The last test turned out wrong. I did not see changes in the output that matched cloud cover changes in the sky. I did some thinking about it and the best I can come up with is that autocorrelation is the culprit and that perhaps the chirp is correlating with itself to some degree. In a nutshell, I didn’t put enough bandwidth into the linear chirp for its length.
I think I am seeing some reflections, but they are very short range. The range is less than a kilometer. This makes more sense. I was very surprised to have a range out beyond a few miles.
The one thing I cannot figure out is where all the variation was coming from in the output. If the chirp correlated with itself most of that should have been static but there was a lot of variation. This remains unexplained.
My current test is using a much shorter chirp with a very wide bandwidth and I’m getting a really short range. I’m going to see how this turns out over a long period of time.