I believe that when we say that this is radio telescope, it means that reciving frequency of it is in radio band. And also it means an observed object by that is in a particular redshift that its emission has a particular frequency that when recieves us, is in radio band. Am I right? For ex. We say cynus A is a radio galaxy. But it doesn't mean that it emits in radio freq. So it doesn't give us any info about physical activities happening in the galaxy, it just tells us about its distance from us. Sorry for my confusing question! I'm just wondering observing fre just tells us about distance?