I will need to install a GMRS (462-467 MHz) antenna on the rain gutter of an SUV. My primary use will be for vehicle-to-vehicle simplex contacts in often hilly areas. Would I be better off getting an antenna:
1. With a relatively long “no-ground plane required“ antenna or,
2. A shorter 1/4 wave antenna or,
3. Something else?
If you are mounting on the gutter of the vehicle, that's going to put the ground plane (roof) all on one side of the antenna. That'll result in it being directional away from the roof. You'd get better performance by putting the antenna in the center of the roof.
The "no ground plane" antenna will still suffer from the directional pattern. It ~might~ tune up easier, it might not.
Quarter wave antennas are easy and cheap. I'd recommend a 1/4 wave in the center of the roof. If this is temporary/short term, then go with a mag mount. If it's long term, drill the hole.
Hilly terrain isn't going to do you any favors on the GMRS/UHF bands. Increasing antenna gain isn't going to make a whole lot of difference. You could certainly play around with different antenna types and see if one works better.
