Help finding problem

This showed up last week. To layout what we have: 900 MHZ 6 AP cluster, standard textbook install where 906 is north, then 915, 924, etc…
CMM with sync working fine. This tower has been up and running for about 9 months now just fine. Then last week, on 3 APs (one of each frequency), we noticed that SMs are losing registration and going up & down all day. I changed the APs into SMs and turned all but one off at a time and did a spectrum analysis and the problem APs definitely have something blasting on those frequencies so I’m assuming it’s just an interference problem where there is some 900MHz equipment shooting at our tower desensitizing that side of the tower. Does this sound like a correct diagnosis? And if so what is the best way to find out where this is coming from? I’ve tried driving around and doing spectrum analysises but can’t find the source. It’s killing my customers off of those APs. Any suggestions out there?!

That was exactly the way to diagnose interference.

To locate you need to triangulate.

From the tower use a 900SM with a Yagi and sweep until you find the highest level on the offending freq. Mark the direction on a map

Drive in some direction for about 5 miles and repeat marking the direction on a map

Repeat until you start to see where the lines intersect and through a redious waste of a day you should be able to locate the source.

Yeah that’s what I somewhat attempted to do today, it’s just there are a lot of trees and hills in that area so it’s hard to get a reading in some areas. But I guess I’ll just have to try again. Thanks again Jerry.

If you can determine the exact frequency you might be able to call around to city and county offices and see if anyone had turned on anything.

If nothing else you will generate a good list of names and phone numbers and some exposure to the communications folks in the are.

That’s a good idea, I’ll probably give that a try.

Ok, we found it that it is a company in the area running Trango equipment. They have 3 towers around that area that are each running omni’s on 906, 912, and 924. When I do a spectrum analysis on my APs the noise floor gets brought down to around -50 and is obviously de-sensitizing my APs and making my customers lose connection very often. Is there anything that I can do really besides talk with this company and try to get them to switch frequencies? I’m figuring there isn’t but I’m just hoping for a “magical” solution.

Frequency co-ordination - it’s the only way. You are probably hurting them as much as they are hurting you.

Unfortunately that’s what I thought you might say. Thanks again Jerry.