How to mount GPS antenna to fiberglass canopy?
 

Hey all,

I'm currently researching how exactly to mount my Dynon and Garmin WAAS GPS antennae to the cabin top underneath the overhead console, and wanted to double check what I'm finding.

The solutions out there seem to be:

1. Industrial strength velcro?? I've found a few references to this. Is this legit?
2. Actually cutting hole in the cabin top and mounting the antennae inside. (I have an overhead console, so I think this is off the table.

Is Velcro really an option? If not, I'm imagining that I'm going to want to glass in pieces of harder fiberglass with nutplates mounted to them.

I'd love some guidance from folks on best practices here. I'm much more comfortable working with fiberglass, but tricks like this, which must be just bread and butter for folks that build whole airplanes out of fabric, are still out of my reach.

Thank you!

I would not trust velcro outside the cabin, and you'd have to make a hole for the cable anyway. Mine are mounted through the fiberglass but I did that before I installed the overhead console. It might be a bit difficult once the console is in place. Is aft of the baggage bulkhead an option for you?

What about the ground plane? Garmin recommends an 18" dia ground plane for their GA 35 WAAS antenna.

I have an older GTN 650 install manual and it only mentions the ground plane for the Com antenna not the GPS GA 35. My 650's GPS antenna and the G3X GPS/XM antenna are both mount externally to the cabin top between the doors even though I have an overhead console; no ground plane under either and they work just fine. Maybe I just got lucky - I don't know.

As an aside, my Number 1 Com antenna is on top of the tailcone just aft of the baggage bulkhead so I extended its ground plane out onto the cabin top using 3 runs of 3/8" wide copper foil that I embedded into the fiberglass.

No - if external use standard mounting screws.

On my RV-10 I mounted the GTN-650 and SkyView GPS antenna on top of the glareshield, one on each side. I added a piece of dark cloth over the GTN-650 antenna to keep the glare off the windshield.

Both antennas worked perfectly in this location.

Carl

Many people report good luck with no ground plane on their GPS antenna. Beats me...

I don't see why Velcro wouldn't work. You could also glue it on with 5 minute epoxy, or other non-metallic glue.
Since you are mounting it inside, I think you can probably even mount it upside down without any issues, but you might want to verify that with the manufacturer.
GPS antennas do not need a ground plane. This is demonstrated by any portable GPS with the antenna sticking out of it or on a suction cup on the window.
Good luck.

I'm definitely planning on mounting it INSIDE the cabin, hidden by the overhead console. I agree that velcro on the outside wouldn't be ideal :)

I guess if I didn't want to do that, a better idea would be to attach them with screws to the metal plates that screw in to the overhead console. I don't have anything mounted on those right now, and if I wanted to later I could introduce standoffs. Then the GPS antennae don't have to be upside down and I don't have to modify the cabin top at all.

Any thoughts on that approach?

Is your overhead console carbon fibre like those provided by Aerosport? If so, my understanding is that you can use it as the ground plane. I was discussing this with a fellow RV10 builder who is an electrical engineer and he said that although GPS antennas don't really require a ground plane, he mounted his under the canopy on overhead console which being carbon fibre, was conductive.

Tell it to Garmin. The installation instructions for the GDL-82 require a large one under the GA 32 WAAS antenna. It's a matter of signal-to-noise ratio, I think. The bigger the ground plane, the more signal. You handheld devices can get away with lesser signal. From this graph, it looks like you get 5dB of gain with a 70x70 cm ground plane, and 0 dB with a 30x30 cm ground plane. If my math is right, you get 3 times the signal with a large ground plane.