For those looking at chain link top rail; Lowe's stocks 1 3/8" 18ga 10' sections and Home Depot stocks 1 3/8" 17ga 10' sections. Actually, I think both of them are 10'6". Both stores can special order a selection of thicker, heavier, and longer pieces. Look and see if 1 5/8" 16ga 21' or 22' sections are available at your store or even a local fence installer.
I just put up a mast today. I used (2) 10'6" 1 3/8" 17ga sections from Home Depot. I used a water drill to bore a hole for the bottom piece. I ended up sinking the base piece 6' in the ground. No cement!!! The base was actually 6'6" cut from the swaged end of one of the pieces. When I put the remaining 4' piece on it as a test I found the joint quite loose. Obviously it isn't gonna jump off but it is gonna wobble without some bolts or a support from a skyhook(or the side of the house).
So what I ended up with is 6'6" in the ground, 10'6" on top of that, and 4' on the very top with an A99 mounted to it. Knowing what I know now, I would go with a single 20'+ piece and avoid the joints. Mine is easy to lower and erect though.
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