1. Subscribersonhouse
    Fast and Curious
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    06 Jul '09 21:59
    http://www.physorg.com/news166097923.html

    These guys used string theory to solve a problem hanging around for at least 15 years in the field of superconductivity! Great advance.
  2. Germany
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    08 Jul '09 17:44
    Thanks for posting this! I work in the field of superconductivity, so this is relevant for me.
  3. Subscribersonhouse
    Fast and Curious
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    08 Jul '09 22:05
    Originally posted by KazetNagorra
    Thanks for posting this! I work in the field of superconductivity, so this is relevant for me.
    I am waiting to see if this work leads to improved performance. If so, don't you think this would be a validation of string theory? Or would it still come under the heading of lucky guess? BTW, I contacted American Superconductor Co. and asked if they could sell me some superconductor wire, I have a project where I envision using superconductor wires surrounded by something like polyflow tubing with insulation (not sure of exact kind, but something that could take LN2 temps, and testing its properties as a dipole antenna. I am thinking it would lead to a very hi Q antenna that would cut down out of band noise and thereby raise the S/N ratio of a receiver, therefore lower the power requirements of transmitters, say two sets using identical superconducting antenna's would result in a much lower power requirement for both end transmitters for the same received S/N ratio. At least that's what it seems to me. I explained my project to them and they turned me down. Are these companies still as snooty about whom they sell wire to? If so, do you know where I could get some to try my experiments? I am a ham, my call is AI3N and I would really like to get a project like this going but without access to superconductive wire, am left out in the cold, so to speak🙂
  4. Germany
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    09 Jul '09 18:011 edit
    Originally posted by sonhouse
    I am waiting to see if this work leads to improved performance. If so, don't you think this would be a validation of string theory? Or would it still come under the heading of lucky guess? BTW, I contacted American Superconductor Co. and asked if they could sell me some superconductor wire, I have a project where I envision using superconductor wires surrou this going but without access to superconductive wire, am left out in the cold, so to speak🙂
    No idea, I'm a theorist, and an undergraduate at that.
  5. Subscribersonhouse
    Fast and Curious
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    09 Jul '09 21:26
    Originally posted by KazetNagorra
    [b]No idea, I'm a theorist, and an undergraduate at that.[/b
    So do you know yet how to calc the Q of a superconducting dipole antenna?
    A dipole antenna is a half-wavelength long, so at 40 meters, one of our hambands, you divide the frequency, 40 meters~=7 Mhz, so to find the length of the dipole, which is two equal length 1/4 wavelength sections stretched out with the feedline in the center, so divide the magic # (468) by the frequency in Mhz, and you get the length of the dipole, just shy of 67 feet, or a bit over 33 feet for each 1/4 wave sections. Using those #'s, and the antenna wire diameter, I think, the Q can be figured out, that is to say a center frequency of say, exactly 7 Mhz and then the chart of how the response of the antenna drops off when you go to say, 7.1, 7.2, 7.3, 7.4, 7.5 Mhz, etc., so you build up an SWR chart (standing wave ratio) which when matched perfectly, say a feedline impedence of 73 ohms, a typical dipole impedence, and it's matched to a transmitter also at 73 ohms, then the SWR is 1:1 exactly, so 100 watts fed to the antenna means 100 watts leaves the antenna and nothing heads back to the transmitter. If it were say, 36 ohms instead, 100 watts would head out to the antenna but about half of it would shoot right back to the transmitter, causing no end of trouble there, transmitters like to be one way🙂, they don't like reflected energy zapping them. However, if a transmitter was nearby, transmitting on say, 7.1 Mhz, it would pile up a lot of energy into a receiver tuned to 7.0 Mhz, which would ordinarily be rejected by a series of filters either analog or digital in nature. That works ok, but if the antenna itself can reject frequencies near the operating frequency, the resulting signal to noise ratio will be better, less noise, more signal because off frequency signals will be rejected by the antenna before the operating frequency ever reaches the receiver, see what I mean? That's why I want to explore the Q of a superconductor antenna. Any Idea of how to go about doing the math for this? If you use the standard math, the Q would be infinite, which wouldn't be happening in THIS universe🙂, if that were really true, it would be good for say, 7,000,000.000 Hertz but not good for 7,000,000.001 Hertz! That would be such a narrow bandwidth as to be useless for vocal communications which takes at least 2,000 Hz of analog bandwidth to transmit. So the Q # is a very important value to consider. Any help with that would be appreciated.
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