The ISS Is Sending TV Signals to HAM Radio Nerds

HAM radio enthusiasts around the world are freaking out this week because they've had the rare chance to receive and decode television signals from the International Space Station.

The ISS is outfitted with an amateur radio that allows it to send and receive signals from Earth. Astronauts aboard the spacecraft occasionally use it to communicate with students as a whoa I'm talking to an astronaut from my classroom sort of exercise. There have even been times when bored astronauts have turned on the radio and started talking to random people around the world.

But every once in a while, the ISS has an announced "event" where it broadcasts signals to amateur radio enthusiasts. This week, it's sending out what's known as "Slow Scan TV"—radio waves that can be decoded and turned into pictures. The technology is how we first sent images from the moon to Earth.

"Unlike normal television that takes a lot of bandwidth, it sends it quite a bit more slowly on narrower bandwidth," Ryan Reynolds, an amateur radio operator who received the picture you see at the top, told me. "It took me three minutes to get a full picture."

The images seem to mostly contain waving astronauts, though a few people have scored space race-era images from both the Russians and Americans on the station. The images do indeed come from audio—it sounds like this:

People around the United States have had mixed luck grabbing the signals—a cloudy night, interference, or a lackluster antenna can garble the picture. Few of the images I saw were quite as crisp as Reynolds's.

Reynolds says if you know what you're doing, it's not a particularly expensive or difficult hobby to get into.

"There are guys doing this with homemade antennas that are $20-$30, and a handset radio can cost $30 on Amazon," he said. "From there, the software is free, you can do this."

He's not wrong—here's one antenna a Redditor cooked up in the laundry room.

There are a lot more images here.

Correction: An earlier version of this article said a HAM radio license is needed to receive SSTV signals. It is only needed to transmit signals.