I think while Darryl's suggestion will work quite well, it is more
effort than is required.Â* The BNC connector and the nut and washer of a
rod antenna will provide the necessary electrical connection to the
ground plane.Â* With a blade antenna, the mounting studs will make a good
mechanical connection.

In my former LAK-17a, I used an aluminum square cut to the dimensions
specified in the antenna installation sheet and rolled it over an oxygen
tank to match the internal curvature of the fuselage aft of the landing
gear.Â* I glued it in place with contact cement knowing that the studs
and BNC would make a good mechanical and electrical connection.Â* It
worked great!Â* I mounted the antenna offset to one side for two
reasons;Â* first, the joint line of the fuselage halves was thicker than
the length of the studs and BNC, and second, it insured that the blade
antenna would not catch on the ramp when loading and unloading the
fuselage in the trailer.

On 12/28/2019 7:43 PM, Darryl Ramm wrote:
On Saturday, December 28, 2019 at 4:10:30 PM UTC-8, wrote:
"Pay attention to the proper ground plane installation with any of the standard external transponder 1/4 wave antenna. That is very important."
Can the ground Plane be inside a carbon fibre fuselage for an external blade type antenna ?
Dan
The ground plane you install would normally be inside the CF fuselage. And the antenna manufacture or glider manufacturer should provide instructions on how to do this properly. A part of the point of that aluminium plate or foil tape ground plane is to help with a good connection to the coax cable ground. In some cases you might scuff the inside of the fueslage to help make additional electrical connection to the carbon fibre weave. *Follow the directions your glider manufacturer provides.* A plate especially can also help provide a good solid surface for antenna lock washers to engage with. Clearly here the CF will act in part as a ground plane (even without a good direct electrical connection, but by backing it with a better conductor with good connection to the coax you are helping things along).


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Dan, 5J