Project for fun: storing data on cassette tapes

I’ve always been interested in the idea of storing data on audio cassettes, so over the past two weeks I’ve written a program that converts data to sound, and another one which converts the sound back into data. The project is pretty much finished now, and I can store about 1.4MB of data on an 80 minute cassette and retrieve it reliably.

The system I’ve developed works by playing a tone which is at a constant frequency of about 3127 Hz, with variations in amplitude which represent two different values, binary 0 and 1. Here’s an example of what the wave data looks like: http://dusthillguy.ddns.net/folder/files/quickupload/waves.png
I recorded a video of the system in action: https://www.youtube.com/watch?v=Yj2eUKC0uPs

The program is written in BBC basic and seems to run OK in RISC OS, though it was developed on Linux using the Brandy BBC basic interpreter.
The code is here if anyone is interested: http://dusthillguy.ddns.net/folder/files/quickupload/TapeDataProg.zip (by the way, it’s probably not at all well written, be aware that I only got into programming about three months ago)

That’s really a cool idea :)