I had the next to biggest radio shack antenna and the 2 uhf channels I receive were not good at all. So I bought a winegard 7084 hoping to improve the uhf and it did, they are perfect. But the 4 vhf stations are worse. The picture is clear but there are 2 sets of flashing lines across the screen like some kind or interference. I 'm using a channel master 7777 preamp. Can I use a seperate antenna for vhf? Any suggestions would be appreciated.