Amateur radio is a hobby of mine. Actually signal processing is my hobby, amateur radio is one way to translate the hobby into something tangible. I've been working on a program that will capture NOAA weather images from the NOAA satellites overhead. This is one part of a larger system that includes an antenna pointing and satellite tracking system (completed) and a self contained software defined radio system (in progress). This little phase of the project was to write the software that turned the data into something fun - namely, a picture.
Below is the captured image of a NOAA APT slow scan picture transmission from a satellite pass over north america. The top of the screen is to the south, Baja is on the right, Gulf of Mexico on the left. The left frame is the visible spectrum and the right is infrared.
The satellite transmission is FM modulated on about 137 MHz. A radio front end performs the FM demodulation and translation to baseband and outputs the AM modulated subcarriers to my computer. My software streams in the AM modulated sample stream, demods the AM signal, finds the sync pulses and frames/decodes the image, and ultimately displays the result to the computer screen.
I need to fine tune the filter design as well as design a more intelligent coloring algorithm but all in all the features are pretty good and landmarks are obvious. When I get this done I will write the FM demodulator block so that no external radio equipment is required other than the basic RF front end; that is, complete the software defined radio block, which means no more handheld transceiver to do the FM demod.
When I get a decent antenna put together I will mount it on the tracking system I built and put the whole system operation together into a video.
The decoder software took longer than I thought it would but it did not require drinking (per Sparky's saturday night thread)
The "fun" part about this software is that it decodes in real time. That is, the image appears on the screen as it is received from the satellite. Typically people record the AM part and then run it through off the shelf decoder software that spits out an image. I wanted to be able to see it in real time - chirp by chirp.
The images are high resolution though this one doesn't really show it because of the photo hosting site. Generally they are 2080 pixels wide by however long you can receive the signal.
Thread: Another hobby thread