Observation #19854 - NOAA 18

Hi Guys,

Got my first station (https://network-dev.satnogs.org/stations/247/) up and running and been doing some observations during the day. My setup is basically a 137Mhz turnstile antenna, no LNA and rtl-sdr (RTL2832U). I’m using a raspberry pi 3 setup with the satnogs image.

It seems generally successful in terms of getting signals. I’ve tweaked things a bit and the latest observation especially seems good? (https://network-dev.satnogs.org/observations/19867/)

None of then are getting decoded APT data. Is this type of file still not good enough to decode the data or is something else wrong?

I did discover in my /tmp/.satnogs/data folder that I have an data_19854_… files for each of the NOAA observations, but the files is 0:

-rw-r–r-- 1 satnogs satnogs 0 Mar 30 15:27 data_19839_2018-03-30T13-27-31.png
-rw-r–r-- 1 satnogs satnogs 0 Mar 30 17:47 data_19848_2018-03-30T15-47-32.png
-rw-r–r-- 1 satnogs satnogs 0 Mar 30 17:08 data_19853_2018-03-30T15-08-18.png
-rw-r–r-- 1 satnogs satnogs 0 Mar 30 19:26 data_19854_2018-03-30T17-26-40.png
-rw-r–r-- 1 satnogs satnogs 0 Mar 30 19:52 data_19867_2018-03-30T17-52-00.png

Does this happens when the signal is bad?

Any insights would be welcome.

Last quick question, should my groundstation be running on dev or on production server?

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Your RF frequency is off by several kHz, so you need to adjust the PPM somewhere in the config. The signal on the waterfall should be centered around 0 Hz.

Frequency error in FM will manifest itself as DC offset in the audio. If the frequency error is severe, which is the case here, the audio will get distorted. You can both hear the distortion and see harmonics in the audio spectrum. I think that’s the reason why the decoder can not decode it.

Compare it to the audio form one of the good NOAA receptions, e.g. https://network.satnogs.org/observations/102852/


Yes, I noticed that as well. I spent some time now working on the PPM and waiting for next couple of observations to test it out.

But basically wanted to make sure that the way it is currently behaving (0 sized files) is because it can’t decode it due to bad audio or bad setup.

The offset seems better with the new observation?


Signal doesn’t seem like it was great though

Your station should be in production server with the testing flag enabled. Welcome!

Minor tip: if you use rtl-sdrs make sure to at least get a decent rtl-sdr (like the latest from rtl-sdr.com) which seem to have ~1ppm error max.

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Welcome to the Network!

Check also this guide for fixing ppm. https://wiki.satnogs.org/Adjusting_the_SatNOGS_Client

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Try a reboot!
Maybe some of the files in /tmp have changed the owner with your experiments.
You could try to fix that manually, but a reboot is less work :wink:

I adjusted the PPM and everything seems a lot better. Got some images now, and also managed to decode telemetry from Nayif-1 and FOX-1D. Having lots of fun :slight_smile: