I’ve recently installed a SatNOGS station Guatemala (first station in the country!) and am currently in the Testing phase. I am yet to improve the performance of my antenna, but have been able to receive faint signals from some birds.
I am noticing something slightly odd, that the frequency correction seems to be not exactly on point. Things I have checked:
Checked and double checked for correct Lat, Lon and Altitude configuration
SATNOGS_PPM_ERROR is set to 40 for my Nooelec NESDR Mini 2. I have used this value before for good performance.
Only thing I can think might be the problem, is that the PPM seems to vary depending on how long the RTL-SDR has been sampling. Say, if I just started sampling, PPM is about 36, and as time passes (and the SDR gets hotter) it stabilizes around 40. Could this be an issue?
This sounds like it should be your issue. Checking at the waterfalls the curve you see is typical to change of PPM and not a wrong location (since wrong location would produce a diverging and then converging signal)
I will look into it. Any good tools to determine PPM? I had measured it by hand with a HackRF transmitting with a very accurate TCXO, but that is no longer available to me.
Is the NooElec a TCXO version? If not, the crystal inside will drift with temperature over the course of an observation, and it will be difficult to correct for it.
I would strongly suggest using a SDR with a TCXO, as usuall you will only need to set the PPM once, and the temperature compensation bit of the crystal takes care of the rest…
No! It’s not. Ah, this makes so much sense. Hence why I had seen PPM would vary from 36 to 40 as I left the SDR running. Would adding a script prior to the observation that ‘pre heated’ the SDR work? Or just too much of a workaround?
