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Old Mar 05, 2010, 10:57 AM
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Circular polarized antenna question

I'm interested in purchasing a circular polarized patch antenna for my 2.4ghz video system. I see that on nghobbies there are two seperate antennas that are circularly polarized, one which is "left" and the other is "right."

http://www.nghobbies.com/cart/index....roducts_id=164

http://www.nghobbies.com/cart/index....roducts_id=163

Any difference between the two? and is there a higher powered version from any other vendor that might work better?

Thanks.
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Old Mar 05, 2010, 11:43 AM
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Originally Posted by Sov4life View Post
I'm interested in purchasing a circular polarized patch antenna for my 2.4ghz video system. I see that on nghobbies there are two seperate antennas that are circularly polarized, one which is "left" and the other is "right."

http://www.nghobbies.com/cart/index....roducts_id=164

http://www.nghobbies.com/cart/index....roducts_id=163

Any difference between the two? and is there a higher powered version from any other vendor that might work better?

Thanks.
How far do you plan on flying from your GS?
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Old Mar 05, 2010, 11:45 AM
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Well for the first couple months of testing and configuration of my setup, I am looking to go no further than a few hundred feet. Once I get my diversity going I will try to extend that.
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Old Mar 05, 2010, 11:49 AM
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I have been out over 7000 feet with a plan old vertically polarized 8dbi patch antenna. Circular polarization is great if you plan on doing 3D flying over 3000 feet out, but if you are just looking to fly around a mile or more out a Yagi might be what you really want.
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Old Mar 05, 2010, 01:03 PM
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Well the reason that I brought up the idea of using a circular polarized patch antenna was because I have been under the impression that they work better in an area with a lot of trees. Will a standard flat patch antenna work equally as well in a wooded area?
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Old Mar 05, 2010, 01:33 PM
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Will a standard flat patch antenna work equally as well in a wooded area?
Yes, the polarization of the antenna does not have anything to do with the RFs ability to penetrate objects. A circular polarized patch will help you when the plane is banking hard and angles the antenna out of vertical polarization with the GS antenna.
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Old Mar 05, 2010, 03:58 PM
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Tarro, it does actually work better through trees. Only marginally, though.

Long story short, if you only fly around you at less than half a mile, stick to the 3dbi rubber duckies. Up to 3 miles a circular patch is best. Anything above that you'll need diversity with horizontal & vertical polariztion - Yagi or patch won't matter for now, by the time you'll need either you'll be an antenna expert

I can't tell you the difference between left and right polarization, unfortunately. But I can tell you why you need circular:

You have 3dbi loss if you go with a circular at any orientation of your plane. With a vertical polarization you have no loss if you're lined up perfectly, but up to 26dbi loss if your VTx antenna is horizontal and your VRx antenna vertical. So, the circular won't go out as far, but it'll work better when your plane does a hard bank. The other antennas will give you greater range but less "freedom" to move your plane around.
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Old Mar 05, 2010, 04:08 PM
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I can't tell you the difference between left and right polarization, unfortunately. But I can tell you why you need circular:

You have 3dbi loss if you go with a circular at any orientation of your plane. With a vertical polarization you have no loss if you're lined up perfectly, but up to 26dbi loss if your VTx antenna is horizontal and your VRx antenna vertical. So, the circular won't go out as far, but it'll work better when your plane does a hard bank. The other antennas will give you greater range but less "freedom" to move your plane around.
Hey Trappy

You only need to worrie about RH/LH polarization when your doing site to site transmission. RH with RH/LH with LH otherwise from that there is no difference for what were using them for.

Martin
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Last edited by Martin Y; Mar 05, 2010 at 05:06 PM.
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Old Mar 05, 2010, 05:00 PM
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makes sense. thanks martin, one more gap filled
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