I have 2 towers that are close enough to each other that they can see each other.
I am operating in the 3.65-3.70 band with 20MHz channels. Each tower has 4 APs, all GPS synced (450i).
When I set up the first tower, I did 3690 MHz for the north/south and 3660 MHz for east/west.
Now that the 2nd tower is online, I’m getting interference (did the same setup on that tower).
Would I be better off setting all APs on 1 tower to 3660 and everything on the other other to 3690? How should I deal with this?
Assuming you're using GPS sync on both sites, just use the opposite channels on the other tower... so keep your first tower at 3690 for N/S, and 3660 for E/W, on the second tower use 3660 for N/S, and 3690 for E/W.
Is there some downside to using the same frequency for all sectors on the same tower if GPS sync is used?
Also, if the 2nd tower is SW of the first tower, would alternating the frequencies as you suggested still work?
First question: Cambium does not support Reuse 1 (R1) for all sectors on a tower (like what is used in the cellular/LTE world). They only support back to back frequency reuse. Please read THIS guide on using GPS and frequency reuse (NOTE! while this guide is for ePMP products, the core principles are the same for 450.)
Second Question: Depends on the antennas used, antenna downtilt, distance apart, and other factors. Perform a spectrum analysis to see how 'loud' each tower can hear each other. If the sectors have over lapping coverage and can hear each other very well, then it might help if you added downtilt to the antennas, or perhaps rotating the antennas so that they're aligned in a better arrangement for multi-site GPS sync. Lastly, you could try using a smaller channel width on just the sectors that are interfering, like reducing down to 15 or 10MHz so that there's no overlap.
In every tower and sector keep same radio's parameters:
Max Range, Downlink Data %, Contention slot. It helps a lot.
All the towers must have gps sync, of course.