3.65 Channels

What is everyone using for 3.65 channels?

Currently we are using 3 x 10MHz




Is anybody using 5 x 10MHz channels or 3 x 20MHz ?

Are you talking about using GPS sync/frequency reuse? We have one site that we use 4x20 and 1x10 and it works pretty well... there's a lot of physical seperation between the antennas though.

Hi Logonix,

Please  let us know if you are referring to the the number of channels that you can use in 3.65 band. Also are you facing issue with the transmit getting disabled. Kindly elaborate the issue in order to assist you further.


Vivek Gupta

I set up out custom frequencies to use every 0.5 MHz from 3652.5 to 3697.5, just in case we need that kind of detail down the road, though we only enable every 2.5 MHz in the SMs to speed up registration time.

We're using 10 MHz channels with one exception that is 5 MHz to fit into the only gap in the noise in that direction.

Because of the amount of Ubiquiti 3.65 noise in our area, every AP has to be configured to work around it.  The sector spectrum analysis feature is fantastic for finding the gaps by comparing the AP and remote SM spectrums.


I am referring to channel use on a single tower.  What Cambium often describes as ABAB.  We are currently using 10MHz channels with only 3 possible channel options using a 10MHz wide guard band. 

Things work great on the one tower, but we are seeing issues when using the same channel in RF range on another tower.   With PMP100 900MHz, I was able to use H vs V polarity to  help resolve issue.  However, 365 is MIMO so polarity is not an option.

All towers are GPS sync'ed but we still see issue as the APs "talk" at the same time and a SM may "hear" two or more APs within the same channel. 

I have talked to other ISPs using 20MHz, but I wonder how close and visible thier towers are to one another.

We've been using 3655, 3667, 3682, 3695 with the PMP320 gear for some time now.  Currently we only have a couple PMP450 sectors. (2 @PMP450 vs 70 @PMP320)

Why are you maintaining a 10MHz guard band?  The PMP450 gear is supposedly capable of running with NO guard band, which would enable up to 5 un-reused 10MHz channels.  Our plan was to roll out PMP450 on the same four channels.

On the PMP320, we currently have 4 cases where we needed an extra sector overlaid for capacity, so we have frequency reuse going on three towers with no significant trouble.  (with the caveat that a customer 1/4 mile from a 500ft tower will NOT see enough SNR on a reused channel)


Thanks newkirk,

I think I may be testing 5 channels in the near future and see what happens. 

Another early thread on here discussed 5 non-overlaping channels and said it caused issues, so I've been cautious.


From the Config/User Guide (at least since 13.2):

In the 3.5 GHz or 3.6 GHz bands, no guards are needed if the ‚ÄúAdjacent Channel Support‚ÄĚ field is enabled under Configuration, Radio (this limits the SM Max Tx power to 23 dB combined). With 3.5GHz or 3.6 GHz SM transmitting at max power (Adjacent Channel Support disabled), the guard bands needed are: 5 MHz between two 20 MHz channels, 3 MHz between two 10 MHz channels and 2 MHz between two 5 MHz channels.


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Because we're in a very noisy area, I'm finding the uplink has far lower S/N than the downlink, so the sm transmit limit for Adjacent Channel Support was a problem.  I'm leaving 5 MHz guard channels out of paranoia, but by documentation 3 MHz is sufficient.  We also cannot use a consistent frequency layout because of all the noise; every AP has to have its frequency selected based on noise.

It's a good idea to get some SMs on every AP on a tower, and then do a sector spectrum analysis on all four APs at once.  By looking at both the AP spectrum and the spectrums for the SMs connected to it, you can find the best frequencies to avoid noise in both directions.

If noise isn't a problem and your only concern is self interference, then take a look at the "Multiple OFDM Access Point Clusters" section in the 450 Planning Guide at https://support.cambiumnetworks.com/file/313fdb2588920e279f0ec8831b30970540272351.  We did something similar with our 320s before background noise became a problem, and it made a huge difference.

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Thanks for the info Kirk and Ted.

Also on the subject, Cambium has an upcoming webinar on the issue.

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