Combining antennas (like anyone says) can be tricky. If you live in an area where signals come from several different locations, there's a few options: use A/B switch for multiple antennas, combine antennas into a joiner, & hope it doesn't cause some stations to degrade, or the expensive option is to have a professional install your antennas. A professional installer for specific markets can install multiple antennas with minimal loss. In cases like that, you might have a general antenna in one direction (for the bulk of you stations), while other directions may have channel specific antennas, & any filters to block out the frequencies from the other antennas.
I already tried to combine 2 Winegard HD9032 antennas (1 pointed at Chicago & 1 pointed at South Bend, IN), & I lost several stations. I still plan to try for South Bend stations, but I'll have to look for a different option, including setting up another pole. If I lived in Porter or LaPorte County Indiana, I could easily combine a combo antenna for Chicago, & a UHF only antenna for South Bend with no trouble, because signal strengths are about the same, while in Lake County Indiana, Chicago stations are stronger, while South Bend stations are weaker, but not impossible to get.