For project updates, visit: AgriVision - Raspberry Pi SSTV Camera.
The goal of this project is to use the Raspberry Pi with the PiCam as a wireless camera which can transmit images over long distances, usually tenths of kilometers. Images will be transmitted by amateur radio (ham-radio) using slow scan television (SSTV) on the 2 meter band (144.5 MHz).
Since the Pi can generate the HF FM signal itself, no additional electronics are needed for low power transmissions. For a little bit more power a one or two transistor amplifier will be suitable. Furthermore a low pass filter is recommended to filter out higher harmonics of the signal.
This project also contains a python script which detects movement. Using this script the Raspberry Pi can be used as a wireless security cam at distances far outside the range of normal WiFi networks.
Be aware that you need a ham-radio license to use this application!
Here is a video of the camera in action:
Step 1: Capturing the image
First thing to do is capturing the image we want to transmit. This can easily be done with raspistill:
raspistill -t 1 --width 320 --height 256 -e png -o /tmp/image.png
For sstv we need a small image, of 320 x 256, it is saved into the /tmp directory as png.