Hello Andreas, I have looked at the wiring diagrams for the WX 11, and there is no specific cable called out. If you put the processor on the rear avionics shelf, 25 feet would be a very generous length of cable to use. The cable could be field assembled. This is different than the WX 1000 which does have a specific cable to be used.
I normally put the antennas for stormscope in the bay just in front of the rear tiedown. This keeps distance from the pitch servo if you install a STEC or Century Auto pilot.
jvb