I think it has to do with electromagnetic ducting or other clutter effects: http://www.radartutorial.eu/07.waves/wa17.en.html http://www.radartutorial.eu/07.wa

I think it has to do with electromagnetic ducting or other clutter effects: http://www.radartutorial.eu/07.waves/wa17.en.html http://www.radartutorial.eu/07.waves/wa17.en.html If the last effect on the page were in effect, you might get a return, know it's relative bearing well, it's range a little less well, and it's altitude not very well at all.