brainwagon

With all the satellite mucking around I’ve been doing, I’ve been thinking about the possibility of building a little setup to receive weather satellite information directly from the weather satellites that are in polar orbit. They broadcast mostly around 137Mhz, and use an AM modulated subcarrier to send information via FM. I haven’t got a reciever yet, but I did manage to find a recording of the sound they make. I spent a few minutes reading up, and then in the next fifteen wrote a little page of code that decodes the images.

Bigger version of the same…

The code doesn’t find the horizontal sync pulses, and does nothing to adjust timing, so it drifts in a slightly nonlinear fashion, but overall, it works pretty well (for fifteen minutes of coding anyway). More later.

Addendum: In looking at the image, I determined that I was too aggressive in my filtering, which resulted in a considerable loss of detail. With a different set of filtering coefficients, I could generate a higher resolution version, which looks even better.

Better version…

Addendum²: Necessary technical information about the encoding scheme is here.

Addendum³: The sound file and some example matlab code that does the decoding can be found here.