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Re: [loopantennas] fs loop article

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  • everettsharp@aol.com
    John, Litz wire reduces the impact of the skin effect and the proximity effect. So for a piratical explanation I have just wound a 18 turn coil with standard
    Message 1 of 38 , Jan 6, 2013
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      John,
       
      Litz wire reduces the impact of the skin effect and the proximity effect. So for a piratical explanation I have just wound a 18 turn coil with standard solid 18 gage wire, close wound, on a 7.5" FSL and I find the tuning range (using a 10 to 381 pf variable capacitor) is 1200 to 400 KHz. Now I rewind a 18 turn coil, close wound, on the same 7.5" FSL using 660/46 Litz wire, and I now find the tuning range is 1850 to 405 KHz. So my question to you is if it is not higher distributed capacitance using the solid wire over that of the Litz wire, then what is it that is causing the frequency, at the high end of the band to be lower and having less tuning range? This is not theory, this is what I see from a piratical stand point. I am sure that if you want the theory behind it you can find it somewhere here on the web. (I am not skeptical, I am a believer) 
       
      Everett
       
       
       
       
       
      In a message dated 1/5/2013 11:25:00 P.M. Central Standard Time, jpopelish@... writes:
       

      On 01/05/2013 09:15 PM, everettsharp@... wrote:
      > Hi John,
      >
      > It probably does not mean anything if you have enough space between the
      > turns, but when you have the windings next to each other, then distributed
      > capacitance does become a major factor. Blitz wire does have less distributed
      > capacitance when the windings are butted up next to each other, then does
      > standard wire.

      I didn't know that. Is this a fact you have measured, or a
      claim you have read, somewhere? (I'm sceptical.)

      --
      Regards,

      John Popelish

    • John Popelish
      ... (snip) ... Here is what I am thinking about, with regard to comparing Litz to solid (or any other two choices of winding conductor. As long as the resonant
      Message 38 of 38 , Jan 10, 2013
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        On 01/06/2013 01:08 PM, everettsharp@... wrote:
        > jpopelish@... writes:
        >> (mailto:everettsharp@...) wrote:

        >>> Litz wire reduces the impact of the skin effect and
        >>> the proximity effect. So for a piratical explanation
        >>> I have just wound a 18 turn coil with standard solid
        >>> 18 gage wire, close wound, on a 7.5" FSL and I find
        >>> the tuning range (using a 10 to 381 pf variable
        >>> capacitor) is 1200 to 400 KHz. Now I rewind a 18 turn
        >>> coil, close wound, on the same 7.5" FSL using 660/46
        >>> Litz wire, and I now find the tuning range is 1850
        >>> to 405 KHz. So my question to you is if it is not
        >>> higher distributed capacitance using the solid wire
        >>> over that of the Litz wire, then what is it that is
        >>> causing the frequency, at the high end of the band
        >>> to be lower and having less tuning range? This is
        >>> not theory, this is what I see from a piratical stand
        >>> point. I am sure that if you want the theory behind
        >>> it you can find it somewhere here on the web. (I am
        >>> not skeptical, I am a believer)
        (snip)
        >
        >> One more question. Was the length (across the turns)
        >> of the 18 turn Litz coil the same as the length of the
        >> 18 turn solid wire coil? In other words, was the 18
        >> gauge solid wire the same width as the (as wound) Litz
        >> wire?


        > I don't know what the length was of the two wires, as I
        > did not measure them. However, the cross section area
        > of 660/46 Litz wire is nearly the same as solid 18 gage
        > wire.

        Here is what I am thinking about, with regard to comparing
        Litz to solid (or any other two choices of winding conductor.

        As long as the resonant Q of a the inductance of a loop and
        with its own stray capacitance and a tuning capacitor allows
        some actual math solutions, if two tuning cap values and two
        resonant frequencies are available from an experiment, it
        should be possible to calculate the actual coil inductance
        and effective, parallel, stray capacitance. The additional
        requirement is that, either the resonant Q is about 10 or
        higher, so the losses do not appreciably affect the resonant
        frequencies, or the effective losses must be calculable for
        the for the loop at the two resonant frequencies.

        The point being, that with a given coil, and two resonant
        frequencies, with two values of tuning capacitance, it
        should be possible to calculate the loop inductance and loop
        stray capacitance, by solving a pair of simultaneous
        equations for each coil.

        So, it should be possible with these two resonant
        frequencies, per coil, with two values of tuning
        capacitance, we should be able actually solve for any coil's
        actual inductance and stray capacitance.

        This technique should be handy to compare any two different
        construction choices (diameter, turn spacing, conductor
        strands, wire insulation, form material, etc.) to work
        toward an optimum (widest tuning range per dollar, highest Q
        per dollar, or whatever figure of merit you choose) design
        for any available coil conductor material and construction
        technique.

        This solution rapidly takes coil design optimization out of
        the opinion phase and moves it into experimental science.

        --
        Regards,

        John Popelish
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