mounting a cb antena

bjroadshow wrote:
has anybody mounted a magnetic cb antena to a class A motorhome

If all you want to do is to listen to nearby truckers and occasionally make short-range communications, then as noted a no-ground-plane antenna will work fine. The Firestik is the standard, but there are others: http://www.firestik.com/Catalog/NGP_3-Way.htm.

Otherwise, you'll need a "ground plane." It's kinda complicated, but think of a ground plane as the surface that the radio waves push against to get out of the antenna. It's almost impossible to get a decent ground plane on a vehicle, and contrary to what some people suggest, no, you can't run the coax braid down to the chassis to use it as the ground plane for the radiating element up on the roof. I have seen guys cover the entire roof of the motorhome with diamond plate, but I assume they're either divorced or soon will be. Besides, I doubt it works very well anyway. If you're really interested in antenna theory and how to implement a mobile solution, there's a website (actually geared to hams, but the principles are the same) dedicated solely to that topic. See here: http://www.k0bg.com/.

FWIW, I just installed a NGP antenna and tolerate the inefficient performance.