Oops. No dish yet.
The bet way to do that is to remember that, of the last 200 big dishes you have seen, only a small fraction of those are working.
You go around looking for big dishes (solid, spun aluminum is the best, but small hole mesh is OK) where a little dish is mounted on the same property. Generally that means they have given up on the big dish and may just give it away. I got an eight foot solid that way, and I got a Birdview 8.5 dish that way. Both free.
Get whatever pole it's mounted on too. I am not one who advocates digging it up out of the ground. Just cut it off at the ground with a circular saw and black cutting blade.Fast. Easy. When you decide or actually get it, take pictures of the dish, especially of the mechanical workings on the back. Post them and the guys who know more than me will tell you exactly what it is and how to do it.