Why can't i get PBS in kansas using antenna?

Unless you have a digital converter you can't get any transmissions by antennae. Digital transmission has a much shorter range than the former analog transmissions did by about 50%. So, if you had gotten PBS by antenna before 2006 and can't now, with a digital converter, it may be that the station is more than 50 miles away, and the transmission no longer reaches your area. Cloud cover doesn't help digital signals, the way they did analog signals, either, in extending transmitting distances beyond the normal range.