Is it possible to have two radios (one XR9 and one XR2) on each end, and automatically failover between them? It must work as a bridge though, no routing (need L2 multicast/broadcast traffic to pass over it). I see that WDS has a link cost, so I thought that maybe WDS handles this already based on the throughput estimate. I don’t care about increased throughput, again this is for a mobile vehicle, I thought that maybe where 2.4 won’t reach, maybe 900 will and vice versa.
Cheers,
Matt
I agree that 900MHz in theory goes further than 2.4, however this is on a mobile vehicle for urban environments. The vehicle is constantly moving, and there are situations where 2.4 will reach, and 900 will not. The size of the antennas required at 900MHz to have the equivalent 2.4GHz EIRP is not practical on a vehicle for one. The 2.4GHz antennas we use are multi-polarized and perform well in a highly reflective/multipath environment (tested these in an industrial park with steel buildings everywhere, over 700m non line of sight with 30dBm cards). The 900MHz XR9’s seem to be very good at getting through obstacles that absorb 2.4. I just got back from testing out the XR9 pair in a suburban environment with a pacwireless 5dBi omni 17.5 meters AGL, and a 7dBi magnetic mount on the car. Covers most of a 500 meter radius reliably with plenty of suburban houses in the way 
Longest link was 880 meters, where the elevation was 6 meters higher than the antenna .. most of the time I can ‘see’ the AP with a scan, but I can’t associate to it, likely because of the lack of height of the vehicle antenna.
I’m currently using a pair of RB411’s so I can’t try both cards at the same time. If someone can tell me if it is possible to failover between radios (and maintain a bridge) (EoIP, WDS, bonding??), I will go pick up some RB433’s or RB493’s tomorrow.