A pocket-size shortwave radio.

For three years, Mr. Chen looked forward to the hours after curfew. With a blanket wrapped over his head and the radio's metal antenna parallel to his body, he lay still as the vibrating device under his ear brought to life a world outside the prison's walls. Petitioners, protesters, human rights abuses, a grassroots movement to cut ties with the Chinese Communist Party (CCP)—in that tiny murmuring voice, he saw them all. He was free.

Over the decade since Mr. Chen escaped to the United States, the pool of Western broadcasters for information-hungry Chinese like him has shrunk considerably.

Radio powerhouses—BBC, Deutsche Welle, Voice of America—have either cut back on their China service or moved programs online. Meanwhile, the "Great Firewall," the regime's censorship apparatus aimed at isolating China digitally, seems only to grow taller by the day.

Bucking the trend is a largely volunteer-run radio network called Sound of Hope, whose 10 p.m. and midnight segments kept Mr. Chen informed about current affairs in China during his years in prison.

The company now boasts one of the largest shortwave broadcasting networks around China, with about 120 stations beaming signals to China 24/7.

Allen Zeng, Sound of Hope's co-founder and CEO, sees shortwave as the answer to the regime's information blackout.

"They can turn off the internet, carry out the killing, wash clean the blood, and turn it back on," he told The Epoch Times, pointing to Iran's pattern of blocking the internet during nationwide protests.

With shortwave radio, though, "they have nowhere to turn it off," Mr. Zeng said.

"It's like the rain falling down from the sky—they have no way to block the sky."