Depends on who you ask. I am using 16 ga stranded on a run of less than 100 feet with no problems. I have been told that no smaller than 12 would work and I would have a fire in the ground and my dish would melt from the strain, the satellites would stop sending me signal, if I used smaller than 12ga. Mine works fine.
Here lately I have seen a lot of talk about the seven conductor sprinkler wire, and it is
18 gauge, and I bought 100 feet of that to use on my Birdview, which isn't together just yet, so I cannot tell you how it works. But past reports point to good performance if the distances are kept reasonable.
If you have longer to go, bump up your size a couple to compensate for the long run.
Servo wire, OTOH, I am sure can be as small as 22ga. On all the dishes I have wrecked it was tiny, tiny.
I hope some of that helped.