Roamio OTA tuners not good?

Are the tuners in the Roamio OTA not very good? I've installed the new TiVo in the same place I had my HDXL. On the HDXL I could consistently receive 6 additional channels that I can't pick up on the Roamio. Also, there are a few channels that I can get on the Roamio, but they sputter even though while watching the signal strength level, it stays pretty constant.

Do I just have a bad unit or have others seen the tuners on the OTA to be somewhat weak?

(#500)