B
Bernie
Guest
Looking at the pics it's definitely a top loaded antenna, and probably 5/8 wave, which is a pretty good choice for a co-phased array on truck mirrors (dual antennas - see the pics of my GMC in my profile) but a poor choice for this kind of location.
My advice would be to remove it, close up the hole, and get yourself a good quality magnetic mount for the roof. Something like a K40 would be an excellent choice. And, either buy an SWR meter, learn how to use it, and properly tune the antenna, or have it properly tuned at a radio shop.
If you don't want to do that, and want to keep it near the same position, your only good options are a bumper mount (you'll need a different antenna though, and have almost no signal behind you) or a fender mount (requires a hole in the fender and you'll need a different antenna too).
Another option would be to go for a "no ground plane" antenna. These are special antennas used in situations where the mass of the vehicle body doesn't contain enough metal to act as a ground plane, such as with a fiberglass body. That would allow you to keep the same location and still give you a fair signal to the rear and sides, but the metal body of the truck would seriously distort the radiation pattern towards the front. It would have to be very carefully tuned and the pattern checked with a field strength meter.
