I occasionally had the same problem. I moved my radios to a high shelf, just below the ceiling. I suspect that might not work for you either. If you don't get a good answer in the next few days I know someone I can ask who is something of an expert on such things but will have to wait a few days to make the call.
I moved my radios to a high shelf, just below the ceiling. <<<
You are right, it won’t work for me.
I will consider any advise that you get.