Mobile antenna: I suggest a loaded, gain multiband antenna. Since low band about disappeared in the state,
something that will cover 150 thru 800 mHz. If you are concerned about just 800 mHz, I suggest a ham antenna like the 800 mHz Larsen antenna on a trunk mount or magnetic. Get the one with a coil in the middle of the antenna. I think they are about 25 to 30 inches long.
I am sure that you can find numerous multiband scanner mobile antennas. I used to run a gain antenna that Radio Shack used to make,
and it covered low thru 800 mHz. Since RS is out of business, that unit is probably not available. I remember that Antenna Specialists used to make it, too I'd try e-bay, placing "800 mHz scanner antenna" in for a search. DUKE,WB9OJD
I've never in 42 years of ham radio found a set-mounted antenna to out perform a properly tuned outside antenna.
I have used on-glass antenna on my vehicle (which is a rental), and it works okay for local signals. I put one on my office
window to hear and it works okay too. The outside antenna (before it got water in it and corroded after 20 years), did
work better. As I stated before, I built that one from scratch using #12 wire, PCV pipe, and a length of coax. It wasn't a
perfect match, but I since found a matching network I can incorporate next time I build on. If you are into this seriously,
try building an outside antenna. DUKE, WB9OJD