Why was the radio an important propaganda tool for the nazis?

The Nazis pioneered the use of radio to reach great distances and to a large audience at a relatively low cost. German propagandists were transmitting no less than eleven hours a day of programs, offering most of them in English as well. German propaganda minister, Joseph Goebbels claimed the radio was the "eighth great power". He propagated the anti-Bolshevik statements of Hitler and aimed them directly at neighboring countries with German-speaking minorities.