Gary,
For what it's worth, take a look at some of the "Comet" mobile 'dual
band' antennas. They advertise as being broadbanded and are to some
extent (how much, I don't know). I've had no reason to try the
'UHFCB' frequencies, but I do know that at least one of 'Comet's dual-
band antennas is fairly broadbanded on 2 meters/150 Mhz. Can't
measure on the UHF portions so can't say one way or the other.
- 'Doc

And also keep in mind that "FWIW" thingy! As in, don't take my word
for it.