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Old Feb 21, 2011, 08:46 AM
Totally lost into FPV
Reely's Avatar
Austria
Joined Feb 2011
175 Posts
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Angle to use a patch antenna

Hello.

I would like to buy myself a patch antenna. How can i find out what the angle is that i can use with lets say a 12dbi patch antenna?

I dont have an antenna tracker or a diversity receiver.

Thx, greetings
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Old Feb 21, 2011, 10:06 AM
VaZ
TheFlyer_PT
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Portugal
Joined Feb 2011
611 Posts
I am not sure but I think it should be angled around 45. The best one to answer this question is IBCrazy.
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Old Feb 21, 2011, 10:13 AM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
10,424 Posts
Are you referring to the -3db (half power) angle? If so a 12dbi patch will have a 47 degree window.

Without diversity I would suggest going no higher than 9dbi. As gain increases, it becomes increasingly difficult to stay within the beam unless you are doing target work. I occasionally use a single BiQuad antenna (11dbi) alone when scouting an area far away such as a mountain top, ski resort or construction site from a location a mile or more away. This is what I consider target work. For general flying, go 9db or less.

Perhaps this is a good interpretation:

A 9 dbi antenna has ~70 degree window. So we can assume that within that your range will suffer a maximum of 40% within 35 degrees of center.

Now we go to your 12db antenna. This has a 48 degree window. Thus you now have 40% more range than with the 9 dbi if right out in front. Once you get 26 degrees off center, range is the same between it and the 9db, but deteriorates more rapidly now. Now go to the 35 degrees off center (-3db point of the 9 db antenna). The 9dbi antenna actually has about 50% more range at these edges than the 12dbi.

Thus what I'm saying is that if you have a target you plan to fly over and can aim your antenna at the target, then staying in the window is easy. If you don't have a traget to keep you on track, you'll quickly find you fly out of the beam easily.

-Alex
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Last edited by IBCrazy; Feb 21, 2011 at 10:21 AM.
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Old Feb 21, 2011, 10:41 AM
BEOWULF
North vancouver, B.C. Canada
Joined Apr 2008
18,548 Posts
You are going to have to mount your patch some how, like on a camera tripod as an example.
It is very easy for you to reach over as you fly and adjust your patch as you fly. Once you get the hang of doing this you will understand how simple it is to do.
I forget about low dbi patches now and use rather like 13 or 14 dbi ones with no problem.
don't be scared to touch your patch and manually adjust it as you fly.
Its important to get the correct patch that matches your channel being used.
Quote:
Originally Posted by Reely View Post
Hello.

I would like to buy myself a patch antenna. How can i find out what the angle is that i can use with lets say a 12dbi patch antenna?

I dont have an antenna tracker or a diversity receiver.

Thx, greetings
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Old Feb 21, 2011, 12:59 PM
Totally lost into FPV
Reely's Avatar
Austria
Joined Feb 2011
175 Posts
thx for the great answers.

normaly i fly with a normal 2dbi antenna and i do have a range of 3 km around. the patch i would use on a tripod just for a "longrange" straight flight to one destination and back. for this i would point the patch in that direction and also start and land the plane in this direction.

this should work right? sorry never used a patch before but i think i got the prinzipals

greetz
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