Early air checks of WXRT are rare. The first clip above features snippets from the station recorded between 1975-8. Not a full air check but interesting nevertheless. The station began as a part time progressive station in 1973. You will hear some of the music heard on prog stations during this time and also the intro from a Santana concert simulcast on WXRT and channel 11.
The quality of the tape is not the best and I played it through my AM stereo transmitter and received on a Sony Radio.
The second clip has a very short segment from WSDM FM Chicago from perhaps 1976.