[old_tv_nut]

combining antennas generally works if one or especially both of the following conditions are met:
1) the antennas are strongly directional and aimed in different directions for the different stations (won't happen using small indoor-style antennas)
2) each antenna/amp is followed by bandpass filters for the desired channels

Otherwise, you will get a strange and unknown combined pattern of reception with a possibility of cancellation as well as reinforcement in any given direction.

Some cities with stations concentrated in two areas instead of one have resulted in well known solutions that even have been named after the city, for example , the "Indianapolis rig." Of course, with stations changing frequencies and sometimes even locations for digital broadcast, these rigs have had to be modified.