David M. Hitchner ...

^ You need to consider that scanners can interact with
^ each other with using a T connector. A scanner will
^ actually generate it's own RF frequencies.

I don't doubt that is true but I haven't experienced it. I generally keep at
least two receivers connected to a single antenna and I've had up to four on
the same antenna. Of the two, one is Sony and the other is RS. The other two
receivers are both RS and they are sometimes on the same antenna too. I have
experienced it though on an RS receiver from a Yaesu radio that's on a
completely separate system, but in close proximity.

Frank