Thursday, 24 July 2014

APT weather satellite pictures

Back in the late 90's I realised a long term goal. I bought and built a weather satellite receiver. The kit was developed by a group called RIG (Remote Imaging Group) and sold for around £100. A good few thousand of these kits were sold worldwide. I even bought more of them to give away to local schools.

Its now 2014 and this kit has run its course but look closely on Ebay and you'll see that they are still available. RIG has been selling them for a closeout price of £50 plus shipping. As I had given away my last one to UACNJ I grabbed me another kit.

The finished kit in its new housing

I also made a few modifications. The kit would normally have a single 7 segment LED to indicate what channel it was tuned to. You could also add a signal strength meter to give you some idea as to how well you were hearing the satellite. I decided that I wanted a LCD rather than an LED. It would make the project look a little more modern. To that end I designed a LCD interface around an Arduino. I drew heavily from the work of Grant Zehr, WA9TFB. Grant had earlier designed a similar LCD display based on a PIC16F84 but it was limited to displaying only a few channels because the chosen PIC was lacking input and so could not read the entire state of the LED. The Arduino doesn't have that problem.

The Arduino LCD expansion board

In addition to the LCD expansion board I created a breakout board to better handle the large wiring loom that connects all the controls to the actual receiver. This board also manages the master power switch as well as supplying power to the LCD board.

The breakout board

To my surprise it all works! I've not finished putting holes in the enclosure yet but the receiver and display work very well. I have populated the channel table in the Arduino with some information about the satellite that is on a given channel so that one can see more than just "4" or "9". The Smeter is also displayed as a bar graph on the lower left of the display when receiving a satellite.

The whole project undergoing testing

Looking for satellites

The next step is to connect it up to a spare PC so that I can display the actual pictures the receiver gets. I'll make these available on my website too.
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