Help with High VHF

[bikedoc]

I have a Winegard HD 7696P with a winegard AP 8700 Amp on the mast at this location http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d40335f7ae162bb the antenna is 26 feet off the ground and is pointed at 150 degrees magnetic. The UHF channels on my report come in well, but I have intermittant problems with high VHF channels 7 and 11 (virtual 13). I am using RG6 and have a 75 foot run from the AMP to the TV. The problem is worse in the evenings and AM. I have tried my setup both with and without the AMP and have no change. The signal on channel 7 will go from no signal to 90%

[GroundUrMast]

When you look at the path profiles of KGO (http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d40335f7ae162bb%26t%3dALLTV%26n%3d3) and KNTV (http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d40335f7ae162bb%26t%3dALLTV%26n%3d6) (simply click on the call sign listed on your TVFR) you can see that terrain poses some difficulty. Your description and your TVFR both indicate that raw signal strength is not the problem (which is why amplification did not help).

As an experiment, you could try lowering the antenna to within a few feet of the ground, where it still has an unobstructed view of the ridge top south of your location. (The purpose of the experiment is to determine if the signals of these two stations are less affected by multipath close to the ground. You may find you'll have some trouble with one or more UHF signals during the 'experiment'.)

A separate high-VHF antenna or a ganged/stacked array (http://forum.tvfool.com/showthread.php?t=1024) may be worth considering also. I think it's more practical to try adjusting your existing equipment before resorting to the additional expense and complexity though.

[Electron]

Try turning the antenna to the left and right , away from 150 degree magnetic compass. On the roof , move the the antenna up and down and if you safely can walk the roof with the antenna to find a better spot for reception.

[No static at all]

Sounds like it may be an interference issue since the problem is occurring at only certain times. Any electronics or maybe florescent/led lights that are turned on only during these times? If so, you may want to try turning them on then off to test?

A while back I discovered that a certain brand of multimedia speakers I used would wipe out one of my VHF channels when turned on.