Just about any home/base antenna plugged into your scanner/receiver is going to offer you a substantial improvement in reception.
But keep this in mind: the physical size of your Pro 164 presents the designers/manufacturers with big problems when it comes to the most important part of your handset - its front-end and 1st stage filters ......... its a problem all handhelds (and many base) scanner/receivers experience.
While its true the better your antenna the better will be your received signal, the amount of rf then received can be so much (particular in urban areas) that it just saturates your handheld front-end. Net result: very little real-world benefit is actualy realised over time.
Invest in another antenna (a discone or similar? - just about anything is going to be better than the antenna the handset comes with!), but a few coaxial type bandwidth/bandpass filters will go a long way as well to improving things by eliminating a lot of the "rubbish" in the air your receiver would otherwise be having to get rid of before demod.