sci.physics.electromag

"Szczepan Bia³ek" < @ > wrote in message
news:fahk3j$5tb$1@ ...
>
> "Bill Miller"
>>>> "Szczepan Bia³ek" <
>>>>>>>
>>> You often wrote about antenas. What electrons are like in antenas? Water
>>> or gas. (In water only the pressure is changing. in gas also density -
>>> imagine what it means)
>>
>> Actually, in antennas, it seems that electron flow has nothing to do with
>> radiation.
>
> If electron gas is oscillating at the ends of the antena appear
> periodically huge charges. It must something radiate.

Your conclusion would be accurate IF your postulate were correct. However,
in most antennas, the maximum radiation intensity occurs near locations of
maximum current and MINIMUM voltage. In fact, a theoretical dipole has zero
radiation off the ends, and practical dipoles have a ratio of broadside to
end radiation on the order of 20 dB or more..

HOWEVER a friend of mine has built a couple of prototypes of what he has
called a "Teslavert." This type of antenna is basically an externally
driven, HF version of a Tesla Coil, and most of the radiation appears to
come from the ball; not the rest of the structure. I've developed a theory
associated with this. For details, see various articles published on
. The antenna also *appears* to violate (or at least challenge)
the so-called Chu limit.

Before someone challenges ME on that, please accept two points. First, my
friend did not have the time and resources to rigorously test it (and my
prototype is still mostly on paper.) Second, Mother Nature routinely
violates the Chu limit. It's just us dumb humans that don't know how to do
it!

See, for example,

/grimes/publications/ for an example

of a natural "antenna" that is 500 times smaller than conventional
"antennas."

>
>> Instead, the metal seems to "guide" the ready-to-radiate EM energy to
>> where it can do so. An excellent example of this is a microwave "horn"
>> radiator, fed with waveguide. The "horn" can be formed by slowly
>> expanding the dimensions of the waveguide until the Zo of the guide
>> matches that of free space (377 ohm). At that point, the microwave energy
>> radiates from the open end of the waveguide into free space.
>>
>> A similar phenomenon exists in non-radiating structures, but that is the
>> subject of another -- and MUCH longer discussion. This was understood in
>> the 19th century and first (?) espoused by Prof. Poynting in his seminal
>> paper that introduced us to what we now call the Poynting Vector. Please
>> see:
>>
>> /~mcdonald/examples/EM/
>>
>> As Poynting explains, current flow is *always* associated with fields.
>> The same cannot be said for fluids.
>
> I agree that it is the subject of another topic.
> S*

Bill Miller