I'm new to all of the new TV technology and have a basic question. I currently have a Sony Trinitron KV-36FS100 without cable or satellite, just over-the-air channels with a roof antenna. I was told that I can purchase a digital tuner that will improve the picture and sound quality of over-the-air signals and possibly pick up additional PBS signals. Is this true? If so, can someone recommend a digital tuner. Is this what is meant by HD? Thanks for helping a rookie.