Equipment update by April 2019
I given two completely different answers to the following.
I was told by 3/4Technical support people I spoke to at length who also said they had tested my old (installed in 2007) round dish that it is compatible with HD and that all I need for the future is to ask Directv for an HD receiver to receiver all the channels I now receive as well as all local channels.
Yesterday or the day before, a Legacy person told me I had been given mis-information, and that my old dish is not HD compatible.
I have since read that the new slim-line dish is not nearly as strong, sturdy as the older dish.