Do you have a ski pylon? If so they make extensions you can buy to put on top of them, same concept as a tower. It IS possible to make your own, just check out www.diytower.com
(I built my own as well, it's listed there). The pylon is definately the cheapest, and less problematic way to accomplish your goal. There is also pylon projects on that webpage as well, you may find it helpful.