We have several installations of PMP 450i APs running 900 MHz that have terrible signal quality to all attached customers. Obviously we are not doing something correctly. Our firm has 10+ years experience with PMP 100 in 900 MHz, so not complete noobs, but, as I've said, something isn't right. I can upload any requested files or additional information. Please direct me as to where to start.
Are you using the Cambium's OEM antennas for the AP and client? We've had mixed luck with these antennas for 900. We've been using KP's antennas and have had much better luck. We had two sites that we tried using the OEM 60deg antenna and we kept having re-regs, low modulation, probably because of farming SCADA in the area. We switched both sectors out with KP 13dBi 18" flat panel antennas (KPPA-900DP-FP), and although they're almost half the beamwidth as the Cambium OEM's, they perform well in the same target area and we went up 2-3 modulation levels on every client. We then swapped out the lowest performing clients with the KP 17dBi yagi's (KPPA-900DPY17) and now both sites are doing great.
Thanks for the reply! We too are using KP Performance sectors in 90 degrees. We are using the Cambium yagis on the SMs. (Cambium Networks - N009045D003A - PMP450i 900MHz 12 dBi gain Dual Slant Directional Yagi Antenna)
What I'm seeing is that you have low SNR in the uplink direction, and relatively high noise floor perceived by the APs. They're seeing something whether it's a competitor, other of your towers, or meter-reading gear I couldn't say. What sort of downtilt do you have on the AP sector antennas?
If vertical and the AP is not down in a valley then it's basically aiming at the horizon, able to see any other 900MHz band transmitters between it and the horizon.
Since you mostly seem to be seeing interference at the APs, (assumption based on the distant SM seeing clearer spectrum than APs - the nearer SMs are of course stronger since they're all seeing the tower's APs strongly) it suggests that their height and/or the fact that they're aimed at the horizon is allowing them to see interference sources the clients cannot. Which is why I asked about downtilt. (I encourage our guys to apply about 6 degrees downtilt and tweak from there if needed - with a 23 degree vertical coverage on the Cambium 900mhz sector antennas that's enough to significantly reduce interfering signals from neighboring towers and their client bases, though it's no help at all against the water meters that interfere with us in one county - maybe even makes it worse)