Can someone explain how?
 

Friend bought a house with a roof mounted antenna. Hook up the tv and got thirteen channels. Come back later on the same day, changed nothing and had 8 channels. Later that night he calls me to say he has NO channels. Again, nothing changed including weather. Next day he has 5, then none, etc. New amplifier on antenna, good CM antenna, directed off a compass. What are we missing?

Are you in Northeast, PA, a town near Erie, PA or in North East PA
near Scranton, Wilkes-Barre????
Need a whole lot more information from you....
Distance to transmitters, elevation, trees, etc, etc, etc

In the Williamsport area. Here is my tvfool report.

http://www.tvfool.com/?option=com_wr...9038c3e55bbc79

House is high atop a mountain. Neighbors can get 11 and 13 from a simple antenna in their first floor living room. He can't get either.

According to the report, Harrisburg should provide the strongest
signals, yet Rf 11 and Rf 13 are from the Scranton market.
Are there nearby trees? How close are they and how tall?
Buildings?
The fact that reception is so variable, tells me there is most
likely something wrong with the antenna system.

I was thinking that also. There is nothing blocking the view that I can tell. I am going to replace all the coax and balums and see what happens.