Private Lines
About Private Line

Private Line covers what has occurred, is occurring, and will ocurr in telecommunications. Since communication technology constantly changes, you can expect new content posted regularly.

Consider this site an authoritative resource. Its moderators have successful careers in the telecommunications industry. Utilize the content and send comments. As a site about communicating, conversation is encouraged.


Thomas Farely

Tom has produced since 1995. He is now a freelance technology writer who contributes regularly to the site.

His knowledge of telecommunications has served, most notably, the American Heritage Invention and Technology Magazine and The History Channel.
His interview on Alexander Graham Bell will air on the History Channel the end of 2006.

Ken Schmidt

Ken is a licensed attorney who has worked in the tower industry for seven years. He has managed the development of broadcast towers nationwide and developed and built cell towers.

He has been quoted in newspapers and magazines on issues regarding cell towers and has spoke at industry and non-industry conferences on cell tower related issues.

He is recognized as an expert on cell tower leases and due diligence processes for tower acquisitions.

January 15, 2006

Radar: 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, Simon & Schuster (C) 1996 Robert Buderi All rights reserved.


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 be grounded.

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 night.

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 other end.
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 specially reserved?"
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 his leave.

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 defense.

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 mission's secretary.

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 evening.

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' on it."

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 card.

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 use.

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 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. . . ."

Article Index

Recent Posts

Powered by
Movable Type 3.2