Ok update time. Tablo = garbage. Expensive garbage. I'm taking it back. I could not get my network to detect it using an ethernet cable OR a wifi connection. In the documentation they talk about a router which I don't have, but I thought I should be able to connect it directly to my ATT gateway. My network did see it, but couldn't connect. Beyond that, apparently, it's very picky about which hard drives it will accept (you need an external hard drive to use it).
So that's out. The FM filter did not seem to have an affect, nor did the attenuator (I used a 2-way splitter, not sure if it was 3.5 dB or not, it didn't say).
I did put my indoor antenna on the patio and holy crap! CBS came in better than ever. So I think you are all right, it's a positioning, and/or antenna thing. The Winegard Flatwave really is a great antenna so I'm going to try to make this work with it. The thing I liked about the Tablo was in theory I could position all of that equipment anywhere, out of site, and stream it to my chromecast, BUT that's out since I can't even connect.
I'm going to either go with a Tivo, or the Channel Master
http://www.channelmaster.com/DVR_Plus_p/cm-7500gb16.htm