With a built in amplifier, I suspect the TV24746 was overloading due to the strong local signals, that would be a likely explanation for the 'test' results you got.
If you have a Home Depot nearby, their return policy is very generous. Try a non amplified
http://www.homedepot.com/p/t/2026992...9#.UV9SxRxx3W8... I think the same test will produce different results.
Still, I would just go get a small combo UHF/H-VHF outdoor antenna, no amp and be done.