WX Satellite Pictures

I've setup a WX satellite receiving station to receive weather pictures from the NOAA polar orbiting satellites. These satellites broadcast weather picture data on 137 MHz and can be received with a fairly simple station. The latest pictures my station has received can be found at http://oddjob.yi.org:8888/wxpics/index.html.

Hardware

The antenna used for the WX satellite receiver is a Quadrafillar Helix built by KE5RS. The antenna is based on W3KH's article in the August 1996 issue of QST. An antenna like this is needed for satellite reception because it has a good reception pattern. Using a vertical discone gave results that were not very good, as it started to fade badly as the satellite got higher in the sky. The antenna is mounted about 12 feet up on a pole. It hangs from a shelf bracket attached to the pole with some U bolts. The setup still shows some nulls, not sure if they are due to the antenna itself, or due to the environment around the antenna. Will probably add a mast mounted pre-amp and see if that helps out with some of the weaker signals. The receiver is a kit built Hamtronics R139 Weather Fax Receiver. The receiver is a is a crystal controlled 5 channel receiver that covers the currently active WX satellite frequencies (137 MHz)

The receiver has capability to scan the 5 channels, although I've not had good success using this feature, the signal level from the WX satellite are too variable to reliably use it in scanning mode.

The other unusual feature of the receiver is that is has a wide IF. The WX satellite signals AM modules audio on a wide bandwidth FM carrier. The bandwidth is about 30 khz which is more than a conventional scanner or VHF radio can handle, hence the need for building a special purpose receiver.

Software

The output of the receiver is an audio signal that is fed to a computer sound card and processed by the WxToImg program. This is an excellent piece of software that decodes the audio received from the satellite and produces the images shown on this web site. The pictures received from the satellite do not contain the map lines, they are added by WxToImg.

Once WxToImg decodes a picture a small script on the receiving computer moves the images to a Linux box running Apache that hosts my Live WX Sat Picture page.

Future Plans

I've had a lot of fun in putting together this WX satellite receiving system. I'd like to add computer control to the R139 receiver so I can have the computer automatically select the correct channel when a satellite pass is occurring. My current thought for this is to build a PIC based control module that would connect to the computer via USB or RS 232 and control channel selection on the receiver.

Update September 2005: I've designed and built a