Observation 978496: NOAA 18 (28654)

Regarding Observation 978496 … station has accurate time but I’m still seeing doppler. Any ideas? Also, decoding isn’t working, any ideas on that?

This is the ARGOS signal in the UHF band. From what I can tell, this signal is not usually active. What you are seeing are most likely terrestial signals.

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+1 I don’t think we have any successful observation of NOAA on UHF.

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what would be a good satellite to observe to validate my station?

For UHF you can start with 40043 TIGRISAT and 40012 UNISAT-6. Both transmit continuously a strong signal.

You should expect to see their signal at the middle of the waterfall following a straight line. Also both are decodable by gr-satnogs scripts, so if your reception has a good SNR then you should see also decoded data.

Trying to fine tune my LNA on my UHF station and I was scratching my head as to why I couldn’t schedule any Unisat-6 passes… FYI (to anybody that doesn’t know), Tigrisat and Unisat-6 have almost identical tle’s… so you likely won’t be able to schedule both.



Observation 991871 is 40012 and it looks awful. doppler and weak signal.

Unfortunately there isn’t any signal from UNISAT-6 in 991871. The lines and the signal you see comes from terrestrial sources. You should expect to see something like in this observation.

OK, I understand - the doppler is actually the “reverse” of the doppler compensation for the satellite, appearing on the terrestrial signals. so… any hints as to why I am receiving a terrestrial signal and not the satellite? There is some signal in there. and other satellites I observe show signals too - so my station is receiving something…

I’m determined to the get to the root of this… I have scheduled 4 observations over the next few hours: 996860-996863. All are with satellites with 90-100 success rate, all with max elevation 70-90 and zero overlap. The last one ends at 06:18.

The signals you are seeing are most likely intermodulation products of other strong signals (not necessarily within the passband of the receiver) forming in your receiver chain. The signal in observation #978496 does looks to me like some kind of terrestrial SCADA link.