Hi, I also have an A6, and in the middle of our lawn the squelch only needs
to be on 1. Take it into the house next to the TV / Computer and it
needs 16 on the squelch.

However if I use it on an external aerial, even when next to the TV and
computer, it again only needs squelch 1.

So the answer is simple, just make sure you use an external aerial and good
screened co-ax.

Also check out any BNC Plugs / Connectors. If you can rotate them the
co-ax braid is disconnected and the Plug needs re-doing.... I have found
dozens of loose BNCs in various applications, its the first thing to check.