If you have some old cassettes, a computer, and a love for obscure technology, here's a fun project to waste a couple extra hours on. Using a type of amateur television broadcasting that dates back to the early days of space travel, you can store and view images from normal audio cassettes, using only your computer and a tape player. And once you've figured out what you're doing, you'll be able to transmit pictures on anything that's audio-capable. And maybe actually learn to use the technology for it's intended purpose.
Before you begin, here's a few things you'll want to have:
- A computer with a headphone and microphone/line-in jack.
- A tape player with the same jacks, and a record button
- The ability to work on a pointless, and mostly useless project
- A lot of extra time to kill
That being said, let's learn a few things about what we're going to be doing.
Step 1: Slow-Scan Television
What makes this project possible is a type of television called SSTV, or Slow-Scan Television.
With normal television, about twenty five to thirty frames (pictures) are broadcasted per second, making a moving image on your screen.
But with SSTV, there aren't any moving images at all. Infact, all you see in the end is one, still image, which is only about 256×256 pixels large. To most people that probably wouldn't sound very exciting at all, but for people like me, being able to transmit even one still image makes my brain jump with excitement.
Usually, SSTV is used by amateur radio enthusiasts, who broadcast an image that includes their callsign and other radio-related things over the HAM or shortwave radio bands. SSTV is even used on the International Space Station to broadcast images of the station back to earth, and to anyone who's listening in with a radio. But in this instructable, we'll be taking the audio signals that make up our pictures and recording them, instead of broadcasting them. Because radio transmitters are expensive.
Even though we won't be using it for it's intended purposes, the way we use it is exactly the same as if we were using it over the radio. We use a computer program to turn our images into audio, and also play audio to the program, which will then decode it and show us the picture that's encoded in the sound.