[timgr]

If you have the same antenna, are you sure it does not include a preamp that requires power? The only reason to send power to an antenna is to power a preamp located close to the antenna. The preamp boosts the signal voltage to overcomes cable losses - it does not improve signal quality. Signal quality depends on the antenna design and antenna placement. A preamp that is not powered acts like an attenuator, not an amplifier, and very much degrades signal quality.

Also, is your TV set to "antenna" and not "cable?" The character of the incoming signal is very different for the two sources, and the TV tuner needs to know what to look for.