It is possible that it is your line of sight to the antenna, I have set up some systems in that general area and KCOS is always a problem, if I am not mistaken, and someone can correct me if I am wrong, I believe the KCOS antenna is the southern most antenna on the mountain, closest to scenic drive. Also check out
www.antennaweb.org, you can input you address and some other information and it can help determine what kind of antenna and which direction to point it in for the best results for each station. Hope this helps.