Terrestrial Digital Broadcasting in Japan

I’m going to post something before the end of the week on my thoughts about the new TV — quick preview: sweeeeeet — but I have a quick question I’m wondering if someone could answer. I have everything hooked up to receive terrestrial digital broadcasting (there’s a plug to my building’s antenna in the wall), and I’m usually getting all the channels, but sometimes some disappear because of low signal. Is there anything I can do to get a stronger UHF signal (something I can buy, as I don’t think anything can be done about the building’s antenna)? I did buy a new BS/CS satellite, and should be getting SkyPerfecTV! 110 from tomorrow or Friday.