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Can radials of home made ground plane be tapered?

 
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rparigoris



Joined: 24 Nov 2009
Posts: 792

PostPosted: Sun Sep 27, 2020 4:34 am    Post subject: Can radials of home made ground plane be tapered? Reply with quote

Hi Group I have a home made ground plane made out of aluminium for a Garmin GA-35 GPS / WAAS antenna. It has 8 radials 1" wide and ~7.75" long. I'm using the ground plane to support the antenna. It will be living under the ceiling of the baggage bay in a Europa. After cutting out the ground plane I find that it's plenty strong enough to support the antenna. Is it OK to taper the radials from 1" at the root to 1/2" at the tip? I could shave off some weight from the existing 8oz. Ron P.

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prestonkavanagh



Joined: 27 Nov 2018
Posts: 16
Location: Tarpon Springs

PostPosted: Sun Sep 27, 2020 7:54 am    Post subject: Re: Can radials of home made ground plane be tapered? Reply with quote

Others will respond on the radio theory aspect. I'll say that 8 oz is a heck of a lot of weight, and you can do better. I believe the Europa has most of the fiberglass work done at the factory, but I'm guessing you have some supplies around. Slice off a thin piece of foam, shape it to fit, inset a washer with ID equal to the antenna mount OD, one layer of BID on each side and you have something stiff, strong and light. Top it with super thin copper sheet (below is the one I like), and get a 2 oz mount and ground plane ready to attach to the airplane.

Or find a friend among the composite builders! Let me know if you are close to Tampa - I can help. PK

https://www.amazon.com/Conductive-Adhesive-Shielding-Electrical-Grounding/dp/B07R8BS843/ref=sr_1_7?dchild=1&keywords=copper+sheet+foil&qid=1601221863&sr=8-7


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rparigoris



Joined: 24 Nov 2009
Posts: 792

PostPosted: Sun Sep 27, 2020 9:15 am    Post subject: Re: Can radials of home made ground plane be tapered? Reply with quote

Hi PK I already had all of my antennas installed and the FAA now requires an ADS-B Out which I need to accommodate. For my situation the most logical position for my Garmin GA-35 antenna is below the ceiling above the baggage area. The ceiling slopes and is in a constant changing 3D equation where to lay up something or attempt to make a metal shelf would be a chore and not look very nice. My 8 radial .063" ground plane is not just a ground plane but the support for the antenna. It needs to support ~12 lbs. The antenna with screws is over 8oz. My Spider / Ninja Shuriken doesn't look too bad, it's honest. I mocked up a shelf and it looks mucked up. I was thinking about doing exactly as you suggest, thin glass, some thin foam and some thin glass and cover with copper foil that I have. The antenna needs to be close to level to the longitudinal axis which will put the front radial about 2" below the ceiling. Thx. for your offer, I'm in NY. Aeroplanes are compromises and I'm happy with Spider / Ninja Shuriken. If I taper the radials I think I can down to 6oz. The ground plane needs to stay below the base of the antenna which if mounting the antenna inside out of the slip stream negates ability to put on ceiling. If I mounted it on top in the slip stream then I could put copper foil inside but I would need to lift the rear of the antenna and build sort of a submarine bias cut conning tower. Ron P.

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user9253



Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

PostPosted: Sun Sep 27, 2020 3:46 pm    Post subject: Re: Can radials of home made ground plane be tapered? Reply with quote

Maybe you should call Garmin to find out if a ground plane is really necessary.
Other GPS antenna installations do not call for a ground plane.
Garmin G3X Support
g3xpert at garmin dot com
eight six six -854-8433 - 7 to 7 Central Time M to F


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PostPosted: Mon Sep 28, 2020 5:37 am    Post subject: Can radials of home made ground plane be tapered? Reply with quote

On Sun, Sep 27, 2020 at 3:53 PM rparigoris <rparigor(at)hotmail.com (rparigor(at)hotmail.com)> wrote:

Quote:
--> AeroElectric-List message posted by: "rparigoris" <rparigor(at)hotmail.com (rparigor(at)hotmail.com)>

Hi Bob

See page 2-5 of GA-35 antenna installation manual: https://static.garmin.com/pumac/190-00848-00_f.pdf See page 6-8 of GDL-82 installation manual: https://static.garmin.com/pumac/190-01810-00_06.pdf

Ron P.

I'd be at least a little suspicious of some tech writer 'boilerplating' installation text from the last install manual he was working on. Smile 

Virus-free. www.avast.com [url=#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2][/url]


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rparigoris



Joined: 24 Nov 2009
Posts: 792

PostPosted: Mon Sep 28, 2020 8:43 am    Post subject: Re: Can radials of home made ground plane be tapered? Reply with quote

Hi Group FWIW I called Garmin and Stein Air and both said to use a ground plane. I also called Vans. On their RV-12 they install the GA-35 on a small bracket FWF. I called them and asked about a ground plane and they said that the lower cowl acts as a ground plane. Here's a post from a guy in the Vans Forum: "I can tell you this...originally I installed mine under the cowl with little to no ground plane. It worked....

Later I installed a bigger ground plane and the signal levels definately increased." It was posted in reply from a 12/30/2012 question in Vans Forum, he doesn't say what model plane he had, precisely what antenna or how large of a ground plane. I have now heard of several Europa's and a Long EZ using the GA-35 without a ground plane with good success. Ron P.


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