Hi Cliff,
As you say it depends on what you are using the paint on. I have an Ed Fong (TJB-1) contained inside a piece of PVC pipe. It was working great until I painted it with a Rust-Oleum spray to blend in and guess what? It stopped working. When I removed the paint it worked as advertised. The product I used had metal in the paint matrix.
Moral of the story: caveat emptor
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On Jun 19, 2024, at 11:42 AM, Cliff Sojourner K6CLS via <
cls@...> wrote:
I'm going to be a wet blanket here.? There's a lot of superstition and folklore but very few objective measurements about metal in paint being RF effective.
This matters a lot to hobby rocketry, using 434MHz and 915MHz trackers and telemetry, inside painted airframes.
My practical experience is: very little effect of paint.? Experiments include white paint (titanium dioxide), heavy build primer (lots of zinc), black (carbon for color), and lots of combinations in between.? Not much 70cm signal attenuation, nothing really measurable.
We've also done experiments with airframe materials, including cardboard, FR4 fiberglass (similar to the pultruded dowels for hex beams), epoxy and E glass layups, not colored and colored, and carbon fiber layups.? Of those, only real carbon fiber showed any attenuation.
None of the paints or airframe materials showed any DC conductivity (ohms) at all.
Some years ago, a ham 3D printed a small microwave (mm wave actually) dish, and used a special expensive high-metal paint.? That worked, to the limit of the 3D printed shape.? The paint layer was very thin and I'd expect because of surface effect it would not be effective at lower frequencies.
So yeah very special high metal paints can have some RF effect if you go to enough trouble.
Next step:? trying to organize some calibrated test equipment and both an anechoic chamber and outdoor range.
Cliff K6CLS CM87
