Painted pucks?

The things you think about when you wake up in the middle of the night.

You’ve seen the warning do not paint yet GPS pucks are placed under painted cowls all the time. As long as they are not metal flake I’ve been told. And to boot, the cowl has several layers of fiberglass in addition to paint. Has anyone ever measured performance difference of a puck painted with non metallic paint?

Or is this just the manufacturer’s way of saying we told you so in the event the wrong type of paint was used?

Which leads me to wonder what happens to performance if metal flake was used? It would be an interesting experiment to paint a plastic bowl and cover a puck just to see any changes in reception.

Or is this a bunch of whoey and we except it as fact? Not to mention that cell phone GPS works incredibly well despite bling case covers with metallic foil in purses on the floor of cars while Bluetoothing into the Apple Play.

What say the gallery?

Now time to roll over and grab some more shuteye. Who knows, maybe I dream how to make a bomb release for the pumpkin drop this fall.

On my -4, which is all white, non-metallic paint, I installed my ADSB antenna under the cowl as many have done. The antenna is out of the box Garmin white. My ADS reads are terrible, and spotty at best. What I didn't take into consideration, is my use of aluminized high temp silver primer ( 3-4 coats), I applied on the interior surface of my cowling. It's a paint we use on thrust reverser/cowling components on the B737's ...I'm quite certain this is my problem, and I'm currently moving my antenna to AFT upper fuselage skin inside the canopy. I'm curious if those with metallic paints on their cowlings exterior are getting any degraded signals? I haven't heard of anyone talking about that scenario? Not the same as your question, but similar. At my big jet dayjob, painting an antenna means your replacing it, no fly.

Glas fibre, epoxy or plastics in general is basically transparent for the GPS signals. Metallic paint is not good, carbon fibre and metallic coating (for example on a glass canopy) even worse.

Multi-Band-GNSS systems are better and less prone to errors but when using the stock Garmin GPS, I assume the use quite old tech.

GPS antennas are performing an amazing feat when you think about it, especially considering their minimal size and power requirements. I’m sure some paints & materials are fine, but I can understand why the manufacturers want to keep the variables to an absolute minimum!

To add more mud (flake?) to the waters - a lot of metallics are not actually metal. Mica powder and other non metallic addatives are used, so if some folks report ok under metallic paint, it's probably because it is a non-metal flake.

I've been running 3 GPS pucks under my painted cowl for >2000 hours with excellent signal strength, that's enough evidence for me.
One Dynon, one Avidyne, one Garmin - they all play nice.

Metallic paint does not have metal in it. Mica is the predominate material. Many of these paints have moved to water base. It would corrode.