I wrote a low level code, without client repeating packing data for all clients in 2*29char packets and now it's running (very small distance) at 110Hz -> 4ms/packet without losses
I also implemented a small ping test to check if it's alive, all hardware test can be performed only changing the master settings.
I'll test in a long distance the system, in any case some packets can be lost without a visual impact
Thanks for help