If you build a 1/4 wave vertical GP with down sloped radials, like the old Shooting Star antenna, it will be a better antenna than almost anything else you can do. It will have less common mode, it will be less sensitive to mast or tower size, and it will have as much or more gain along the horizon and useful low angles than any other vertical you could install.
The closest rival is a 1/2 wave with flat radials, but it is more complex and barely any advantage.
A 1/4 GP with downsloped 1/4 wave radials is an almost perfect direct match to 50 ohm cable. The radial angle sets SWR minimum.
All of these supposed broadband CB antennas like the Imax and others are actually single band antennas. I understand people use some of these things on different bands, but some of them work on odd bands because the excite the feedline and supporting mast like a longwire. Some of them work because of losses or because someone just uses a tuner.
Because they "make contact" or "tune with a tuner" does not mean the antenna is multiband.
