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Re: 660/46 Litz Wire Source

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  • bk915
    Thanks John and John. I m wondering whether I even need litz wire. Is one of the reasons for it to increase bandwidth? Also, I think the Q on the antenna I
    Message 1 of 12 , Feb 19, 2013
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      Thanks John and John. I'm wondering whether I even need litz wire. Is one of the reasons for it to increase bandwidth?

      Also, I think the Q on the antenna I just made is too high. It has a very sharp peak that's too narrow to pass the full station passband. I have a pdf regarding this and I can't locate it. I seem to recall that fewer turns results in more gain but less Q, and this is where I read that bit about being too sharp. Although, it said that this would be good for very crowded conditions, which I think might be helpful trying to get something from EU that might be between two stations here.

      Something interesting I'm starting to think about, we picked up this qth a few years ago after someone else had gutted it and done a bunch of work on it. They re-sided it with cast plank siding, but underneath it they put a full sheath of foil covered insulation panels. Reception inside isn't too bad, the antenna does a fine job of nulling out the noise from the pellet stove, but I think I'm going to make my MW listening post on the third floor, which we had finished. The only thing up there is the roofing, with nothing inside except foam insulation and sheetrock. That'll be coming in the next week or so, I guess I'll find out if it makes much difference.

      Thanks again,

      Bill W2NVD



      --- In loopantennas@yahoogroups.com, "thb201" <hudakjm@...> wrote:
      >
      > Litz wire is not just twisted small gauge insulated wire. The gauge of the small strands is sized depending on the frequency range over which it will be used so that most of the wire cross section will carry RF current while minimizing skin effect. For example, for 850kHz. to 1.4MHz., 46 ga. wire is used. For 1kHz. to 10kHz., 30 ga. wire is used. This is because at lower frequencies the skin effect is less and larger sized wire can be used before skin effect starts occurring.
      >
      > When they manufacture Litz wire it is wound in such a way that over any given length of cable, each wire strand will move through each possible position within the wire bundle. This is a much more complicated operation than just twisting the wires. With twisting any given strand will pretty much stay in the same position within the bundle relative to the other strands, while with Litz no two strands will stay near each for any length within the bundle as they are constantly changing position relative to each other.
      >
      > Cheers,
      > John
      >
    • k5gp@sbcglobal.net
      ... I would think a narrow BW means a high Q which means low losses. Would an increased BW indicate higher losses? Are higher losses preferred? 73 de k5gp
      Message 2 of 12 , Feb 19, 2013
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        At 05:19 AM 2/19/2013, you wrote:
        >Thanks John and John. I'm wondering whether I even need litz wire.
        >Is one of the reasons for it to increase bandwidth?
        >
        >Also, I think the Q on the antenna I just made is too high. It has a
        >very sharp peak that's too narrow to pass the full station passband.


        I would think a narrow BW means a high Q which means low
        losses. Would an increased BW indicate higher losses? Are higher
        losses preferred?

        73 de k5gp
      • redsp
        ... If a loop antenna is tuned with a capacitor it forms a tuned circuit. The Q of this circuit is the inductive reactance divided by the resistance. This
        Message 3 of 12 , Feb 19, 2013
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          --- In loopantennas@yahoogroups.com, g.preston@... wrote:
          >
          > At 05:19 AM 2/19/2013, you wrote:
          > >Thanks John and John. I'm wondering whether I even need litz wire.
          > >Is one of the reasons for it to increase bandwidth?
          > >
          > >Also, I think the Q on the antenna I just made is too high. It has a
          > >very sharp peak that's too narrow to pass the full station passband.
          >
          >
          > I would think a narrow BW means a high Q which means low
          > losses. Would an increased BW indicate higher losses? Are higher
          > losses preferred?
          >
          > 73 de k5gp

          If a loop antenna is tuned with a capacitor it forms a tuned circuit. The Q of this circuit is the inductive reactance divided by the resistance. This tells you how large a voltage will form from a constant level of stimulus as the oscillations build up. A higher signal level of course is better at the input of the receiver. But it makes the circuit slower to respond to changes in the level of stimulus. This is manifested as a narrower bandwidth with a higher Q.

          Think of a pendulum swinging. One with a heavier weight is like a circuit with a higher Q. It takes longer to get it swinging and once you stop pushing it, it takes longer to slow down. So it responds more slowly to changes and has a narrower bandwidth.

          The tradeoff is between the signal level and the bandwidth. If you add more resistance to increase the bandwidth, you lower the signal level.

          Rick
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