I have a 150' tower which has been working fine for 5 years. In the last 2 weeks I have been having problems with the 900 mhz on that tower. The noise floor usually has been in the mid 90's. Now it drops to 50's for a few seconds then returns to mid 80's or higher. Yesterday it worked almost all day fine but today it started up again. I climbed the tower and replaced the 900 radio card and it did not change anything.
I went back up to 60' with a 900 and yagi antenna and never had the floor drop. it was mostly in the 90's to 100 even while the tower dropped.
Any Idea what is going on and how to find and fix it?
Thanks for your input.