Its a number station of sorts, more can be found explaining them on wiki (https://en.wikipedia.org/wiki/Numbers_station https://en.wikipedia.org/wiki/Numbers_st

Its a number station of sorts, more can be found explaining them on wiki (https://en.wikipedia.org/wiki/Numbers_station https://en.wikipedia.org/wiki/Numbers_station) and youtube (https://www.youtube.com/watch?v=SQbQTv3aMkU https://www.youtube.com/watch?v=SQbQTv3aMkU) (loads on youtube) I think the reason they have disappeared is because of the satellite coverage seen today, so people need to look in new places to find them.