NEC-LIST: Re: [Antenna Discussion] RE: Radiation From Antennas

Kirk,
   Adding my 2 cents worth of knowledge, your explanation is very
interesting and represent s a very valid modern Quantum point of view. It
is interesting to contrast it with an old fashion conventional electron/wave
approach which states that the radiation from a quarter wave monopole is
about 40% at the top, about 40% at the base, and 20% spread over the rest of
the monopole. This was based on a significant mathematical analysis by
Schekunoff and Feldman (Proceeding of the IRE, November 1942, page 511 to
516). The concept on which it based is that radiation occurrs only during
electron accaleration or deacceleration.

 Once we start with photons other doors open up. Where will it end. Maybe
antennas which are not tied to wavelenghts. After all, we have miniaturized
all electron devics. Maybe now is the time for all of us to team up and
miniaturize the antennas.
            Regards, Joe Jahoda jjahoda_at_astronwireless.com
                                                         jsjahoda_at_aol.com

"Jack L. Stone" <jack_at_antennex.com> writes:
> Kirk: I'm extrememly glad this thread was started as it brings us right
back
> to a VERY basic element of the antenna dynamics. From all of the wide and
> varied definitions of first, the Photon itself and second, how it behaves
as
> it does within the antenna, there remains a lot of answers yet to find.
>
> This very basic factor which should be encouraging for those involvled in
> experiments. Then is it proper to say, since our scientific understanding
is
> blurred at best about the basic behavior of photons on an antenna in
> production of signals that shoot/leap/fall from the antenna, then we have
> many, many more *types* of radiators yet to explore--??
>
> -----Original Message-----
> From: Kirk T McDonald [mailto:kirkmcd_at_Princeton.EDU]
> Sent: Wednesday, October 29, 2003 12:43 PM
> To: ghagn_at_erols.com
> Cc: Jack Stone
> Subject: Re: [Antenna Discussion] RE: Radiation From Antennas
>
>
> George,
>
> A photon, like all other quantum mechanical objects, is not as
"localizable"
> as a "classical" description could imagine.
>
> Therefore, a question like "exactly where on an antenna (a dipole, for
> example) does the radiation actually come from?" does not have an "exact"
> answer.
>
> A photon cannot, in general, be localized to distances smaller than its
> wavelength.
>
> Most antennas are smaller than the wavelength of their radiation.
>
> Hence, the photons do not come from any particular point on the antenna.
> The entire antenna participates in the generation of the photons. The
> buzzword for this is "coherent" production of the photons.
>
> ...................
>
> Some factoids about linear dipole antennas whose length L is much less
than
> the wavelength of the radiation.
>
> In this case, the charge distribution whose acceleration creates the
> radiation is UNIFORM along the length of the antenna (but oscillating in
> time), except that it has one sign on one arm of the antenna, and the
other
> sign on the other arm.
>
> Since the radiating charge distribution is uniform, even classically, we
are
> hard put to identify a "point" where the radiation occurs.
>
> In particular, the "tips" of the dipole antenna do NOT play any special
role
> (other than indicating the spatial boundary of the uniform charge
> distribution).
>
> Remember that no dipole radiation is emitted along the direction of the
arms
> of the dipole; the peak strength of the radiation is perpendicular to the
> direction of the arms. One should NOT think of the radiation as due to
some
> kind of action that flows down the arms of the dipoles, which abruptly
halts
> at the ends of those arms, resulting in radiation the "leaps" off the ends
.
>
> In fact, the current that is fed into the arms (from the feed at the
center
> of the antenna) decreases smoothly from full strength at the center of the
> antenna to zero current at the "tips". There is nothing about this
behavior
> that "localizes" the origin of the radiation.
>
> Bottom line: the entire antenna participates in the radiation => can't say
> exactly where the photons (which are bigger than the antenna!)
> are created.
>
> --Kirk McDonald
>
> ----- Original Message -----
> From: <ghagn_at_erols.com>
> To: <jack_at_antennex.com>; <antenna-discussion_at_antennex.com>
> Cc: <ghagn_at_erols.com>
> Sent: Monday, October 27, 2003 2:40 PM
> Subject: [Antenna Discussion] RE: Radiation From Antennas
>
>
> > Jack:
> >
> > Be careful, as you are getting off into "photon Zen," or some other
> > philosophical space.
> >
> > An equally intersting question that does not depend on the possible
> motives
> > of a photon is exactly where on an antenna (a dipole, for example) does
> the
> > radiation actually come from.
> >
> > We know that a moving charge radiates when it accelerates or
decelerates.
> > We know that the charge decelerates at the ends of the dipole, because
it
> > runs out of wire! That is what motivates the electron to stop at the end
> of
> > the wire. It would literally be a leap of faith for the electron to
> proceed
> > on off the wire into "free space." We also know that the current changes
> > direction (by 90 degrees) when it goes from a vertically-hanging
> > transmission line to a horizontally oriented dipole. Since a change of
> > direction can also cause radiation, there must be some radiation from
near
> > the feed. The motivation for the electron to go on around the corner is
> > that is where the conductor goes, and charge cannot "pile up." But the
> > heavy lifting regarding radiation is done from near the ends of the
> dipole.
> > Or so it seems to me.
> >
> > Any comments?
> >
> > George
>
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