Since the dawn of wireless communications, international broadcasters, including the Voice of America, have used shortwave radio to communicate with the world. While many broadcasters now are switching to other technology to get their broadcasts out, privately funded religious organizations in the United States still are devoted to shortwave.
Everything is set for a broadcast to the world at Christian radio station KNLS . It goes out in English, Chinese and Russian.
With the rise of the Internet, some news broadcasters, including the Voice of America, are moving away from shortwave radio.
But some religious broadcasters in America still believe in the medium.
"Our view is that there is a great future for shortwave," says Charles Caudil, president of World Christian Broadcasting, which runs KNLS. He says its long-range signal is ideal for reaching rural areas in the developing world.
"Very few people there have the Internet available to them, or satellites. But they do have shortwave receivers. There are about three billion shortwave receivers in the world," he said.
World Christian Broadcasting was founded three decades ago by former Army Lieutenant Maurice Hall. He helped to set up a shortwave facility for President Franklin D. Roosevelt's Yalta summit with Churchill and Stalin.
It is now one of the biggest Christian shortwave broadcasters in America. From its studio outside Nashville, Tennessee, it mixes cultural programming with the Christian gospel.
And it seems to work. Fan mail arrives, and Bibles are sent to those who want them.
The outlet is building a relay station in Madagascar, which will open a door the Muslim world.
Egyptian-born Tony Tadros of the new Arabic service and his colleagues at World Christian Broadcasting say they respect Islam. But they argue that Arabs are now ready to embrace religious tolerance.
"Most people in the Middle East, they have misconceptions about Christianity," Tadros said. "They think that the Bible is corrupt and they have a lot of misconceptions that they just got through the years."
Convincing them otherwise might not be easy. Many Muslim countries ban Christian proselytizing. And some converts have been arrested or faced death threats.
Abdullah Antepli, the Muslim chaplain at Duke University in Durham, North Carolina, says authorities in those countries consider those leaving the faith a threat to Islam.
"Not only a threat but an attack, also a violation, as they understand [it]," he said.
This American imam condemns that view. He says it does not live up to Islam's own ideals.
Spreading the faith is both a Christian and Islamic tenet. And these days, technology makes that possible on many platforms - television, the Internet and even mobile phones. But World Christian Broadcasting still has faith in shortwave radio.