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The Invention that Changed the World: How a small group of radar pioneers won the Second World War and launched a technological revolution
by Robert Buderi
- By Robert Buderi, Simon & Schuster (C) 1996 Robert Buderi
All rights reserved.
- BOOK EXCERPT, CHAPTER ONE
- The Most Valuable Cargo
- "When the members of the Tizard Mission brought one
to America in1940, they carried the most valuable cargo ever
brought to our shores." --James Phinney Baxter III, Official
Historian of the Office of Scientific Research and Development
- The black japanned metal deed box could just be seen above
thewartime throngs on the shoulder of a railway porter. The small
container bobbed along frustratingly out of reach, as Eddie Bowen
zigzagged throughthe crowd in hot pursuit. Only moments before,
sometime around 8:15 themorning of August 29, 1940, the Welshman
had arrived at London's EustonStation with the box safely in
his possession. Innocently, Bowen hadhanded it to the porter
while gathering up his remaining luggage, thenwatched helplessly
as the man headed off to find the 8:30 train to Liverpoolwithout
waiting for his customer.
- As he struggled to keep the porter in sight, Bowen would
not have drawn much attention from busy Londoners. In stature
and build he blended into a crowd and would have seemed like
any other young man in a hurry. Only his face set him slightly
apart. Wavy hair cut short crowned a wide forehead and jaw and
gave his head a squared-off look. Old photographs often show
an infectious grin spanning the broad tableau. But one could
also imagine the weathered visage locked in determination--and
that August morning Bowen had reason to be concerned. Just five
days short of the war's first anniversary, Britain faced one
of her most desperate hours. Bombs were falling nightly on Liverpool,
Nazi armies ringed the country from the Norwegian coasts down
to France, and an invasion was expected within weeks. As Bowen
knew, the seemingly ordinary solicitor's deed box--now visible,
now not in Euston's morning rush--held the power to change the
course of the conflict.
- Inside lay nothing less than the military secrets of Britain--virtually
every single technological item the country could bring to bear
on the war. Had some freak accident burst the lock off the chest,
the platform would have been awash in blueprints and circuit
diagrams for rockets, explosives, superchargers, gyroscopic gunsights,
submarine detection devices, self- sealing fuel tanks, even the
initial germs of the jet engine and the atomic bomb.
- Among these treasures, nothing carried the all-pervasive
importance of the resonant cavity magnetron, Britain's most closely
guarded secret. The black box contained one of the first 12 production
copies of the mysterious device--probably the only piece of hardware
it sheltered. Small enough to fit in the palm of a hand, the
magnetron looked like a clay pigeon used in skeet shooting, with
a few wire leads thrown in. Yet, it could spit out pulses of
microwave radio energy--on a wavelength of about 10 centimeters--so
powerful conventional scientific wisdom still put anything like
it years off.
- The magnetron was a radar transmitter, one with the potential
to bolster British military capabilities almost across the board
and give the country the upper hand in what already seemed like
a technological war: no one in the country knew it, but the Germans
were generally ahead in the radar race until the device arrived
on the scene. More immediately to the point, as Bowen chased
the porter across the Euston platform, the strange copper disk
offered a way to invigorate the strapped British defenses that
had been coping with Luftwaffe bombing onslaughts the past six
weeks--a softening up before Hitler's planned invasion. Radar,
or radio distance finding as Bowen's countrymen called the technology,
formed the backbone of these defenses. Imposing towers up to
350 feet tall--the Chain Home station network--lined the country's
south and east coasts to provide the only effective early warning
of German attacks. These electronic sentries operated round-the-clock,
rain or shine, sending out pulses of radio energy and picking
up the faint echo from enemy aircraft more than 100 miles away.
Radar was basically all the outgunned country had that enabled
Fighter Command to husband its too-thin air resources. Without
it, planners would have to consider keeping standing patrols
aloft, wasting fuel, needlessly fatiguing pilots, and risking
being in the wrong place at the wrong time.
- Magnetrons represented the next crucial step--a leap, really--in
the evolution. The Chain Home stations worked well in daylight,
when a pilot's sharp eyes could correct for the several-mile
error range inherent in their long operating wavelengths of between
10 and 13 meters. But to cut losses, the Germans were widely
expected to move soon to concentrated night attacks, when visibility
was slashed dramatically. The British had tried to supplement
the chain by installing short-range systems inside fighter aircraft--the
idea being once the main network got the interceptors close,
airborne radars could carry them the rest of the way--but these
remained clumsy and inaccurate. Only the magnetron seemed certain
to keep the British well ahead of the game. Its 10-centimeter
transmissions ran a mere fifteenth those of standard airborne
radars. Fitted into nightfighters, such a device would generate
sharper pulses in a tightly concentrated parcel of energy that
would fan out far less during the brief journey to an enemy aircraft
and back, making it immensely easier for pilots to home in on
their quarry even on the darkest nights.
- That, though, was only the beginning. Although the magnetron
had been invented just eight months earlier by two physicists
at the University of Birmingham, its portability and versatility
soon summoned visions of putting the beleaguered nation on the
offensive. Aircraft equipped with centimeter radar might pick
out U-boat periscopes rising under cover of darkness. Lancasters
and other bombers could use the extremely short waves the magnetron
produced to illuminate the way through the thick cloud cover
obscuring Hitler's forces and factories on the European continent,
keeping planes flying on days the Royal Air Force would normally
- Yet for all the device's promise, a series of technical glitches
continued to plague its development--the most serious stumbling
block being uneven power performance. British industry, with
its limited production capacity, and already under the threat
of bombardment and invasion, simply could not trust that it alone
possessed the capability for correcting the problems and churning
out magnetrons in the numbers needed for war.
- It was this overriding concern--not just in regards to the
cavity magnetron but extended to all the devices in the black
box--that brought Bowen to the Euston platform that August morning.
Though still four months shy of his 30th birthday, the Welsh
physicist ranked as one of Britain's defense pioneers. For the
past five years he had labored in some of the island's most isolated
spots--sometimes night and day--to develop the Chain Home network
and the country's first crude airborne radar systems. As a leading
defense scientist he had been tapped to join a top secret government
mission aimed largely at convincing the still-uncommitted American
government and key industrial officials to pick up where British
resources left off. The mission was to sail from Liverpool that
- To pave the way for the venture, a special team had spent
the first two weeks of August rounding up the black box's contents.
Bowen himself had visited the General Electric Company research
laboratory in the London suburb of Wembley, where he picked out
the best working model of the first dozen magnetrons made. He
had then carried his selection unescorted on the Underground
to the Ministry of Supply headquarters between London's Victoria
Embankment and the Strand. At the Ministry, the precious cargo
had been placed safely in the black box, remaining under lock
and key until the evening of the 28th, when Bowen returned to
escort the entire booty to Liverpool. A guard delivered it via
the arched doorway on the ministry's back steps. From there,
Bowen hailed a taxi to whisk him to the Cumberland Hotel, near
Euston at historic Marble Arch.
- Because the box would not fit in the hotel safe, Bowen had
spent the night with England's greatest military secrets wedged
under his bed. In the morning, to add to his discomfort, the
cabby taking him to the train station would not allow the small
chest inside the taxi, insisting it be placed on the roof. The
Welshman had thought all was well when the cab finally reached
Euston--but then the fast-footed porter had prolonged his unease.
- Bowen didn't catch up with the man until they reached the
train. At this point, he knew only that a first class seat had
been reserved. But when he found his place, it appeared an entire
compartment had been set aside: the blinds were drawn and reserved
notices placed on the windows. Intrigued, Bowen sat down to wait
for the train to leave, figuring all would become clear on the
- A few minutes before departure, a well-dressed and exceptionally
trim man with a public school tie entered the compartment. With
scarcely a glance around, the man took up the seat diagonally
across from Bowen and began reading a newspaper. The mysterious
companion didn't speak until a few minutes after the train began
edging out of the station--when some late- comers opened the
door, happy to have found an empty cabin.
- "Out," he ordered. "Don't you see this is
- Bowen was struck not so much by the man's words as the commanding
tone of the delivery. "The would-be intruders wilted,"
he later recalled, "and we had no further interruptions."
At that moment, for the first time in a harrowing 16 hours or
so, Bowen realized, too, that his precious cargo carried some
form of protection.
- The journey passed in silence. When the train finally pulled
into Liverpool's dockside station, Bowen didn't budge from his
seat--following instructions to stay put until an Army escort
arrived to pick up the box. His compartment mate also remained
in place, ostensibly absorbed in the paper.
- At last, a dozen fully armed soldiers marched down the platform
and came to a glorious, rifle-slapping halt alongside the car.
A sergeant barked some orders, put the group at ease, and dispatched
three men to collect the cargo. Bowen watched as Britain's technological
pride and joy was carried outside, hoisted onto some shoulders,
and marched back down the platform. The display of military exactitude
eased the young physicist's mind, but not totally. Telling the
story later, he joked, "I was beginning to feel that things
were well looked after. Alternatively, if this was the enemy
making off with Britain's secrets, they were making a spectacular
job of it."
- Through all the commands and gesturings, Bowen's mysterious
cabin mate still had not uttered not a word. Now the man rolled
up his paper, and with a slight nod at his fellow traveler, took
- Bowen also roused himself and shuffled off along Gladstone
Dock to find his ship, the Duchess of Richmond. On board the
Canadian liner, he joined the main body of what was formally
called the British Technical and Scientific Mission to the United
States. Informally, and far more commonly, the venture was known
as the Tizard Mission, after its organizer Sir Henry Tizard,
rector of the Imperial College of Science and Technology and
chairman of the government's key scientific committee on air
- Tizard, an Oxford-trained chemist, had already made his name
as one of Britain's shrewdest scientific visionaries. Beginning
in 1935, his Committee for the Scientific Survey for Air Defense
had pushed radio direction finding over all other competitors--sound
mirrors, infrared detection, balloon barrages. In late 1939,
recognizing the need for American assistance in developing radar
and other military technologies, he had conceived the idea of
an exchange mission with the United States. His proposal had
received strong support from Archibald Vivian Hill, the influential
Nobel Laureate and joint secretary of the Royal Society, who
had gone to America early in 1940 to grease the wheels on the
other side of the Atlantic.
- The plan hinged on making a full disclosure of the kingdom's
technical secrets in the hopes that America, even if it stayed
neutral, would gear up its immense industrial machine to help
develop and produce them. Initially, many British authorities
wanted to trade secret for secret--seeing the exchange as a way
to pry loose details of the coveted American Norden bombsight.
But after months of in-fighting and wrangling, new Prime Minister
Winston Churchill, who had taken over the governmental reins
in May 1940 on the heels of the German blitz into western Europe,
decided to make the offer with no strings attached--the prevailing
view being that American cooperation would be more complete if
there were no attempt to barter secret for secret.
- So complete was the offering that by the time Eddie Bowen
walked along the Liverpool docks that August afternoon, only
two items of any note had been held back--some particulars of
the jet engine, and details of the latest German magnetic mines
used to block British harbors. Besides the crucial cavity magnetron,
nearly everything about radar could be found in the black box;
and several containers of working sets and components apparently
had been sent through separate channels to supplement its contents.
- Tizard deliberately restricted the mission to just seven
members-- counting himself. Bowen was his hand-picked radar expert.
Cambridge University physicist John Cockcroft, architect of one
of the world's first proton accelerators, would brief the Americans
on the remainder of the technological booty, as well as a few
isolated aspects of radar. In addition to the two scientists,
each of Britain's three services--the Royal Air Force, the Admiralty,
and the Army--contributed an officer with recent combat experience
who could talk about military needs. The last member was Arthur
Edgar Woodward-Nutt, an Air Ministry official who served as the
- Tizard and one of the mission's military representatives,
Group Captain F. L. Pearce of the Royal Air Force, had flown
across the Atlantic a few days ahead of the main body to pave
the way for the exchange. But the other members would make the
crossing with Bowen on the Duchess.
- With the black box safely escorted off the train, the Welshman's
responsibility had ended. Aboard ship, Woodward-Nutt, the sole
member of the entourage allowed access to the chest during the
voyage, saw the secret cargo locked in the strong room. He arranged
to meet the third officer, who held the keys, in the event of
a German attack--so they could dump the rich bounty overboard.
- The ship left its mooring that evening, inching down the
Mersey river toward the Irish Sea. An air raid hit Liverpool,
with a few bomb splashes rocking the boat right after dinner,
so the crew anchored down for the night near the river mouth.
The Duchess finally set sail the next morning, Friday, August
30. Minesweepers escorted the liner the rest of the way through
the Mersey, which was littered with wrecked boats. Later, two
destroyers took over, shepherding the liner through heavy seas
for a few hours until she built up speed and opened a zigzag
course to elude any lurking U-boats.
- Tizard mission members passed time aboard ship in the usual
way: reading, listening to BBC broadcasts, playing deck games
and bingo, watching films in the ship's cinema, and taking brisk
walks in the cold North Atlantic air. About 1,000 sailors also
took berths on the Duchess, bound to pick up the first aged U.S.
destroyers consigned to Britain in exchange for the rights to
various naval and air bases. The well-known Cockcroft lectured
the bored servicemen on a scientific subject he felt safe to
discuss, since it couldn't possibly have a bearing on the war:
nuclear energy. He impressed his audience by pronouncing that
a cupful of water held enough atomic power to blow a battleship
a foot out of the sea. As a separate exercise, Cockcroft also
calculated the black box's chances of sinking with the ship should
they be struck by an enemy torpedo--and concluded the buoyant
cargo would stay afloat. Holes were drilled in each end.
- On the evening of September 5, the ship pulled off Newfoundland's
Cape Race. The following morning dawned calm and misty as she
slipped into Halifax Harbor. Bowen remembered spying an American
armored vehicle, "submachine guns bristling from every orifice..."
Woodward-Nutt, though, recorded spending several hours on the
phone with the British Embassy in Washington, arranging for a
Canadian military guard to take the secret equipment to the U.S.
border, where it would be turned over to American authorities
and transported to the embassy. He personally saw the equipment
off early the next day.
- At Halifax, Bowen split off from the rest of the group, heading
to Ottawa to arrange for officials from Canada's National Research
Council to join the exchange--and to locate some of the equipment
presumably shipped over earlier. He would catch up with the others
in Washington a few days later. The rest of the mission left
Nova Scotia by rail at 8:45 the morning of the 7th--changing
trains in Boston and arriving in Washington at 5:30 the next
- The group met Tizard at the Shoreham Hotel, overlooking Rock
Creek Park near the British embassy in northwest Washington.
"I was a bit shaken," writes Woodward-Nutt, "to
find that the samples and documents that I had seen off so carefully
at Halifax had not yet arrived." It took a series of telephone
calls to locate the cargo; and the precious container, bearing
the cavity magnetron and the technological hopes of an entire
nation, finally arrived at the embassy on Monday, September 9,
1940. There, it was locked in the wine cellar and given to the
care of the Ambassador's butler, who as far as could be determined
possessed the only key.
- The Americans anxiously awaited the Tizard mission. It hadn't
seemed that way at first. Sir Henry had arrived in Washington
on August 22, expecting a welcome mat arranged by A.V. Hill.
Instead, he complained to his diary: "No administrative
arrangements made for my Mission. No office, no typists, etc.
Felt rather annoyed."
- The bad taste had not lingered, however. The next day, Tizard
huddled with Navy Secretary Franklin Knox to establish the ground
rules for the exchange. On the 26th, he received an audience
with FDR, who welcomed him but explained that political considerations
prevented the U.S. from sharing details of the Norden bombsight.
Most important of all, two days later over dinner at the Cosmos
Club, an exclusive Lafayette Square haven for the inner circles
of science, art, and literature, Tizard met Vannevar Bush.
- With his raw-boned face, wire rim glasses, and piercing gaze,
the charismatic Bush in many ways formed Tizard's mirror image
on the western side of the Atlantic. Scion of seven or eight
generations of Cape Cod Yankees, and equipped with a tell-tale
Northeastern twang, he could be confidently stamped Made in America--just
as Tizard, with his own accent, pince-nez, and somewhat aloof
manner, left no doubt of his origins. Like Tizard, Bush hid a
hard edge behind a calm demeanor. Like Tizard, too, he was a
scientist--an M.I.T. electrical engineer who had pioneered early
computing--responsible for marshaling civilian science and technology
for war. Few men would match his power during the war years,
as his dominion grew to include medical research, the atomic
bomb, and virtually all forms of chemical and conventional warfare.
"Of the men whose death in the summer of 1940 would have
been the greatest calamity for America, the President is first,
and Dr. Bush would be second or third," noted the multimillionaire
investment banker Alfred Loomis, a Bush friend destined to play
a crucial role in the radar story.
- Bush had pitched his tent in the nation's capitol since late
1938 as president of the prestigious Carnegie Institution of
Washington, a private research organization endowed by steel
baron Andrew Carnegie. However, he dined with Tizard as chairman
of the National Defense Research Committee, established by presidential
order two months earlier to mobilize civilian scientists for
war. Bush had created the N.D.R.C. almost through sheer personal
will. During World War I, working on submarine detection, he
had seen first-hand the distinct lack of cooperation between
civilian scientists and the military. So he conceived the idea
of establishing a new national committee to bridge the gap. Maneuvering
deftly through theWashington maze, he drew on the influential
lawyer Oscar Cox, then Commerce Secretary Harry Hopkins, to negotiate
an interview with the President. Bush entered the Oval Office
on June 12, 1940, entering the meeting carrying a single sheet
of paper with a four-paragraph sketch of the proposed agency.
Less than ten minutes later, Roosevelt had signed on: "That's
okay," he told the feisty engineer. "Put `OK, FDR'
- Some Washingtonians complained that the N.D.R.C. represented
a power grab by a small band of scientists and engineers working
outside established channels. Bush made no bones about it. "That,
in fact, is exactly what it was," he once admitted. But
his personal mandate from Roosevelt extended to helping the country
"excel in the arts of war if that be necessary." And
while he respected the military's turf, Bush made certain people
never forgot who had issued his orders.
- The Carnegie president moved quickly to solidify his power
base, bringing in as key lieutenants some old friends and confreres:
M.I.T. president Karl Compton, Harvard University president James
B. Conant, and Frank B. Jewett, president of the National Academy
of Science and Bell Telephone Laboratories. The scientific cabal,
Bush co-conspirators in conceiving the N.D.R.C., immediately
launched a survey of Army and Navy research activities and began
compiling a list of technical jobs to take over-- either because
the work had not yet gotten underway, or because once the U.S.
abandoned its neutrality the military would have to drop them
to meet more pressing demands. At the same time, the men contacted
some 775 universities, industrial labs, and non-profit institutions--compiling
a roster of personnel and facilities in scientific arenas likely
to affect the war. This was "the Bible."
- By the time Bush dined with Tizard on August 28, he had mustered
his forces into several main divisions, covering everything from
armor and ordnance to communications, explosives and patents.
Radar matters fell to Karl Compton's Division D--instruments
and controls. Since the military survey showed that the Army
and Navy both had already made great strides in meter wave radar,
the N.D.R.C. adopted as its domain the vague promise of microwaves--naming
Alfred Loomis chairman of a special Microwave Committee, Section
D-1. It was a natural, insider's choice. Loomis sat on the M.I.T.
board and had contributed funds to the institution's general
microwave research. Moreover, he was a noted amateur physicist
who conducted his own fledgling microwave radar studies on a
private estate outside New York City--and therefore appreciated
the challenges in store.
- While the various N.D.R.C. divisions could probably all delve
into the British black box and find interesting treasures, it
was on the microwave radar front--a top priority for both groups--that
Bush and Tizard found their perfect match. The American possessed
the presidential authority to develop the technology. The Englishman
had the cavity magnetron.
- When the two men met at the Cosmos Club, Bush remained unaware
of the magnetron's existence. But he made it his business to
know what was going on--and had been tipped off, probably by
A. V. Hill, to certain generalities of the British radar bonanza
long before the mission arrived. Face to face at last, however,
he felt compelled to advise Tizard that although the N.D.R.C.
welcomed a meeting with the British mission, the two groups should
keep their distance until the U.S. military opened the talks:
that way, Washington insiders could not accuse them of plotting
some sort of conspiracy. Once the exchange was formally underway,
Bush would take steps to correct the situation.
- Tizard took the cue. While waiting for the N.D.R.C. to be
let in on the talks, he and Bush met several times "behind
the barn," as the wily engineer called it. It is not clear
what transpired between the two men, so alike and so seemingly
destined to forge a new bond. Most likely they covered general
logistics, hinting at the shape of things to come in the clubby
ways at which both were so adept. In any case, as his entourage
began sharing extensive details on longwave radar and other subjects
with U.S. military representatives in early September, Tizard
managed to give the impression of an extraordinary advance without
revealing the secret of the cavity magnetron--even when the Navy
showed its visitors an experimental, extremely low-powered, 10-centimeter
radar system. It wasn't until September 16 that Vannevar Bush
won formal approval from both the Army and Navy for the N.D.R.C.
to join the exchange. Only then did Sir Henry play his trump
- The British disclosed the existence of the cavity magnetron
at the first extensive contact between the Tizard Mission and
N.D.R.C. members--a party hosted by Alfred Loomis the night of
September 19 at the Wardman Park Hotel. The rambling 1,800-room
megacomplex dominated the southeast corner of Connecticut Avenue
and Woodley Road, just a stone's throw from the Shoreham, where
Tizard had set up shop in an office suite swept daily for bugs.
- Eddie Bowen and John Cockcroft showed up at Loomis' rooms
around nine o'clock. Bowen had returned from Canada the night
of the 11th--and the two men had spent the past week detailing
British longwave radar accomplishments to American military officials
at the War Department and nearby Naval Research Laboratory. Among
the disclosures were technical details of the Chain Home early
warning stations already doing yeoman's service in the Battle
of Britain; radio homing beacons; submarine-hunting radars; and
Identification Friend or Foe, a radio signal carried in planes
designed to help radar operators distinguish "friendlies"
from the enemy.
- The exchange had proven interesting, but only marginally
useful to the British. Going into the meetings, both sides were
convinced the other could not possible possess radar. But as
they quickly discovered, each had invented the technology independently
in the mid-1930s, within a few months of each other: in fact,
the British Chain Home Low, which guarded against low-flying
planes, turned out to be virtually identical to the U.S. Navy's
CXAM radar, operating on the same frequency and sharing several
other technical features. As far as anything the British could
use in the war effort, however, pickings were slim. The Americans
did enjoy an edge in receiver technology. But at the same time,
the U.S. had not developed airborne radars or anything like IFF--and
the few other systems in existence had seen little operational
- If Bowen and Cockcroft were hoping for more on the microwave
front from contact with Loomis' group, they were not disappointed.
Vannevar Bush himself was not on hand: he preferred to delegate
authority and leave his lieutenants alone. However, besides the
host the small gathering included Carroll Wilson, Bush's personal
assistant and alter ego, Karl Compton, and Admiral Harold Bowen,
director of the Naval Research Lab. The admiral, who had earlier
authored an internal memo discounting the idea of British radar,
apparently harbored ongoing misgivings about the exchange. He
appeared to drink heavily at the party, but Compton suspected
his colleague of feigning to be farther gone than he really was
in order to avoid sharing information.
- The British sensed such misgivings. "I still remember
the rather doubtful opening with the U.S. officers suspicious
as to whether we were putting all our cards on the table,"
Cockcroft remembered. The Americans showed their hand first,
though, detailing an exhaustive survey of the nation's general
microwave research that Loomis and Compton had conducted over
the summer. It soon became clear to Bowen and Cockcroft that
for the 10- centimeter waves emitted by the cavity magnetron,
Bell Telephone Laboratories and General Electric both could contribute
a lot to receiver technology. Bell Labs, Stanford University,
and the Massachusetts Institute of Technology, they were told,
also conducted advanced research in microwave waveguides and
horn-shaped antennas. The British physicists found the information
exceedingly helpful in pinpointing areas to visit.
- Their hosts, however, confessed to being at loose ends trying
to find a transmitter tube able to generate enough power to make
for a feasible centimeter radar system. By the time of Loomis'
party, a stymied Microwave Committee had steeled itself to write
a report--a sure sign, as one member explained, "that we
didn't know what to do next."
- Bowen and Cockcroft quietly pulled out the cavity magnetron--by
one account, they typically carried the device in a small wooden
box whose lid was fastened by thumbscrews--and told their dumbfounded
listeners that it could generate 10 kilowatts of power at ten
centimeters, roughly 1,000 times the output of the best U.S.
tube on the same wavelength. In one fell swoop, the disclosure
dispelled any tension left in the room--and from that point on,
things went smoothly.
- "It was a gift from the gods we disclosed to Alfred
Loomis and Karl Compton," Bowen boasted late in life. The
financier swiftly embraced the offering, inviting his new-found
friends to Tuxedo Park, the posh retreat about 35 miles northwest
of New York City where he had built his private laboratory. It
was time for mere mortals to get to work.
- The Invention
that Changed the World How: a small group of radar pioneers won
the Second World War and launched a technological revolution
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"The first radar stations used aerials over 100 m in
height to produce a directional beam of radio waves. But if aerials
were much smaller and could be steered, they would be much more
useful. However, to make smaller aerials meant using radio waves
of shorter wavelengths. The cavity magnetron was created to generate
such waves. J T Randall and H A H Boot of the Physics Department,
Birmingham University, made the first cavity magnetron work in
February 1940. Today cavity magnetrons are used in microwave
cookers as well as for detecting radio waves reflected from a
flying aircraft. . . . " More pictures of early radar equipment
here (external link to the Science Museum)
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