900Mhz sector antenna cluster physical layout

I'm contemplating putting up a 900Mhz cluster using Cambium's sector antenna's. I've read various things about how to layout a cluster but there seems to be conflicting information. I know from a cambium presentation on the 450i 900mhz that the antennas can be placed back to back on the same pole - however in the same presentation it was mentioned that horizontal seperation should be approximately 3ft. But, I've also read 10ft vertical seperation is another acceptable layout. Is there any official infomation (i.e. best practices) on how these antennas should be arranged physically for 4 antennas per tower or 6 antennas per tower?

Secondly does gps syncronization help if you deploy 4 antennas on one tower and use 4 different channels (5MHz channels, ignore any network wide sync issues)? Can antennas self interfere with other antennas on different channels or only self interfere from antennas on the same channel?

I'm just starting to learn about this stuff and willing to read if directed where I can get the information.



Yes you can use the antennas placed back to back with the different channel frequency configured or you can use the same channel frequency (With Synchronisation). There is no need of vertical seperation in PMP 450/450i so you can places in a ring manner (Cluster) in horizontal with 4 or 6 radios in the ring depending upon the installation you required.

If you place more than 1 AP on the same tower you need to have the GPS Synchrinisation which will help you in avoiding the self interference even from the same channel as well as other channel of the same frequency band.

Please feel free to let us know if you have any other queries.

Thanks for the response. So is there a radius recommendation for the ring? Or just pack them in as tight as physically possible and then also use gps sync?


You can use the linkplanner file from the below link where you can plan the installation and the antenna tilt and direction.


It is recomended you contact your RTM so that they can plan the link for you.

Please feel free to contact us for any queries.

Thanks for the replies, but does anyone have any real world expierence on how they setup up a tower antenna cluster? Any problems mounting antennas too close to one another? How far did you have to seperate them? etc.

Since the Canopy system uses timing, you can mount these units as close or as far apart as you'd like.  We have installations with 2 of these stacked on a mount with about 8" between them vertically, and installations with 4 units mounted 90° apart on a guyed tower with a 6' face and 2' standoffs, making them ~9' apart.

Thanks acherman, much appreciated.