Re: Solar Eclipse and Weather Sats

David J Taylor

From: dwight_talley

That is great Bob. Years ago when I was doing this there were several weather sats, both American and Russian. Now there are only a few running and all of the Russian ones are dead. If you didn't have a radio like the ICOM, you had to build a crystal controlled radio to receive the sats and feed the sound to your computer. Then they changed the frequencies and you had to try to find correct crystals. I wished I had a dongle then.

Yes, there are still three NOAA satellites on APT (137 MHz), and at least one Russian one which is now delivering data digitally on the 137 MHz band using a coding called LRPT. Instead of two channels there are three, and the resolution is some ten times better, so the image quality on 137 MHz can approach that of the HRPT images which are still transmitted on 1.7 GHz by the NOAA satellites. They can be quite stunning, and you don't even need a tracking antenna. Yes, they can be received with a low-cost dongle, or an Airspy receiver (others are available).

There is a plug-in for SDR# which decodes the LRPT data, and a Doppler shift module as well (although I've not found this necessary). IIRC there's a decoder which could take an IQ file from SDR Console.

It's a pity that NOAA chose not to equip the newer satellites with a VHF facility, which would have allowed an omnidirectional antenna to be used (useful for ships as well as amateurs).

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Email: david-taylor@...
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