Reality. Re: Medhurst self resonant frequency and nodality (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

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Date: Thu, 18 Oct 2007 06:59:14 -0400
From: Dave Pierson <davep@xxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Reality.   Re: Medhurst self resonant frequency and nodality (fwd)


>This not only applies to an inductor but to a straight wire as well. In both
>instances the results will be closest to ideal when the solenoid (or wire)
>is long and many nodes are present.
 .....

>The self resonant frequency of Wavelength/2 for a wire is solely a function
>of its length.
  Except.
  The winding of wire into solenoid changes the self resonant frequency.
  cf any good text on antenna engineering.

  Or a good ham radio book, under 'continuosuly loaded antennas'.

  Roughly: for long, skinny, closely wound antennas, ONE HALF wave
  of physical wire length 'looks like' 1/4 wave of straight wire.
  This is the measured reality.
  (To the extent that such arrangements are not commonly used as
   antennas, may need to dig a bit for the refrences.  Still: true.)

  as the 'form factor' changes: becomes shorter/fatter, the physical
  length and the electrical length become closer. 

> Thus a given wire will have the same resonant frequency
>whether it is straight or wound in a solenoid. This stands to reason since
>node spacing is entirely a function of wavelength, or in our case, wire
>length.
   cf as above.

   Try the measurement.

   best
    dwp