On Mon, 15 Feb 2010 14:07:35 -0800 (PST), JIMMIE
wrote:

What is/are "polarizations gains". That's a term with which I am not
familiar.

Hi Jimmie,

EZNEC, for one, reports antenna "gain"/directivity (re dBi) for each
polarization, azimuthum or elevation; or their sum as a total field
for a 3D model.

When two antennas (one receive, one transmit) are cross polarized, the
gain between them can vanish to zero. In a real application this zero
is something larger, but still small like 30dB down compared to two
antennas employing the same polarization.

This last is observed in line of sight transmissions of VHF and above
(try hitting your favorite 2M repeater with the wrong antenna
polarization orientation). It is not so common at HF as long paths
(aka skip) can blur the polarization (as can nearby reflectors for any
frequency) causing intermittant fading.

73's
Richard Clark, KB7QHC

On Feb 15, 6:38*pm, Richard Clark wrote:
On Mon, 15 Feb 2010 14:07:35 -0800 (PST), JIMMIE

wrote:
What is/are "polarizations gains". That's a term with *which *I am not
familiar.

Hi Jimmie,

EZNEC, for one, reports antenna "gain"/directivity (re dBi) for each
polarization, azimuthum or elevation; or their sum as a total field
for a 3D model.

When two antennas (one receive, one transmit) are cross polarized, the
gain between them can vanish to zero. *In a real application this zero
is something larger, but still small like 30dB down compared to two
antennas employing the same polarization.

This last is observed in line of sight transmissions of VHF and above
(try hitting your favorite 2M repeater with the wrong antenna
polarization orientation). *It is not so common at HF as long paths
(aka skip) can blur the polarization (as can nearby reflectors for any
frequency) causing intermittant fading.

73's
Richard Clark, KB7QHC

A different perspective on polarization loss?

Jimmie

On Mon, 15 Feb 2010 19:04:51 -0800 (PST), JIMMIE
wrote:

A different perspective on polarization loss?

Different? How? All pretty standard stuff.

As for different literal perspectives of polarization, I am sitting
here with two sets of 3D glasses for "Avatar" (just got back from the
IMAX version) and these two pair of glasses are very different from my
experience with Polaroid lenses of days gone by. And they are very
different from each other for the same movie.

The Real3D glasses at IMAX didn't work as normally worn, I still saw a
double image; but viewing the movie through the lenses backwards (ear
pieces going forward) rendered the IMAX 3D as 2D.

Now, when I sit here at the console and view the display (flat screen)
through the IMAX lenses, I can dim the display by rotating the pair.
One eye piece goes black at 45 degrees rotation, and the other eye
piece goes black at -45 degrees rotation. Flip them to look through
them backwards, and the same effect is observed.

When I take the Real3D pair and rotate them, only a slight shift in
hue: yellow tint in both lenses at 45 degrees rotation, and a blue
tint at -45 degrees rotation. When I flip them to look through them
backwards, I encounter a slight brightening for both lenses at 45
degrees rotation and a complete blocking for both lenses at -45
degrees.

I am familiar with display technology employing LCDs with double
polarization to increase contrast, and I could easily expect this from
the lenses of these two pairs of 3D glasses. Without having gone
further into researching it, I have a hunch that I am encountering
circular polarization here.

A little digging will tell.

73's
Richard Clark, KB7QHC

On Mon, 15 Feb 2010 22:44:13 -0800, Richard Clark
wrote:

Without having gone
further into researching it, I have a hunch that I am encountering
circular polarization here.

Yep. RealD XL 3D is circularly polarized:
http://en.wikipedia.org/wiki/RealD_Cinema
http://en.wikipedia.org/wiki/List_of_RealD_films

"How to avoid getting a 3D headache while watching Avatar"
http://www.shadowlocked.com/index.php?option=com_content&view=article&id=70:ho w-to-avoid-getting-a-3d-headache-while-watching-avatar&catid=41:feature




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

Jeff Liebermann wrote:
On Mon, 15 Feb 2010 22:44:13 -0800, Richard Clark
wrote:

Without having gone
further into researching it, I have a hunch that I am encountering
circular polarization here.

Yep. RealD XL 3D is circularly polarized:
http://en.wikipedia.org/wiki/RealD_Cinema
http://en.wikipedia.org/wiki/List_of_RealD_films

"How to avoid getting a 3D headache while watching Avatar"
http://www.shadowlocked.com/index.php?option=com_content&view=article&id=70:ho w-to-avoid-getting-a-3d-headache-while-watching-avatar&catid=41:feature





Which makes perfect sense, since it means that if you tilt your head,
you don't swap images between left and right eyes. A very clever use of CP.

Model of 2 element multi polarization.

http://users.sdsc.edu/~unwin/art/Picture6.png
http://users.sdsc.edu/~unwin/art/Picture7.png
http://users.sdsc.edu/~unwin/art/Picture10.png
http://users.sdsc.edu/~unwin/art/Picture11.png

On Sun, 21 Feb 2010 19:45:03 -0800 (PST), Art Unwin
wrote:

Model of 2 element multi polarization.
http://users.sdsc.edu/~unwin/art/Picture6.png
http://users.sdsc.edu/~unwin/art/Picture7.png
http://users.sdsc.edu/~unwin/art/Picture10.png
http://users.sdsc.edu/~unwin/art/Picture11.png

I don't see a model. There is no .EZ, .GAA, .N4W or .NEC file for me
to play with and tear apart. I can't even tell what the antenna looks
like from what you've posted.

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

On Feb 22, 3:45*am, Art Unwin wrote:
Model of 2 element multi polarization.

http://users.sdsc.edu/~unwin/art/Pic.../Picture11.png


and this proves what?