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Re: Speaking of resonance...
>
> > ...Besides the thing burning up from resistance? Will an extremely long,
> > thin coil wound with thick wire have the same properties of an equally
> > inductive very short coil of large area and high N^2/l ratio?
>
> At low frequency, not, but coils are actually a kind of transmission
> line,
> and the high-frequency effects that come from this depend on the aspect
> ratio, and on how is the coil mounted relative to the ground. For a
> vertically mounted coil with the lower end grounded, the first effect
> that appears is equivalent to a grounded capacitance in parallel with
> the
> coil, given by (units in meters) (Medhurst):
> C= 11.6*length+16*radius+76.4*(radius^3/length)^0.5 picofarads
>
> There are other effects of smaller importance, as additional resonance
> modes and irradiation, that vary with the aspect ratio and position too.
I would like to add my comment here, purely for information sharing. You
cannot use simple transmission line model to work out the resonant frequency
of a coil. The free-space wavelength calculation based on a simple
transmission line model is mainly intended for a straight uncoupled line.
A multi-turned coil should be analysed using the transmission line coupling
model, if you choose to analyse a coil for HF application, (ie. freq. >
500 Mega Hertz).
You will find that all the ordinary transformer coils will not end up with
one
"high quality" resonance when working at a frequency higher than this range
---
mainly because of its standing wave effect and directional coupling effect.
If i understand correctly, Tesla had proposed a very clever approach in one
of
his patent --- apparently similar to what you mentioned, plus making two
transmission planes orthogonal to each other to minimize the their
directional
coupling effects.