We have set up a PtP link over a distance of 1.2 km with 2 LHG 5ax (24 dB version). RouterOS is version 7.23.3 on both APs, antenna alignment on both ends the best achievable (installed with the optional, adjustable pole mounts, completely free line of sight, using 20/40 MHz bandwidth. Country Czechia.
When using legal settings, with antenna gain set to 24, the signal strengths on both ends hover around -80 on both ends. The link connects stably, but with this weak connection there are really no margins for interference, or other adverse conditions. This link replaced a previous Ubiquiti AirMax link with omnidirectional base station, and the remote link with a 620 mm dish antenna. Signal strengths with that link and legal power was around -56 dB, that is, technically a far inferior setup.
Just for testing, I set the antenna gain to zero on both ends, which would give each AP max power. The signal strength with that setting is probably completely outside legal limits, and the signal strengths on both ends hovering at around -60 dB, which is not very impressive at that short distance. I cannot imagine that you could create a viable connection at a distance of advertised 20 km with this setup.
I would be very grateful, if somebody with better knowledge could give me some hints what is going on here.
Are you sure the AirMax was set to the proper power to compensate for the gain of that 620mm dish?
It would be completely normal to have 4dB more gain from that dish than from the LHG 5ax, assuming the XL version. For the standard version, the difference is even more.
I set the output power within the EIRP limits given by the software. I even had to reduce the output power of the PowerBeam, to keep it somewhat in line with the other APs connecting to the base station. It's bad practice to use more power than is warranted by the application, and the environment.
At the moment I'm using a fixed channel setup with 5680 MHz. I scan the frequencies on both sides of the PtP link now and then, and if one of the sides is more cluttered than I want, I select another channel. Presently, 5680 MHz is the best compromise. Also, it does not overlap with any local meteorological radars (nearest about 120 km distant).