I put in a pole of about that height for my night light. I used my 12" standard auger and let it go as far as it would. Used my FEL to get the pole in the hole; worked great. Then filled hole with concrete. No problems. The use of ground wires as mentioned makes for good insurance.
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Tried the local guys with the towers and too many trees on both ends even though there is a valley between us. Tech has to set up your system and zero your antenna. He has to install it. On a 20' pole?????
Giving up on that I went with the Satellite, more expensive, but no choice on the matter.
Around here we use Excede and Dish (buys service from Excede and uses same equipment and satellites) satellite nets Since we have Dish satellite TV we get a discount for bundling. They are pickey about how/where you mount the antenna. Seems the beam is very narrow and the satellite is 25k or thereabouts miles in space in the synchronus arbit region. A few seconds (degrees, minutes, seconds) of pointing error can completely miss the target. I have a pole mounted and roof mounted. The pole is 2 3/8 tubing in concrete and about 4' off the ground. Excede is on that one and they installed it as Dish did the roof mount. It is in a protected area of the yard and is sturdy.
One of your first problems is getting the tech up the pole to zero it in. Excede uses a tone for zeroing and the guy has to be next to the antenna to hear it.
Down here the looking angle is about 30 or so degrees up in a SW direction. You might do better to cut some trees and install it in the conventional manner. Actually when you get your service, it's a requirement that they install it as they have to go through the hookup software so that the satellite knows that you are down here.
HTH,
Good Luck,
Mark