Receiving and decoding weather satellite pictures are quite interesting and only require modest efforts. In the late 1980's I built a WEFAX scan convertor from a series of articles in VHF communications magazine- it was primitive but worked quite well. Initially I used a simple receive convertor that converted 137 MHz signals to 28 MHz and used a communications receiver to decode the signals. The quality was rather marginal because of low signal levels, also the narrow filter bandwidth of the communications receiver produced lower dynamic range of picture grey scales, but it got me started. Next, I bought a Hamtronics R137 receiver kit that was designed for WEFAX decoding and that made a big improvement in picture quality. Many hours were enjoyed watching weather pictures using this simple setup.
After a hiatus of several years, the WEFAX equipment was revived with new interest. Sound card-based decoder software on the PC produced superior pictures to the old hardware scan unit and the old hardware was retired. The new software was Windows-based, was easy to use and much more sophisticated than the hardware-only approach.
When I seriously started using Linux, I discovered the WXTOIMG software package, which is remarkable in its own right. Not only would it track atellites and know when to start and end decoding, but also added geographic borders, and false-color landmarks. Watching these weather pictures unfold before one's eyes is a lot of fun. I highly recomment the WXTOIMG software.
At this point, only images from polar-orbiting satellites were processed. These satellites generally are closer to earth and produce fairly good resolution images. One can easily make out landmarks and get a good idea of imminent weather. Polar orbiters scheduled passes, however, may be infrequent and often be far to the East or West of the area of interest. For this reason I became interested in the geostationary weather satellites, particularly GOES-W. Living in the Northwest, that satellite is visible from my location. It is parked in the Clarke belt alongside other geostationary satellites, located at 135 degrees West. It broadcasts WEFAX in the L-band on 1691 MHz on a continuous basis, thus giving one the ability to observe the weather more readily.
Expectedly, working in the microwave range of frequencies is a little more challenging than dealing with the 137 MHz equipment used for the polar orbiters. Some years ago, I was fortunate to come across a 1691 to 137.5 MHz downconvertor and low-noise preamplifier built by MicroWave Modules, Ltd.; it was time to put it into service. That was simply a matter of finding the right type of connector and bringing power to the units.
The other challenge is a suitable antenna. Fortunately, I had a small unused 5-foot TVRO dish in the backyard at my disposal. A small 2.5-turn helix and reflector was fabricated and fitted to the dish's prime focus using the dish's existing hardware. The pre-amp and downconvertor was simply hung off the N-connectors mounted to the
helix's reflector
and
enclosed in the TVRO's old weather cover. Finally, the convertor's 137.5 MHz output is brought into the shack with a short run of RG58 coax and fed into the R137. All that remained was to peak the dish up a bit on the satellite for maximum signal and it was ready for use.
Examples of the pictures from polar-orbiting satellites and this one. Pictures from GOES-W (full disk) and GOES-W (NW sector). These were decoded using WXTOIMG on a Linux computer.
73, de KC7WW.
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