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Old Feb 06, 2010, 03:20 PM
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900 mhz Circular aerial

where can I buy a 900mhz circular aerial for my vRX with 8dbi.....I googled but couldnt find anything.
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Old Feb 06, 2010, 04:04 PM
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Circular ? you mean omni ?
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Old Feb 06, 2010, 04:07 PM
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nope, I am looking for the aerial that sends out its signal in a circular (cone) pattern. It was in the video explaining aerials and now dbi effects the waves shape and such. Circular will provide better coverage of when your banking so it helps during the banking turns. Its similar to a patch but its pattern causes it to cover both horizontal and vertical coverage.
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Old Feb 06, 2010, 04:12 PM
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Here we are:
http://fskbt.manufacturer.globalsour...nt-Antenna.htm

But you can as well build a resized GP-patch, it is circular polarised
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Old Feb 06, 2010, 04:21 PM
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Sorry, its for the vRX...so I guess I meant 'receives"
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Old Feb 06, 2010, 04:25 PM
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they dont sell to the public....
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Old Feb 08, 2010, 11:58 AM
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anyone??
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Old Feb 08, 2010, 12:12 PM
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I think the answer is pretty obvious. You can't buy one.
Build a GP Patch.

ian
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Old Feb 08, 2010, 02:50 PM
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that sucks... the benefits it has over a patch are nice. Oh well, patch aerial it is...thanks Ian.
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Old Feb 08, 2010, 03:54 PM
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oops, wrong thread -- sorry
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Old Feb 08, 2010, 05:29 PM
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Quote:
Originally Posted by ATIS View Post
that sucks... the benefits it has over a patch are nice. Oh well, patch aerial it is...thanks Ian.
What exactly do you think the difference between a "circular aerial" and a
"circularly polarized patch" is? If the GP Patch doesn't meet your
criteria then I think you're looking for something that doesn't exist.
Your description above of the benefits though, sounds exactly like that
of a "circularly polarized" antenna which only exist in the form of patches,
or very strange twisted Yagi configurations.

ian
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Old Feb 09, 2010, 08:23 PM
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Ian,

based on the video I thought the following of a "patch":

1) Longer range, but narrower pattern wave lengths shaped either vertically or horizontally depending on how you mounted it.

For the Circular aerial:

1) Longer range but narrow pattern that is spiral/circular in shape allowing better reception during banking when the vTX aeiral isnt veritcal matching the the vRX aerials pattern.

(sorry away on business so finally got on line....can you say 'forum withdrawals"??)
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Old Feb 09, 2010, 09:59 PM
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Need to search for loop yagi
here's a link to a one of 2.4ghz

http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=10127

and one for sale on 900mhz
http://www.directivesystems.com/PDF/3319LYA.PDF

I built this one 15 year's ago for FPV using ham scratch built equipment on 900 mhz. and it worked well but of course with lots of gain you have to point it exactly where you want it. My antenna tracker was built robust enough to swing it around someday. I don't have a clue where the plans are but its on a 8 foot boom and I'm sure if you search ham tv area's you'd find it somewhere.

I dug it out of the garage to take these pictures. My airplane weighed 45 pounds to carry all the junk around. Its easy these days.

Kisssys
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Old Feb 10, 2010, 12:49 AM
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"15 year's ago for FPV " ?
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Old Feb 10, 2010, 02:28 AM
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Quote:
Originally Posted by ATIS View Post
Ian,

based on the video I thought the following of a "patch":

1) Longer range, but narrower pattern wave lengths shaped either vertically or horizontally depending on how you mounted it.

For the Circular aerial:

1) Longer range but narrow pattern that is spiral/circular in shape allowing better reception during banking when the vTX aeiral isnt veritcal matching the the vRX aerials pattern.

(sorry away on business so finally got on line....can you say 'forum withdrawals"??)
A patch antenna can be either linearly polarized or circularly polarized.
Most commercial patches are linearly polarized. The DIY GP Patch is cicularly polarized.
A Yagi can be either linearly polarized or circularly polarized.
Most, if not all commercial Yagis are linearly polarized, but there are DIY designs available for circularly polarized ones.
A whip or dipole is always linearly polarized.

Keep in mind there really aren't many commercial applications outside of the military for tracking moving objects
far away with a high gain antenna. That's why virtually all commercial applications are linearly polarized.
Amateur radio operators have been tracking radios in balloons and satellites for for much longer than FPV
has been around, which is why the circularly polarized antennas are all DIY projects.

ian
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