First thing I did once I got my bluey...
If you pop open the boot, and remove the carpet where the jack is stored (there's about 2 plugs near the taillights and a further 2 or 3 on the side near the wheel arch), you'll see the black power antenna motor / assembly.
After some fiddling around, you'll find the cable that powers / controls it - just unplug it. I wrapped some electrical tape around it also just in case it gets too close to a bare piece of metal or something like that.
I was actually thinking of putting a switch in mine so I could control it - it it's up all the way, it catches on some ropes under my carport...
Hope this helps!
- Mortz.