Shield the coil, the coronas effect is still as powerful on florescents,
vtvms detecting voltage... that voltage may well be inducing a magnetic
field as it is conducted by air/ether/ground... but it looks to me like the
voltage is the main force... rfi will tear up a neighborhood too...

Warmest regards,
John

"Frank" wrote in message
news:GVbje.7002$wr.3522@clgrps12...

"John Smith" wrote in message
...
Ham Op:

Yes, it is... mostly, people who are NOT gifted in explanations that the
"layman" can understand--gravitate to such extreme mathematics (and turn
them off, effectively silencing them).... let me give you my views...

I thought that my explanations were very non-mathematical, requiring only
minimal use of very simple calculations. My response was not complete as
I did not want to go overboard, but try to give very easy examples that
could be expanded on if any interest was shown. Perhaps you could be more
specific as to where I went wrong in my response. My mention of a couple
of textbooks was only to provide references for those interested in trying
to understand concepts in more detail. While it is true that some people
are capable of rigorous mathematical analysis, they cannot explain it in
non-mathematical terms. Those people, then, do not really understand
their subject. It is also true that such complex subjects cannot be fully
understood without in-depth math (Which is something I wish I had).
.
... it is somewhat obvious that when a wave sent forth from our antennas
encounters a metallic object that is close to resonate freq,

Not sure that resonance is important.
and a very good to EXCELLENT conductor, that a LARGE current flows in the
metallic structure encountered--

Current will flow in the surface.

what E and what H wave are then products are debatable (the energy
absorbed is re-radiated)--however--probably of a very different nature
than that of wave which encountered the metallic object in question--and
here is where this debate is ongoing...

If the conducting surface is perfect, no absorbtion takes place. The
reflected EM wave is planar, and identical to the incident plane wave --
with the exception of direction of propagation, and a phase reversal. A
(spatial) standing wave pattern is set up, and the analysis is identical
to that of a shorted transmission line.

at an extreme is a "tesla coil", ultimate voltage and virtually NO
current (very minimal current to generate the nice purple coronas)--yet
an excellent transmitting "antenna"--and that is ALL "E-wave." (well,
mostly...)

A Tesla coil is not an antenna, although some radiation will take place
from its conductors -- which will probably be damped sinusoidal pulses
similar to a spark transmitter. The radiation will not be all "E", but
will have the same E/H ratio of any radiated signal. i.e. E/H = 377
(ohms) in the far field.

73,

Frank


Warmest regards,
John

"Ham op" wrote in message
...
Isn't Kraus "Electromagnetics" a little heavy on the math for the
average Ham ??

Frank wrote:

Hank, and Richard, For a good explanation of this subject I always
liked the book: "Introduction to Electromagnetic Fields" by Paul and
Nasar. The first two chapters of mathematical review are excellent. I
see barnesandnoble.com has the 3rd edition, used, for as low as $66.
John D. Kraus' book; "Electromagnetics" is also a very good text.

73,

Frank

"John Smith" wrote in message
...
Shield the coil, the coronas effect is still as powerful on florescents,
vtvms detecting voltage... that voltage may well be inducing a magnetic
field as it is conducted by air/ether/ground... but it looks to me like
the voltage is the main force... rfi will tear up a neighborhood too...

Warmest regards,
John

Since I have never had experience with a Tesla coil, this is all relatively
new to me. After a little research I found the following information,
which may be of interest.

The Tesla coil design reference at
http://home.wtal.de/herbs_teslapage/design.html provides an Excel spread
sheet showing all the appropriate parameters. The spread sheet example
shows a single gap spark transmitter, of input power 375 W at a frequency of
322 kHz. Since the wavelength is relatively long, at 932 m, the near
field/far field transition is very close to the radiating structure, which
will include the conductive arc plasma.

Near field/far field transition is approximated as (2D^2)/lambda, where D is
the largest dimension of the radiating structure, and lambda is the
wavelength.

The observable effects you mention are therefore most likely due to far
field effects. The E/H ratio is still a constant at 377 ohms. From the
above formula you can see that you would have to be very close to the souce
for any inductive or capacative coupling to occur.

Having heard of Tesla coils I never realized they were only simple spark gap
transmitters.

73,

Frank

First tesla coils I ever made were spark gaps using a 15,000 volt neon sign
transformer, large caps out of aluminum foil, xfrmr oil and polyethylene
sheeting... later on friends and I built units around 50Khz-150Khz which
used push-pull circuits to drive the primary coil of the tesla (no noise
from the spark gap which is almost deafening!)--I think the first used 811
(825's?) tubes from old gov't surplus equip (I remember the tubes were about
the size of coke bottles)....

Warmest regards,
John

"Frank" wrote in message
news:EWkje.7026$wr.338@clgrps12...

"John Smith" wrote in message
...
Shield the coil, the coronas effect is still as powerful on florescents,
vtvms detecting voltage... that voltage may well be inducing a magnetic
field as it is conducted by air/ether/ground... but it looks to me like
the voltage is the main force... rfi will tear up a neighborhood too...

Warmest regards,
John

Since I have never had experience with a Tesla coil, this is all
relatively new to me. After a little research I found the following
information, which may be of interest.

The Tesla coil design reference at
http://home.wtal.de/herbs_teslapage/design.html provides an Excel spread
sheet showing all the appropriate parameters. The spread sheet example
shows a single gap spark transmitter, of input power 375 W at a frequency
of 322 kHz. Since the wavelength is relatively long, at 932 m, the near
field/far field transition is very close to the radiating structure, which
will include the conductive arc plasma.

Near field/far field transition is approximated as (2D^2)/lambda, where D
is the largest dimension of the radiating structure, and lambda is the
wavelength.

The observable effects you mention are therefore most likely due to far
field effects. The E/H ratio is still a constant at 377 ohms. From the
above formula you can see that you would have to be very close to the
souce for any inductive or capacative coupling to occur.

Having heard of Tesla coils I never realized they were only simple spark
gap transmitters.

73,

Frank