I have 2 from radio shack, bought them to experiment with and never got around to it. part # 271-1732c. Kieth in Tulsa..........it has 8) so many posts on it I never got around to trying to figure it out.
I have the same one with the same problem. We need either a 1k ohm or 100 ohm control and the one sold from Radio shack is 100k ohm. It's make for much more power. If you're like me, I'm just controlling my xm radio for earbuds. I mounted mine in a project box and stick it with velcro so I can remove it when not using my radio.
FYI, yes that is the one I have, and it did not say what its operational range was and I do not know how to test it. We were all think 8) ing along the same lines though. I use a radio shack in line volume contol if I do not have a mix it 2 amp in the system. the mixit is a bit expensive but it also allows 2 isolated devices to be used with the autocom plus 2 music inputs and it controls the volume from all of them.
Your next step could be to go with a new Active Plus, it has seperate rider and passenger volume controls, as does the new Pro AVI. Both of these new systems also have more input jacks, 3 for the active, 4 for the Pro..............Kieth