Hi Jonas,
I actually used a CAT6 cable and not CAT5 kramer cable. I used a power supply, but only on the transmitter (the receiver don't have a power supply).
Now i have solved with video Cables To Go TruLink 89037 - 1 x 1 - UXGA - 50 m (http://www.dgstore.it/connettoreprolunga-video-cables-trulink-89037-uxga-p-334955.html?cPath=0_90160_10769) it's cheaper and transport the signal with 2 different CAT5, 1 for the DCC and another one for the video.
thank for your suggestion
Emanuele