I guess this is an antenna topic, as it relates to a 3vmeter installation. Anyway, I was just thinking; Let's say it's the middle of the afternoon and the sky is fully overcast by dark clouds, prime to rain...
Would that provide a pseudo ionosphere kind of effect, potentially create something which part15AM signals could bounce off of?
Might overcast days provide increased range due to the presumably conductive cloud canopy ?
I say no. It's the ionosphere that is involved in the skywave with AM stations at night. Weather has nothing to do with it. We don't have enough power anyways. The ionosphere is way higher than the weather.
When the sun goes down the lower layer of the ionosphere dissipates that usually absorbs radio waves so they bounce off the other layers that reflect it.
That's an interesting question.
My amateur radio background led me to believe that cloud cover (including fog) would affect higher frequencies (VHF & UHF) more, and after some surfing, that does appear to be the case, at least from what I read.
Skywave propagation is from radio waves bouncing off charged particles in the ionosphere. It would be the water droplets, ice, etc. in cloud cover that affects radio signals; AM broadcast band signals have too large a wavelength to be greatly affected. FM signals could either be absorbed or scattered, but in the case of Part 15, that would only occur in fog (the puny FM signal couldn't reach the clouds, unless you're on a mountain).