Though he had never visited Earth, his great-grandfather visited the planet and brought back records. The DJ loved the sound of the old American DJs and based his style of presentation on them. The DJ had an English accent but used an American one when playing music. From his studio, the DJ could see use cameras to look into Tranquil Repose and the surrounding area. He could also communicate with people over an intercom.
When Tranquil Repose had been taken over by the "Great Healer" (Davros), DJ still played his music since, although Davros considered him aggravating, he was useful in keeping the Resting Ones distracted. When the Sixth Doctor and Peri visited Tranquil Repose, Peri went to see the DJ, seeing his program and thinking he was from the States. Wanting to capture Peri, Davros sent his Imperial Daleks to retrieve her and destroy the DJ.
While Peri used the DJ's radio to tell President Vargos, who was arriving on the planet for his wife's funeral, not to land because of the Daleks, the DJ rigged up an ultra frequency gun of Rock n' Roll. When the Daleks arrived, he destroyed two of them. When he got up, however, another Dalek entered and exterminated him. (TV: Revelation of the Daleks)