After having many hanging bird feeders attacked, chewed, and knocked down by squirrels, I finally came up with a low-cost solution. I purchased a 4"x10' abs pipe, and a 3/4"x8' electrical conduit. I cut the conduit in half, drilled a couple of holes in the pipe, and sunk the pipe 2' into the ground. Some spray paint made the pipe presentable. The pipe is wide enough that in 3 years, only 1 squirrel has managed to shimmy up it. A coating of silicon spray stopped him. It was really funny to watch him jump onto the pole then slide to the ground. 6" diameter pipe would be even more effective, but might seem too massive.