Observation 105306: FIRST-MOVE (39439)

Regarding Observation 105306

sometimes it’s difficult to tell, if there is a signal or not.
At aprox. 235sec. and 310sec. there seems to be valid signals?


FIRST-MOVE is a special case, you can check more about its history in an older discussion we had here.

Judging (and this is a great example why we need to have more than one station in one area) from this observation that was in parallel with yours, I’m 100% sure that both of the signals are from the satellite. Check the times:
starts at 2018-04-03 07:28:05
1st (audible) signal at 0:55 which means 2018-04-03 07:30:00
2nd (audible) signal at 1:55 which means 2018-04-03 07:31:00

105306 (yours):
starts at 2018-04-03 07:25:54
1st signal (on waterfall and slightly on audio spectrogram) at 4:06 which means 2018-04-03 07:30:00
2nd signal (on waterfall and a with slightly better view on audio spectrogram) at 5:06 which means 2018-04-03 07:31:00

Unfortunately your audio can not help here, the problem is that for cw decoder we have a narrow frequency bandwidth we use for audio and as you can see your signal is not exactly at 0 but a little (~ -1KHz) left. This can be fixed by tweaking the ppm parameter in satnogs-setup. Check this guide that describes the way to find ppm of your device.

Interestingly this observation which was also in parallel didn’t manage to get those two signals in waterfall but the first one (2018-04-03 07:30:00) can be heard in audio at 3:46 (you may need a good bass speaker). The pass was good but in this case ppm also needs adjustment.

Thank you for the informative reply.
I compared the signals,

Then i have downloaded the audio-file and opened it with baudline:


The RTL-stick has a 0.5ppm TXCO and i have checked it against different GSM transmitters with GitHub - steve-m/kalibrate-rtl: fork of http://thre.at/kalibrate/ for use with rtl-sdr devices. (0.9ppm)

I will try to tweak the ppm-parameter to 3ppm. This should give an offset of 1300Hz on 70cm.

To be honest, I have checked only this observation… maybe it is first move that drifts instead your sdr’s ppm error. Check also other observations, CW usually help more, to be sure.

PS I didn’t know about baudline, it seems to be a nice tool :slight_smile: