Regarding Observation 10450088 …
No signal in waterfall, but data was found. Am my team and I are new to satnogs, could somebody give an overview of reading the waterfall, or is this just random gibberish collected from the noise?
What you are seeing in this pass is some sort of ground-based interference.
How do you tell the difference between terrestrial and satellite signal?
SatNOGS automatically adjusts for the doppler shift in the frequency of a satellite so that if the satellite is being correctly tracked (and there are a few elements to this) then the signal being received should go straight down the waterfall….
Unlike normal SDR waterfalls, SatNOGS signals that don’t have doppler (ie terrestrial signals) will slope across the waterfall because the SatNOGS is shifting the frequency to compensate for doppler.
Basically your pass has sloping signals (and lots of them) and no signal straight down the waterfall, so no satellite signals are present.
All those terrestrial signals will be on all your waterfalls if they are constantly up. That will make it hard to decode signals so you should try to get rid of them. They are probably harmonics from some close digital signal (ie a monitor) or may be a switch mode power supply…try turning things off and see if they go away.
As for the decoded morse signals……The SatNOGS morse decoder only really works on good, solid signals. False signals are often detected as one of the following morse letters…E = dit, I = dit dit, T = dah and M = dah dah….
Out of interest, for the predicted signal to be accurately corrected for doppler shift it is important to have your location correct, to have the computer time correct, to have the most accurate TLE for the satellite…… Remember it is a prediction…not a tracked signal…if some of those are not correct you may have a hump/deviation in the straight signal in the water fall.
Hope this helps….
Regards,
John - VK4JBE
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Thank you, I have looked into the option of terrestrial noise, but this is consistent with all of the observations from my station. I even tried turning off my rotor and increasing my gain on my rtlsdr but it is present 24/7. Do you know of anything related to my setup that could be causing this?
At my QTH, I had horrible QRN. I turned off everything electrical until I finally found the culprit. It was my wi-fi router! Now, since I don’t need an internet connection whilst receiving a satellite signal, I power off my router for the duration of the reception.
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Unfortunately this is on the university campus and I am unable to go around turning things off to see what might be generating the sound. The antenna, however, is a cross yagi that is several feet above the roof of one of our buildings, and since it is directional I am unsure if this is being emitted by something terrestrial. The current thought that myteam has is that maybe this is something with our hardware.