steveeh131047 wrote:


Tom,

Yes I have EZNEC and recognise what a great tool it is. Its
predictions were the benchmark against which I tested the various coil
models I read about, and no-one has yet suggested that it can't be
trusted for modelling a helix.

I'm not on some "philosophical quest" - I'm just an old, retired, guy
who still likes learning and wants to understand more about how things
work; I hope that never leaves me! I stumbled on this discussion quite
by chance and tried to understand the various "positions" being taken.
Perhaps I'm over-simplifying, but it seemed to me there was a group
who favoured the transmission-line model and a group against it. I've
tried dispassionately to understand the various arguments and to form
my own conclusions.

Now here's my problem:

* The results I get using a model based on transmission-line analysis
are very close to my EZNEC predictions - not perfect, but way better
than any lumped-element analysis results
* I don't see quantitative, non-empirical, arguments being put forward
to support lumped-element analysis
* I see numeric arguments being put forward by Cecil to support a
transmission-line approach - they look convincing to me and, although
I see a lot of unpleasant personal attacks on him, I don't see any
scientific challenge to his figures
* On the other hand I see folk whose work I rate highly, seemingly
willfully to misunderstand some of the points which Cecil puts forward

Please don't think I'm trying to defend Cecil - I wouldn't be so
presumptuous, and anyway he's old enough to look after himself! I'm
just trying to understand why, what seems to me to be such a
persuasive argument, generates such opposition. Either there's some
glaring technical error here which I haven't yet spotted, or perhaps
there's a long "history" between various "personalities" of which I'm
ignorant?

Still confused,

Steve G3TXQ

There aren't many people who would support a lumped-element analysis on
this newsgroup. Most people know the limitations of using network theory
in these circumstances. The technical arguments against Cecil's approach
were offered a long time ago. This latest is just a flareup that will
soon die down. You shouldn't be confused. The transmission line model of
antennas is well accepted and hoary with age, particularly for
bi-conical antennas (see Schelkunoff). There are a couple of other types
of models with equal validity. If you really want to know the physical
score, though, you have to get an electromagnetics text that discusses
the integral equations that govern antenna behavior. Pay particular
attention to the parts that explain why numerical methods like EZNEC
have to be used for solutions rather than the symbolic math most people
would expect and want.

73,
Tom Donaly, KA6RUH