I will NOT
cut a hole in the exterior
surface of any vehicle I own. It's not worth the aggravation.
I will NOT
use a magnet-mount on any vehicle I own. I will NOT
tolerate what it does to the finish of the vehicle and I DO NOT
want the cable running for any distance across the top of the vehicle.
As you can tell I'm extremely picky about my vehicle. It killed me to install the ham radio and antenna I did put in....and it took me several months before I finally came up with a way to do it so that I could remove everything and not leave a trace behind that there was ever anything there.
Those things being said, here's 2 solutions you may want to look into.....
Since an Envoy has a rear hatch you might want to look into a lip-mount. The majority of lip-mounts are made for trunks but there are hatchback styles as well. They slide over the edge of the hatch/trunk and are held in place with set screws from underneath. There are no holes to drill and the cable is hidden inside the vehicle. As for security I had one on an earlier vehicle I owned and it stayed on the car at all speeds.
Another option is an antenna mount that drills into the door jamb of your hatch. The bracket then angles out to a horizontal pad where your antenna mounts. This is the mount I'm currently using on my 1996 Ford Explorer.
Both of these antenna mounts allow you to take the antenna itself off for carwashes or low garages while leaving the mount in place. Most mounts that allow the antenna to be taken off come with a screw-on cap that protects the antenna mount threads from weather and dirt.
The included link are pictures of the antenna mount on my truck.
http://pg.photos.yahoo.com/ph/jmpwpd29/ ... pg&.src=ph
This antenna is connected to a Kenwood TM-V708A dual-band ham radio. This is essentially two radios in one chassis. I monitor my local 2m/70cm amateur repeaters on one side of the radio and the local railroads on the other side.
By the way...go to a radio shop that specializes in amateur radio. Your local Radio Shack doesn't have squat anymore compared to what a 'real' radio shop will have. Try these links:
I think you'll probably find something there you'll be able to use.
Good luck in whatever you finally decide to go with!