In article , -.-. --.- wrote:
Hello ng,

on our ham ng in the it.* hierarchy, a ham posted this PDF:
http://eh-antenna.com/EH_HZ.pdf

I'm not a good mathematic person.. what is written on this PDF goes out of
my analisys possibilities. Perhaps, if gently someone try to explain to me
if there is something of real in what the author claim to be absolutely
real, i'll thank in advance all you readers here.
Just to have a personal opinion about this "Hz field" if someone explain me
in light terms the "physical interpretation" that the author claim in the
paper, based on Maxwell equations.

Here's my understanding, based on what I've read about this general
class of antenna over the past few years.

I'll have to let someone with more math knowledge than I speak about
the specifics of the claims in this paper... it goes beyond what I've
studied. Pretty much everything I've read, says that these claims
depend on a rather different interpretation of Maxwell's equations
than mainstream theory utilizes. The general conclusion I've picked
up, is that you can't generate separate and independent E and H fields
(and then combine them) in the way that EH-antenna theory claims.

As far as I know, well-controlled practical experiments to demonstrate
the benefits of EH-type antennas have not resulted in success. The
antennas "work" to some extent - that is, you can get them to radiate,
and can achieve an impedance match - but the same can be said of
almost any kind of radiating structure. The claims of exceptionally
high electrical efficiency (for such a physically small antenna) don't
seem to work out, though.

In practice (from what I've read), EH antennas seem to behave like
other physically-short dipole antennas which are brought to resonance
by means of a large amount of capacitive end-loading. As such they
have a rather narrow SWR bandwidth, a low radiation resistance, and
the risk of high losses (both in the antenna itself and in the
matching network).

Tests of these sorts of heavily-loaded antennas can be misleading,
unless you take care to decouple the antenna very carefully. If you
just hang an antenna of this sort on a mast and feed it directly with
coax, both the mast structure and the feedline can act as part of the
antenna system, with significant RF currents flowing on them and quite
a bit of RF radiation taking place. This can make the antenna "look
better" than it actually is. Placing the antenna on some sort of
insulated mounting, and using an effective current choke at the
feedpoint, is necessary to distinguish the antenna's own electrical
characteristics from those of the support structure and feedline.

There are some commercial HF antennas which make claims similar to the
EH type - e.g. the Bilal Isotron family. The instructions for some
Isotron models say that they *must* be mounted on a grounded mast for
proper operation... which leads me to believe that radiation from the
mast and feedline are probably an essential part of their operation.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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