WW1 "Radar"

Discussion in 'Hangar Flying' started by Aerowerx, Jan 31, 2019.

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  1. Jan 31, 2019 #1

    Aerowerx

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    Aerowerx

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    Well, not exactly radar. Acoustic actually, but quite clever I thought.

    You can see a picture of one here.

    And here is a transcript of the article:



     
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  2. Jan 31, 2019 #2

    lr27

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    At Haystack, a radio telescope facility in Massachusetts, they used to have two old, quite large TV satellite dishes pointing at each other, 100 or more feet apart. You could stand in front of one and have a conversation at normal volume with someone standing in front of the other. That makes me wonder is they really had to make those sound mirrors out of concrete. Maybe there were some wood ones that have now rotted? Or maybe they were for detecting sound at lower than audible frequencies??

    Anyway, thanks for the interesting diversion.
     
  3. Jan 31, 2019 #3

    Aerowerx

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    I would guess that you answered your own question---two different ways.

    Considering the weather in England, particularly the channel coast, wood would probably not last too long. Remember this was WW1 and they didn't have the wood protection techniques we have now.

    Also, with the low drone of the zeppelin engines, the lower pitches would probably carry farther.

    It was also probably easier to smooth the concrete into the right shape than bend a bunch of wood to a precise curve. Just cut a single piece of wood to the right curve and use it as a template on the concrete.

    What I wonder is...Did they have someone sitting there 24/7, or did they have a vacuum tube amplifier and a microphone. This was at the very early days of the vacuum tube and I don't know if they were available yet.

    If I was doing it I would use a telephone microphone at the focus of the parabola and someone sitting inside with headphones (which were available at the time time).
     
  4. Jan 31, 2019 #4

    lr27

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    Somehow I think that if the English could keep some wooden buildings alive for centuries, they could keep a wooden dish thing alive for several years. I would also guess that they could make several wood dishes for the amount of labor, wood, and expense required to make the concrete forms for these things. Maybe they expected the dishes to be bombed? I guess it would take quite a few bombs to completely destroy a concrete one.
    ------------------

    Maybe they could call these things on the phone? I suspect, however, that your idea of having someone right there would be more robust.
     
  5. Jan 31, 2019 #5

    12notes

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    From the BBC article with the pictures: "Interestingly the Kilnsea mirror is one of the only structures to still have the remnants of the metal microphone pole that would have originally been used."
     
  6. Jan 31, 2019 #6

    Aerowerx

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    Remember the Brits don't exactly think the same way we do!;)
     
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  7. Jan 31, 2019 #7

    Pops

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    Thanks , learn something new every day. I love history.
     
  8. Jan 31, 2019 #8

    Highplains

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    If British, they used valves, not tubes.

    The number of zeppelins was limited by the number of cows available for slaughter. The gas bags were made from cow intestines.
     
  9. Jan 31, 2019 #9

    Jerry Lytle

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    There are couple of possible reasons to construct these out of concrete. First they needed to be very resistant to outside vibration either from wind or other local disturbing factors. A second could be the precision of reflector. Possibly a reusable form wood or metal for the reflecting surface. The tolerances could be easily controled by hand placement of the concrete mixture against reflector form.
     
  10. Feb 1, 2019 #10

    pictsidhe

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    Concrete is a much better reflector of sound than wood. A good reflector only needs to be accurate to 1/10 of a wavelength. I don't know the frequency on the Zeppelins, but 100Hz as a total guess would only need a reflector accurate to 13".
     
  11. Feb 1, 2019 #11

    Aesquire

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    Acoustic dishes were used in both sides in Europe in WW2. For early warning & to track raids.

    It's a passive system, you have no way to know if you've been detected.

    The Soviets also had an extensive network of acoustic listening posts in their air defense network.

    The science center in Toronto has reflectors at both ends of it's big "cool science toys" hall, with stairs up to a plastic ring at the focus. Total cacophony of screaming children and equally noisy adults, but you can carry out a quiet conversation with a person at the far end of the hall. Neat!
     
  12. Feb 1, 2019 #12

    BJC

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    The AVG used an acoustic system too; they relied on reports from people hearing approaching Japanese flights.


    BJC

    Edit: Also SOSUS
     
    Last edited: Feb 1, 2019
  13. Feb 1, 2019 #13

    Aerowerx

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    IIRC, the Soviets had a bunch of microphones scattered around Siberia.

    Listening for low flying B-58's I guess.
     
  14. Feb 1, 2019 #14

    lr27

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    Such a system could be quite sophisticated now. I understand that some urban areas have a microphone system which is good enough to locate gunshots. This might be useful against stealthed aircraft as well. In that case, some of the techniques developed for sonar would probably be helpful. Hmm... I could see information derived this way being added to ADSB. Eventually. Maybe tracking flocks of birds, too, keeping airplanes out of the Hudson. I suppose you can find those with radar anyway.
     
  15. Feb 1, 2019 #15

    pictsidhe

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    The urban gunshot system uses triangulation from synced microphones.
     

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