of 1943. However, the production of Radio Set SCR584, which comprises the bulk of this procurement, is contingent upon a great many uncertain factors, for example, the extension of plant facilities and provision of assembly of these sets and for production of the special semi trailer and precision antenna elevating and tracking mechanism, the allocation of various critical raw materials and procurement of such critical component parts as tubes, selsyns, amplidynes, etc. Accordingly, on the basis of the best information now available, the Chief Signal Officer estimates that no more than about eleven hundred seventy five (1175) Radio Sets SCR 584 can be safely counted upon for delivery by the end of 1943. Thus, production of Signal Corps equipment such as this giant microwave gunlaying radar was big business indeed, in which many an agency participated. In one of the early procurement debates respecting the SCR 584 there sat representatives of the Signal Corps Radar Laboratory, the Navy, the War Production Board, the National Defense Research Committee, Westinghouse, General Electric, and Chrysler. Rives and Elder presided, while Dr. Bowles, Secretary Stimson's radar consultant, attended." Eventually, the difficult mount de- 80 (1) Ltr, CSigO to CG SOS, 25 Sep 42, sub: Rqmts for
radio sets SCR 545 and SCR 584. (2 ) Ltr, CSigO to Dir of SCRL, 2 Oct 42,
sub: Selsyns required for radio set SCR 584. A single SCR 584 required
16 selsyns, 8 motors, and 2 amplidynes. Ltr, Dir of SCRL to CSigO, 7 Sep
42, sub: Amplidynes and selsyns. SigC 413.44 SCR 584 XT 1 No. 3, Sep Dec
42 (RB 1523) .
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sign, with all the exacting requirements that daunted several manufacturers, was accepted by the Chrysler Corporation. General Electric and Westinghouse, each with a contract for 1,375 sets, began production, and by May 1943 the first production SCR584 was to arrive at the Signal Corps Radar Laboratory. 12 |
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