802.11 Cisco --> Canopy 2.4 Interference

Hiya everyone,

I have a quick question, quick because i think i already know the answer. But i figured i would ask anyways.

I just did a tower buildout on a occupied tower. Now like any good wisp that has to share space we did a spectrum analysis on the tower before we started transmitting or adding any equipment.

There was no 900mhz transmissions coming for the tower. And there was one channel (20ish mhz wide) on 2.4Ghz Which after looking at the tower is a Canopy 2.4 AP.

Now my normal deployments are Canopy 900Mhz (3AP’s–> 120Deg Sectors with CMM or syncpipe/syncinjector) And 3 Cisco 2.4 Wireless Bridges with 120 degree sectors.

Well in this case because someone was using 1 channel on 2.4. I decided to Use a single Omni instead of the 3ap cluster.

The 2.4 Canopy was using “Channel 6” 20mhz wide so i put my cisco on ch.11 20mhz wide (Standard 802.11g OFDM) There is plenty of vertical separation between their omni and my omni as to not cause interference. Now they are both on vertical polarity (theirs and mine)

But yet i received a nasty phone call from this other wisp saying i’m interfering with them. So just in case i moved to ch.1 and they still complain.
I guess the key part of their argument is that I have been interfering with them for 4 weeks now. Which is strange because i’ve only had the power meter installed for 2 weeks and my equip about a week and a half.

But to be a good neighbor i have shut down my 2.4 (I just didn’t tell them that I did) To see if they’re just making it up because they can’t deal with competition. Or to see if theres really a problem.

This other Wisp states that they were told in their “canopy training” that canopy 2.4 gear cannot be on the same tower as other 2.4 ghz gear.
Which i think is a load of horsecrap. Considering i’m not tx’ing on their freq.

Now i guess the question is, am i completely wrong? Or should i tell this other wisp where to shove it, and then proceed to take all their customers that are begging to have me provide service to them, because this “wisp” can’t even return a phone call, or tells people “you loose service because your tower sways too much in the breeze” or makes up other cocamamy excuses. You wouldn’t believe the stories the people that i’ve already moved to my 900’s on that tower that left their service have told me.

But i digress. Is there any chance that i’m wrong? or should i tell them where to shove it?

Thanks a bunch in advance everyone


Your Cisco and the Canopy are NOT going to play well on the same tower. I can guarantee your Cisco is interfering with the Canopy - the problem is that the channels are not as clean as you would like to think.

In order to even have a chance you would need to be H-POL on CH11 and he would need to be V-POL on CH1 but I still have my doubts. Your best bet is to go with a Canopy 2.4AP and co-ordinate sync with them.

You were the last on on the tower - you cause interference, you have to fix it.

Thanks jerry, i had no idea that it would be that noisy to a canopy.
I really don’t think switching to canopy 2.4 gear just for one tower would be a good idea. I’ll probably just take the cisco down and put up a mikrotik in the 5ghz band. I just can’t see ordering a whole lot of gear just for a 2.4 deployment.
Especially for a tower that i expect to get 20-30 LOS customers only.

Just a quick question too.

If the interference is the case , wouldn’t you get interference on the client end in every house that has 2.4Ghz? (IE a Router) no matter what frequency that I use?
Also wouldn’t a bandpass filter to limit my OOB emissions on the AP end help with this?



5GHz make sense.

Consumer routers tx power is low (~18dB) and the antenna is 0 to 3dB gain. by the time the signal gets outside the house it’s probably down around -85dB and not a factor. If you were to put the router next to the CPE you would notice the interference.

Filter might do the trick as long as the incumbent is willing to move to the opposite end of the spectrum.

Out of curiousity, do you or the original occupant have a no interference clause in your contract with the site owner?

How established is this WISP?

You have a couple ways you could handle the situation. You could gear up the tower, take over his unhappy customers, wait him out until the location isnt profitable and force him off via contract with the owner. This is a good way to get cables cut. or you could use this as an opportunity to build a good business relationship with a competitor (assuming their friendly, but their dishonesty so far indicates otherwise), let him know the complaints, offer to help him out, offer to take his “problematic customers” off his hands, otherwise big brother him. and in two years, you buy him.

Sorry for the delay in reply.

The current occupant does not have a no-interference clause.
We do for our frequencies.

To update, i did take my 2.4Ghz transmitter down (they still seem to have interference on that band though, hmmm who woulda thought that)

Now the other company is complaining i’m interfering with equipment they don’t even have on the tower.
It’s just becoming a bundle of fun every day.

Oh well I just answer every complaint as it comes in, then send them back proof of what they have and what they don’t.
It’s like dealing with a child.

Anyways thanks everyone for all the help.