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#11
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receive polarity
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 |
#12
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receive polarity
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 |
#13
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receive polarity
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 |
#14
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receive polarity
In message
, Art Unwin writes Has there ever been a study that shows the relative consistency of received signal polarity to see if it would be advantageous for multi polarity receive antennas? When I listen to the local 2m beacon ( horizontal polarisation) which is north of me ,I get a strong reflection from something to the south that turns the polarisation vertical. I noticed that while testing an antenna in the garden. Brian GM4DIJ -- Brian Howie |
#15
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receive polarity
On Feb 15, 6:55*pm, Art Unwin wrote:
I was basing efficiency on all forces being accounted for with a higher gain resulting. Whether or not you account for all forces will not have any effect on gain. :/ This is another case of the hopeful free lunch.. But the cupboard was bare. The radiation from the vertical and horizontal polarizations added together will never end up being more than you started with. And an antenna that is a mix of both will be a compromise if the other antenna is purely one way or the other assuming no reflections, etc skewing the path. No free lunch.. |
#16
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receive polarity
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. |
#17
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receive polarity
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#18
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receive polarity
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 |
#19
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receive polarity
On Feb 21, 11:18*pm, Jeff Liebermann wrote:
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 95060http://802.11junk.com Skype: JeffLiebermann * * AE6KS * *831-336-2558 You have two elements each located with x,y and z co ordinates at each end, so you make your own file to suit the program you intend to use or is available. Surely you can model anything if you know the end locations of the elements. If you are unable to do that then may be it is better that you don't. There are to many programs around for me to make files for every body and every program that is available so I supplied x,y,z co ordinates which every body can translate.These are the points you should look for to determine what the antenna looks like. Either way I have supplied the results to save you the work. |
#20
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receive polarity
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? |
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