We have a strange problem.

With a 2km link using RB433 and R52Hn we see about a 10-15 db difference in signal between chain 0 and 1. Both ends of the link use the same cross pol panel antennas. When we swap the antenna ports at one end of the link the signal stays the same. When we swap both antenna ports at both ends, the signal remains the same. When we swap one end with a completely new router, the signal remains the same.

Spectrum scan shows no interference. Snoop shows no traffic. Signals are in the mid 60 and high 70s.

It just is the weirdest thing. Any ideas?

This is common. no antenna. no cable. no wlan card. no nothing is the same. The major issue is likly the channel you use, and the antenna profile. The antenna always have to compromize. spektrum, size, freq, polarization and gain. not possible to get it all. There is also no way. (almoust) there is no interferrence to annyting.

We are not talking about a minor difference. This is a 15dB difference between chains 0 and 1. The difference is persistent across swaps of antennas, processor boards and radio modules.

When we back down to 4.17, the difference goes away, so it must be related to drivers in ROS5 and 6 with the R52Hn and RB433AH combination. Just bizarre.

I´ve had a lot of problems with bad wireless cards. As you said... everything is changed even connectors swap doesn´t help one chain is still worst then the other... it is a bad radio card (if you are lucky as me, then you can also have 70% bad wireless cards...)

Perhaps intervening obstacles are absorbing energy of one polarity much more thoroughly than the other. Rotating the antenna so that you use two 45* planes, rather than H/V, would answer that question.