ISS SSTV
The International Space Station has multiple Ham radios on board, and uses them for multiple purposes. Voice contacts with terrestrial hams, educational sessions with schools around the world, APRS, and Slow Scan Television.
Receiving the broadcasts is fairly easy, but does require some setup and equipment. And each mode is different APRS vs. SSTV), in this article I'll focus on SSTV reception. You need:
- A 2 Meter Ham radio with a decent antenna (nothing fancy, I use a copper J-Pole). You can even use an HT with a 1/4 wave antenna
- A PC (I'm using Windows, although there is SSTV software for both MacOS and Linux)
- Software to decode SSTV, I use RX-SSTV
- A way to get audio from the radio to the PC, I use a Signalink
The final step is the trickiest. You don't need to transmit for this exercise, but if you set things up with the option to transmit, you can do more things later. It's the same for receiving any kind of digital signals, so once you have all this working, you can use it with other software like FLDigi to try out other digital modes.
There is software that acts as a virtual sound card, so you just need to use an audio cable into the PC, and it will create a virtual port the decoding software can use. I've never gotten that to work on Windows, not sure if it's my PC or just user error.
I went the easiest route, and bought an external soundcard with a cable to connect to my radio. I went with the Signalink, a small and simple box. It has cables and interfaces to radios that have data ports (like mine) or just a mike and external speaker jack. For SSTV, since you're only receiving audio, there are a lot of other options, but I'm only going to talk about methods I've actually used. In a pinch, you can take a microphone plugged into the PC as the audio source, and set it next to a radio, but don't expect the best quality downloads.
With the Signalink, I hook the radio to the Signalink, plug the Signalink into a USB port on the computer, and tell the SSTV software to listen on that port.
For SSTV software, I'm using RX-SSTV, available at ON6MU's page. There are a lot of options available, and I've used several of them. I find this one the simplest to get going, it's not long on configuration options, but you don't need many of those to receive these broadcasts.
Now that you have a radio hooked up to a soundcard hooked up to a PC and SSTV software on the PC configured to talk to the soundcard, all you need to do is 1) tune your radio to 145.800, turn on your soundcard (if needed) and 2) launch your SSTV software and wait for the transmissions to get captured!
It's a good idea to watch a transmission come in, and see if you need to adjust your sound levels to get the best reception. Two great sites for tracking the ISS are AmSat and n2yo.
Other platforms:
I also have captured SSTV on a Raspberry Pi using the now built-in (on PiOS) PulseAudio as a software soundcard. I just needed to plug an audio cable from the radio to the Pi, and I used QSSTV as the SSTV decoding software. This combination gave me reasonable success.
A lot of good info on finding out when transmissions occur, how to locate the Space Station, and other fascinating information can be found here and here.
Once you're setup, you can look forward to receiving pictures like this from the ISS:
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