Hello the list,
I was re-reading the AMRAD Active Antenna article today and came across
the following:
"LF signals have very long wavelengths:at 136 kHz, 1 wavelength is 7181 feet. At
these wavelengths, the average suburban yard is less than 1/10 wavelength
across, so
an electrostatic field may be used to approximate LF waves. Thus, at LF, those
areas with a zero electrostatic field will also have a zero, or near-zero LF
field
strength. The freely downloadable student version of the QuickField Finite
Element
Analysis program (www .quickfield.com) can be used to plot the electrostatic
field
around a simple house and yard model.13"
There is indeed a free download student version of Quickfield (release date
3 April 2006!)
Quickfield is a powerful finite-element program that can be used for
electrostatics, heat transfer, DC magnetic fields
AND AC Magnetic fields - could be a powerful tool for calculating core loss in
transformers as well.
But the relevance here is that it will calculate self capacitance and
capacitance between conductors (including fringe effects!)
This may be the way to calculate the capacitance between an LF vertical with
top hat and a counterpoise (or ground).
I'm still learning how to use this tool but it apparently has a lot of
applications at LF.
--
73 Warren K2ORS/WD2XGJ
FN42hi
http://www.w4dex.com/wd2xgj.htm
-------------- Original message ----------------------
From: "Bill Ashlock" <[email protected]>
> Warren,
>
> The comment in my previous post related to the 5 page explanation of
> capacity. Any tricks to downloading the 56 page postscript file? I tried it
> and got some pretty scary results. My computer was all messed up for a
> while.
>
> Bill
> ----- Original Message -----
> From: "Warren K2ORS/WD2XGJ" <[email protected]>
> To: <[email protected]>; <[email protected]>
> Cc: "Bill Ashlock" <[email protected]>
> Sent: Tuesday, April 04, 2006 6:00 PM
> Subject: Re: [LW] parallel plane capacity
>
>
> > Dear Bill,
> >
> > You are correct, the capacitance is much larger due to edge effects.
> > "If you look at the plates then the contours of constant potential form
> > ovals around the plates; and the ovals bulge out a bit more on the
> > outsides of the plates than on the insides, telling us that there is
> > slightly more charge on the inner surface of each plate than on the outer
> > surface. Under these conditions, the capacitance is much larger than would
> > be calculated from the ideal parallel-plate formula."
> > See : "Numerical Analysis of Potential and Capacitance"
> > http://www.mtintouch.net/~fme/captance.html
> >
> > You will probably want to download the postscript file linked from that
> > page.
> >
> > 73 & GL
> > Warren
> >
> >
> > --
> > 73 Warren K2ORS/WD2XGJ
> > FN42hi
> > http://www.w4dex.com/wd2xgj.htm
> >
> > -------------- Original message ----------------------
> > From: "Bill Ashlock" <[email protected]>
> >> All,
> >>
> >> Does anyone have a derivation of the capacity between conductive parallel
> >> planes of finite size but spaced at a reasonable distance? The typical
> >> text
> >> book coverage is for parallel planes having a spacing of much less than
> >> the
> >> linear dimensions of the planes and the formula is simply EoA/d.
> >> Apparently
> >> the fringing field at the edges amounts to a large addition capacity ..
> >> maybe 2X for typical Lowfer top hat heights and sizes.
> >>
> >> Thanks for any help on this.
> >>
> >> Bill
> >>
> >>
> >> ________________________________________
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> >
> >
> >
> >
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> >
> >
>
>
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