I'm pretty sure it involves a DPST switch. I was going to install one myself over the summer, but ran out of time. One of the CEG'rs recommended a push button on the steering wheel column which can raise or lower the antennae manually.
For the life of me, though, I don't know how you would wire it (aside from involving the antennae wire of your system) and how you could run the wiring inside the dash from the head to the steering wheel. Maybe he'll notice this and answer these questions, heh.
