The antenna that comes with the scanner is a great compromise with its ability to receive from 25-1300 MHz. If you only want a portion of the spectrum, then I guess you could "upgrade" to an antenna designed for those frequencies.
I run the RS800 portable antenna if only monitoring UHF, otherwise use the stock antenna. However, when at home I connect to my discone or other external antennas. When mobile I have a VHF/UHF mag mount.