Well, hang on. Isn't he saying he wants to put the controller 20 ft away from the first node? OTOH, he might just squeek by if the distance os no more than 20'. At full draw, the voltage drop across the Cat5 would be right at 1.52 Volts, which might be OK - maybe.
Personally, I would definitely recommend putting the DC power supply at the tree. The dongle can be behind the fence, but I would insert the power as close to the first node of each string as possible. That means putting the Zeus or hub at the tree. That, unless he wants to breakout the power leads at the tree and run a pair of #6 or larger power leads from the power supply to the tree.
