As I mentioned above, my problems come from a cell tower nearby. Once they start getting a lot of traffic, my noise floor drops to -85ish as well, then signal gets really bad.
Keep in mind, at least in the US, licensed frequencies are putting out a lot more power in tighter frequency ranges, just an example, 4w on 2KHz channels, and those signals carry and do cause interference in this band.
I was just about ready to buy a cavity filter, but my test link time is up.
How high is your AP? The higher it is, the more interference you'll see, the more likely you'll need the cavity filter. You need to determine what frequency the noise is coming from. FCC site helped me in that regard.