Radio21 are a local radio located in the mountains west of Madrid in the towns of Pelayos de la Presa, Robledo de Chavela and Navas del Rey.
Radio21 website address is www.radio21.es
If the Radio is extremely choppy and stops every 5 seconds, try listen to this Radio at different time.
Not all Radio Stations function for 24 hours everyday. If you can't listen to any Radio, try to listen at different time, as the Radio Station may stop during midnight according to its own country time zone.