Usually, if the old dish is not damaged, then it's performance more or less the same as a new. But you can be a first one to check whether it is like that..... buy 20y old one and another one completely new, install them side by side and do some testsThe only thing that worries me is that the disk is over 20 years old. Is there a difference in the quality of the reception, maybe the newer discs have a better center for receiving the signal?