Depending on how high the aircraft is, you can usually hear an aircraft radio transmission for great distances. But, in order to hear any transmissions from controllers or aircraft on the ground, it's best to be within 10km (6mi) of the airport. And even that small distance can be a problem if there are buildings or other obstructions (tall hill) in between you and the airport. If you live at a much higher elevation than the airport and you have a clear line of sight to the airport, then the feed site can be further away. If you are 56km from LHBP and unless you live on a high mountain facing the airport, that is almost definitely too far.