Here is the situation that is consistantly and repeatedly over looked.
Many question askers that come here to tvfool , refuse to believe that coax and connections and hardware can be bad.
Many question askers will not change out a coax until it is the last possible part of the system to change.
Many question askers will not even install a jumper coax , as a test , to see if coaxes and connection hardware are bad.
Having the DB4e above the roof should be providing strong signals.
As a Test , I recommend connect a New loooong coax to the antenna and run the New loooong coax through a open door or window - direct to 1 Tv.
No splitters , No couplers , No ground blocks , No nothing.
And then try reception.
Then connect the HDP-269 preamp to the New loooong jumper coax.
_____________
Digital Broadcast Tv tuners can develop - Digital Glitches - that are not cleared out with a simple channel scan.
Do a Double Channel scan.
http://www.dtv.gov/rescan.html.