This may sound silly, but I had a no channel at all problem yesterday. Our gym at work has a TV and an indoor rabbit ear style antenna. Only picks up 4 really bad local channels.
So, I brought in my first home made DB4, which at home pulled in 29 channels and hung it in the window of the gym. Connected it to the TV, ran the scan and nothing, not a single channel.
What the heck, it got 29 at home. Pulled it apart several times, put the old rabbit ears back on got the same bad 4 channels.
Long story short, when I connected the cable to the TV, I bent the center pin over,
, no connection at all = no channels at all. Never occurred to me to look at the end of the cable until I had fooled around with it for an hour.
Take your time and look at all the connections, could be something really simple.