Setup for weather satellite GK-2A

[Learjet]

If you've been following the Himawari 8 thread, this is a similar venture but different satellite. In July of this year, Korea replaced it's ageing Coms-1 geostationary weather satellite with a brand new one called Geokompsat 2A or GK-2A for short. This satellite can be received directly on L band. The easiest transponder is the LRIT one on 1692.140 mHz. At first they carried a few different channels so colour images were possible, but unfortunately they now only have a single IR channel, though it is full disc at 2200x2200 resolution. If you want more channels there is always HRIT or Ultra HRIT but these need enormous dishes and more expensive receivers. The LRIT transponder only needs a small dish and an SDR to receive!

So here's what I did. I already had a spare 2.5 metre solid dish just laying around so put it to use for GK-2A.

Here it is here (left) next to the 2.3m dish for Himawaricast on Jcsat2B (right).



GK-2A is located at 128.2E, a little above Asiasat 9.

So I needed to make a feed. A can feed seemed logical so after some looking around I found people making them out of old Milo tins! I just happened to have some Sustagen tins that had nice yellow caps so I used that instead.



Inside is a quarter wave feed pin. I used a can opener to cut off the end (not shown).



I mounted this inside a can pan to make a kind of choke ring. Stuffed if I know what the illumination pattern is, but it looks good!





Next to a C band feed.



I bought a Nooelec SDR as this one has extended range to over 2 gHz, the cheap ebay ones are crap and don't make it to 1692 mHz.
I also bought a Nooelec Sawbird filter that has a 2 stage LNA and 80 mHz band pass filter. This gives 30dB. However I have also used
2 ebay $4 L band inline 20dB amps and they work fine too.



My SDR waterfall display looks like this.



I purchased Xrit decoder from USA-Satcom for a very good price, but if you're good with Linux, Sam makes great software for GK-2A for free!



An image comes down every 10 minutes around the clock.



The end result is this.



I used an overlay map from the GK-2A internet server and overlayed it in Photoshop.



That's it! Not colourful but fairly easy. Maybe they will add some more channels to the LRIT transponder in the future for colour.