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Old September 15th 09, 02:15 PM posted to rec.radio.amateur.antenna
christofire christofire is offline
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First recorded activity by RadioBanter: Oct 2008
Posts: 173
Default Spherical radiation pattern


"jaroslav lipka" wrote in message
...
On Sep 15, 7:06 pm, "christofire" wrote:


There is very little apparent similarity between Nicola Tesla and that
'Art
Unwin' character. Tesla was an inventor who realised amazing feats of
hardware construction, some of which worked as intended. 'Professor Unwin'
doesn't appear to create anything in hardware - he just talks about his
own,
paraphysical theories and expects others to believe what he says.

Again, don't believe what I write - go to a technical library and read the
stuff that made it into books. You can't rely on what people write on the
internet; there are too many 'Unwins' out there.

Chris


Hi Chris
The question that goes to nub of Arts claim is
why is adding a time varying field to the Gaussian law of statics
illegal? or to state it another way,
How is it illegal to change a static field into a dynamic field?
can you, will you answer the question or are you just sitting on
Richards shirt tail.

Jaro


I certainly haven't arrived here by sitting on anyone's shirt tails. If
you'd care to read some of the history of this NG you'd see where I come
from.

Your question is not put clearly, although I have seen garbled sentences
like this before in this Usenet group. My first question is: have you
bothered to read any of the respected books on the subject, such as
'Electromagnetics with applications' by Krauss and Fleisch. I suspect if
you had you wouldn't be asking me such a question - it makes no sense! Do I
take it you are referring to Gauss's law for electric fields? Are you aware
that there is a counterpart Gauss's law for magnetic fields? I don't
believe there is such a thing as a single 'Gaussian law of statics' -
someone has made that up!

Gauss's law for electric fields states: the integral of the electric flux
density over a closed surface equals the charge enclosed. This is an
important part of the basis of electrostatics, that is the study of
electrical phenomena caused by static charges, but it applicable at a point
in time to any scenario that involves an enclosed charge - which means any
electrical conductor, whether it carries a non-moving charge, DC or AC.
Gauss's law for magnetic fields states: the integral of the magnetic flux
density over a closed surface is equal to zero, and this is an important
part of the basis of magnetics, again whether static or changing.

Both of Gauss's laws are embodied in Maxwell's equations and for the normal
RF case of sinusoidally-alternating variables a number of different
notations can be used, a popular one being phasor notation. As you will
know, phasors are vectors that rotate at the same angular frequency but have
arbitrary phase relationships and amplitudes - so phasor notation is a
compact way of expressing quite a lot. But, in this case, every one of the
phasors involved, D the displacement current density, rho the enclosed
charge, and B the magnetic flux density, is a variable that alternates with
the passage of time. 'Dynamic' variables if you want to call them that.

Neither of Gauss's laws applies directly to strength of an electric or
magnetic field but the linkage is the other two of Maxwell's equations based
on Ampere's law and Faraday's law, which are both applicable to time-varying
fields - 'dynamic fields' if you must.

So ... would you like to put your question more clearly? What do you
actually mean by 'to change a static field into a dynamic field' in respect
of antennas, where all the electrical and magnetic variables are changing
with time, especially the fields? Is this the result of a misunderstanding
of the meaning of the word 'electrostatic' - used to differentiate between
those phenomena caused by the presence of contained charge and those caused
by its movement?

Chris