I was banging my head against a wall until i tried this:
Unplug t.v. from antenna and any other source (just power). Scan for available channels (should fine 0, but my find some). Once done, attach antenna, scan channels again.
I went from 2 channels to 40. Prior to was only getting channel 7 and 9 (Washington D.C.).
This is with 25' coax cable to homemade dipole antenna (
http://cs.yrex.com/ke3fl/Articles/An...ePorcupine.htm) with antenna inside house (have since moved to attic with same length of coax; no noticeably better reception - original reception was very good).
I hope this helps! Don't give up!
Funny part of all of this, once I got in the attic I found two disconnected dipole antennas (bought, not homemade like mine) that the previous owner had. I should have checked the attic first.