Yes it certainly can if the antenna is only optimized for the 800 mhz band. As an example, I notice a significant drop in signal for frequencies in the 155 MHZ when I use the Radio Shack 800 MHZ antenna on my Uniden 396T. However, if you are mostly concerned with 800 MHZ frequencies, the Radio Shack 800 MHZ antenna is terrific.
If you need an antenna that covers several bands, you might want to investigate the Austin Condor or other similar antennas. I hope that helps.
If you can spare the time and effort, Have just one 800 MHz scanner ( P25 capable or analogue) with the 800 MHz antenna. Like wise for the Analogue VHF / UHF scanner. I've found monitoring works much better this way.