First thing to do is to call for locates. Digging into a cable can be very expensive, and possibly fatal. http://www.on1call.com/
Secondly, I would suggest that you use a 3" diameter pipe, into a 8" diameter hole at least 4' deep. And as Misfish says mushroom / \ the bottom of the hole to prevent lifting. If you decide to use the wood pole, it would be best if you can have a minimum of 4" of concrete around the pole. To lift, tuck the end of the pole in the hole, lift at one end with a couple of guys and let 'er drop in. Plumb, brace, and pour concrete.
Good luck.