WeatherScan 2.0 - Bringing back UHF SSTV

     For any newer hams reading this, SSTV (Slow Scan TeleVision) is an interesting mode in Amateur Radio that converts images to sound files, and the sound is sent over RF. The receiving station has some software that reprints the image line-by-line from the audio file that is received. Most commonly found of the HF bands, there can sometimes be SSTV found on the higher VHF-UHF bands, but it is quite rare. A fellow NOVARS member and I set off to design and implement a SSTV beacon that would deliver an image of the local radar on the top of the hour, and a forecast based off the late 1980's Weather Channel "Local on the 8's" style that sent at the half hour.

    A benefit of using SSTV is that no special cables or equipment is required, besides a way to receive the signal, and a device with software and a microphone. Non-hams can easily use a SDR to receive the signal, and smartphone apps for iOS and Android exist that can decode the signal.

    Our system started by setting up a Linux VM that runs on my server, and connects to a Motorola XPR 4550 UHF radio via a soundcard with PTT capabilities. We started by sending the radar image every hour on the hour. This uses a curl request to pull the most current radar image from a local NWS office in our area, ImageMagick's "convert" system is used to upscale the image to a size compatible with the PD120 SSTV format. From there, PySSTV is used to convert the resized image to a WAV file. HamLib's rigctld is used to PTT the radio, and the play function from the Sox library is launched in another terminal to play the audio. A CW ID audio file is played afterwards.

    This system worked well, and we knew that we could expand on it, so we quickly threw together a UHF copper pipe J-Pole to put with this radio, and set out to set up the Weatherscan style forecast. At the time of this writing, we are working to set up a GitHub repository with the scripts to make all of this happen, but in a nutshell, the script generates the image by pulling in a template image, pulling in weather data from an API, and places the text with the weather information onto the template image, then saves an output image (Update: The GitHub repository is now available at https://github.com/N1OF/WeatherScan-2.0) . The output image is sent in a similar style to the radar image as outlined above, but skips the curl and conversion processes, since the image was generated locally, and the image is already the correct size.

    We have had successful replies to this project, with several club members attempting the decodes using smartphone apps and HT's. A few example decodes are below. 

This is a decode from a NOVARS member of the half hour forecast image
using an iOS SSTV app, and holding a HT to the microphone.

This is a decode from a NOVARS member of the top of the hour radar image
using an iOS SSTV app, and holding a HT to the microphone.