So I've been thinking about trying to build a cellular phone repeater to use inside a home (my girlfriend's basement) because she gets good signal outside, but bad signal inside. I'm thinking its as simple as having a couple good antennas (one for outside, one for inside), band pass filters, and a gain stage or two. The frequencies i need are around 850 Mhz, and possibly the 1900 Mhz range. Has anybody tried this? They sell them for around 500 bucks. I think I have the right idea about this, but am I missing something? Let me know what you guys think.