Digital channels 7 and 9 are reception trouble prone VHF high band channels. I recommend a Winegard HD7210P antenna. The HD7210P antenna is a highly directional in the forward direction and rejects signal reflections and interference from other directions other then the front. Try the HD7210P antenna above the roof for reception , position the antenna so has clearest shot past the trees. Also try the antenna down lower to the ground to shoot under the utility wires. And try the reception on the west side of the utility wires both low to the ground and up higher. Put the HD7210P antenna on some antenna mast pipe sections and probe for best reception. Here is how to aim antennas ,
http://www.kyes.com/antenna/pointing/pointing.html Here are some places to buy the HD7210P antenna.
http://www.solidsignal.com ,
http://www.amazon.com ,
http://www.winegarddirect.com.