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Old April 1st 06, 07:21 PM posted to rec.radio.amateur.antenna
K7ITM
 
Posts: n/a
Default Current through coils

Heck, Cecil, I don't see Ian saying that a proper distributed model is
incorrect at all. I see him saying that YOUR model is incorrect! --
For the record, YOU and YOUR below translate to Cecil and Cecil's.

YOUR model doesn't have any capacitance to the outside world, as YOU
have posted and repeated till you are perhaps blue in the face. (No
charge storage translates very directly to no capacitance, in case
anyone could have missed that.)

Because of that YOUR model has, guess what, ZERO time delay along the
coil.

It is ONLY through a combination of both inductance AND capacitance
that you get propagation velocities equal to or less than the speed of
light.

NOTE that in freespace, the speed of light, c, is exactly equal to
1/sqrt(epsilon_naught * mu_naught) -- and the units of epsilon_naught
(freespace permittivity) are FARADS per meter, and mu_naught (freespace
permeability) are HENRIES per meter. A coil increases the henries per
meter, but somehow we seem to have gotten in YOUR model to some space
around the coil in which the permittivity is _zero_ so that we don't
have any capacitance in YOUR model. That would be a good trick, but
it's not one that Ian and I are buying. I suppose that W8JI and Tom D
and Roy and Wes and Reg and Gene and John P and probably the two
Richards and some others are ALSO not buying. Why, even the detailed
Tesla coil calculations I've seen consider the distributed capacitance
to the outside world, in great detail. I'd bet that the authors of
those calculations would ALSO not buy your model.

Putting it another way, propagation of an EM wave requires an
interchange of energy between electric and magnetic fields. With zero
permittivity, there would be no energy stored in the electric field,
and no EM wave. (In a TEM transmission line, it's often said that the
energy is stored in capacitance and inductance along the line, but
that's no different than saying the energy is stored in electric and
magnetic fields.)

It amazes me that you fought so hard for a distributed model in which
that capacitance to the outside world is missing, but insist that the
resulting model allows a non-zero time delay. That's YOUR model; it's
all in the stuff YOU have posted for anyone that wants to go look at
it. By denying the capacitance in the model, YOU are the one who
doesn't accept what's been know since Maxwell and Faraday and Tesla
and...

But YOUR model isn't any use to me, and it seems that it's no use to
Ian. We'd prefer a model that actually accounts for all the currents
correctly, and actually allows for a delay along a transmission-line
structure. Then, knowing it's an ACCURATE model when we can verify
through specific measurements that it agrees to an acceptable level
with those cases we measured, we can look at ways to use that model
as-is, or to use a model which makes life easier for us which matches
the very accurate one closely enough for our purposes.

(Not only does YOUR model with no capacitance to the outside world have
zero propagation delay, but it ALSO leads to a line with infinite
impedance, which I'm ALSO not buying, though with zero delay, the line
impedance really doesn't matter. Also notice that with no capacitance
to the outside world in that area, the model collapses to exactly the
one YOU are arguing AGAINST, except that the straight sections of
antenna are apparently not in the zero-permittivity area, so we need to
keep them separated...it leads to a very strange model, indeed!)

And please note that in the paragraphs above, the only models
specifically mentioned are DISTRIBUTED ones, so don't go giving me any
bull**** about the other kind. And you can save any bull**** about
accepting the fact of capacitance to the outside world, because your
postings repeatedly say otherwise.