SAN FRANCISCO (Reuters) - The U.S. evangelical broadcaster predicting that Judgment Day will come Saturday says he expects to stay close to a TV or radio to monitor the unfolding apocalypse. Harold Camping, 89, previously made a failed prediction that Jesus Christ would return to Earth in 1994. But the head of the Christian radio network Family Stations Inc says he is sure an earthquake will shake the Earth on May 21, sweeping true believers to heaven and leaving others behind to be engulfed in the world's destruction over a few months.``We know without any shadow of a doubt it is going to happen,'' said Camping, whose Family Radio broadcasts in more than 30 languages and on U.S. and international stations. His supporters have posted about 2,200 billboards around the United States about the coming apocalypse, and dozens of followers are driving across the country to spread the news. Volunteers also handed out pamphlets warning about May 21 as far away as the Philippines, telling people God had left clear signs the world was coming to an end.