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> They regained prominence in World War II because of their ability to operate at microwave frequencies I'd always understood the WWII relationship with cats w

• segfaultbuserr 3y ago
  They saw two forms of uses during WW2, both low-tech uses and high-tech uses. Crystal detectors went out of favor soon after vacuum tubes came to prominence, and eventually many researchers almost forgot them entirely due to their outdateness. Later work in microwave electronics made people rediscover their usefulness. Post-war advance in semiconductors made it possible to manufacture small-signal and microwave diodes consistently, finally making them no longer notoriously inconsistent devices. They remain in use for RF/microwave circuit today. Of course, there was also the work by the Indian physicist Jagadish Chandra Bose, an outlier who used crystal detectors to reach millimeter-wave frequency around 60 GHz already in the year 1900 before everyone else. But as far as I can see, his work had limited influence since it was far ahead of his time. In Crystal Fire: The Birth of the Information Age, a definite book on semiconductor history, it described the amazement of this rediscovery: > In the mid-1930s [George] Southworth was trying to detect ultrashort radio waves around a tenth of meter long—what he then dubbed “hyper-frequencies” and are today called microwaves—using specially designed vacuum tubes. But he was having little success. Inherent time lags in the flow of electrons through them were simply too great for the tubes to cope with these extremely short, rapidly oscillating waves. Copper oxide rectifiers didn’t work any better, either. > Frustrated, Southworth decided to try one of the old “cat’s whisker” crystal detectors he had used in radio sets during the Great War, when he served in the Army Signal Corps. These quirky devices had fallen gradually out of favor when vacuum tubes became popular during the 1920s. By the mid-1930s it had become almost impossible to buy one in an ordinary radio store. > So Southworth hopped a train bound for lower Manhattan, where he knew of a secondhand radio market on Cortlandt Alley, near Canal Street. Rummag ing around on the dusty back shelves of one tiny shop, he soon found a few old cat’s-whisker detectors. After bargaining with the shopkeeper, he carried them back to Holmdel, where he dusted them off and carefully inserted one into his receiving apparatus. He began searching around on its surface for a suitable hot spot. Finally, after hunting almost an hour, he found a good one. > And it worked! At last, he could detect his ultrashort-wave, hyper-frequency radiation.
  • alehlopeh 3y ago
    For every scientific achievement, someone in India discovered it decades before.
    • jowdones 3y ago
      >> For every scientific achievement, someone in India discovered it decades before. I have an electronics book from =~ 1950, Romania (still under Soviet occupation at the time). For literally every invention listed there like radio or the vacuum tube, they cite the recognized inventor (Marconi, Lee de Forest) then launch in a visceral diatribe against capitalism and imperialism and state that the thing was first invented by some Russian mujic (peasant), along with it's name, village and picture. But capitalist pigs somehow stole the brilliant but poor guy's invention and pretended it's theirs. So it happens, not just in India. There is an entire retarded cultural movement, I forgot the name, where some God-forgotten tiny place like say "Elbonia" pretends, with evidence, that they invented everything and were everywhere before everyone.
• adrian_b 3y ago
  Nope. Semiconductor diodes were needed for radars, because at such high frequencies the vacuum diodes such as those used in lower frequency radios were inefficient. Because better radars were a priority during WW2, large amounts of money and work were allocated for developing methods for making better semiconductors. The most important place where such research was done were the Bell Laboratories. Before WW2, the available semiconductors were very impure and because of that their true properties were hidden. During WW2 methods to make large quantities of pure germanium and pure silicon have been developed. With the new pure semiconductors, better point-contact semiconductor diodes and better radars were made. The discovery of the bipolar transistor in December 1947 at the Bell Laboratories was just a normal consequence of their work done during WW2, which left them with a much better knowledge about semiconductor properties and with large amounts of pure semiconductors, on which they could do experiments. So like the nuclear energy industry is a product of the WW2 research for making nuclear bombs, the semiconductor industry is a product of the WW2 research for making radars. In both industries, the critical technologies were methods of purification, needed to make enriched uranium and plutonium, and respectively pure germanium and pure silicon.
  • pests 3y ago
    I'm current reading "The Making of the Atomic Bomb" by Richard Rhodes. It's interesting you say that because many scientists they wanted for bomb or nuclear research were sometimes preoccupied with radar. It comes up multiple times in the book. Is there an equivalent book for the work on radar and all the development that went into semiconductors and transistors for radar during the war?
    • timthorn 3y ago
      Check out "The Battle of the Beams" by Tom Whipple, Science Editor of the Times, and whose grandparents were part of the development story. https://www.penguin.co.uk/books/442430/the-battle-of-the-beams-by-whipple-tom/9781787634138 https://www.penguin.co.uk/books/442430/the-battle-of-the-bea...
• deleted 3y ago
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