On Feb 15, 6:02*pm, Jeff Liebermann wrote:
On Mon, 15 Feb 2010 08:01:18 -0800 (PST), Art Unwin

wrote:
I have not seen the like printed any where soto me *it is good stuff.

This might offer a clue as to how such antennas are built:
http://ieeexplore.ieee.org/iel3/4812/13333/00608613.pdf?arnumber=608613
http://www.springerlink.com/content/g215405815642611/
Plenty more under IEEE Ants and Props search. *Check if your local
library or college library has a subscription:
http://www.ieeeaps.org
http://ieeeaps.org/aps_trans/

When I model a polarization independent antenna the individual gains
confuse me as each of the individual gains are some what 3 db down
from the "total" gain. In other words "total" is not the addition of
all the polarizations gains.

If you use a circularly polarized antenna, and feed it a linearly
polarized signal (either vertical or horizontal) you'll see a -3dB
polarization mismatch loss.
http://www.antenna-theory.com/basics/antennapol.php

I find it very difficult to get my mind
wrapped around that fact. On the surface it would suggest that
competition types would benefit from a polarization independent
antenna.

Nope. *According to my friends that do contesting, the major
requirement of an antenna is NOT to maximize the gain in all
directions. *It's to reduce the gain to the side and back, where all
the other interfering stations are usually located. *Directionality is
important or all you're going to hear are other local hams. *A truely
isotropic antenna is fairly useless for contesting. *(Note: *I don't
do contesting).

--
Jeff Liebermann * *
150 Felker St #D * *http://www.LearnByDestroying.com
Santa Cruz CA 95060http://802.11junk.com
Skype: JeffLiebermann * * AE6KS * *831-336-2558

To be honest Jeff the antennas I design are based on starting with a
full wavelength radiators which I presume you are already aware of.
Initially I was basing efficiency on all forces being accounted for
with a higher gain resulting. In fact this aproach to design provides
diversity of polarizations instead of linear thus linear seamed to
supply top gains.
The full wave length aproach gives the option of dual polarity or even
all forms.
The penalty is usually in the 1db range where as the multiple polarity
may drop down a bit on gain but makes use of signals that a linear
design cannot hear as well as zero side lobes and good front to rear
figures. So without knowing what polarizations one has to deal with a
reasonable choice is hard to come by. On top of these questions one
has to look t what "gain" really represents since cross polarization
can be reduced to just noise with the rest of the db gain value
representing quality signal. Thus it is difficult to quantify gain
when the real advantage comes about on weak signals that others
cannot hear. In other words gain itself is not important unless it is
a measure of discernabilitity or quality above
noise or none matching polarities.
Two antenna designs come to mind 1 is the two element array that can
supply 2 polarities,
horizontal and one direction circular and 2 the helical that can
accept all that is thrown at it
with a prime gain around 13 db and 10 db for the others. Thus if
polarizations are random
with weather fluctuations in city or wooded area it would seam
reasonable to discard linear forms in favour of helicals. To sum up,
all the above has placed me on a zero level as to what antenna
efficiency really means which to the reader must now be obvious, as
one does not know what variables should be weighted and by how much.,