What is a "good" observation?

Using my temporary vertical antenna, I have observed several satellites. Subjectively, they look “good,” that is, I see a signal that looks like CW and has the expected Doppler shift as it transits. However, SNR is not yet good enough to get decodes. Do I mark these as “good” and put my system into production, or wait until I have a high gain antenna on the automatic rotor and getting decodes?

Well as long as the signal is in the water fall it’s good. :slight_smile:

OK, cool. Now, I’m looking at the screen for scheduling observations. I see that a satellite pass I have scheduled shows an overlap percentage. In many cases, it shows “100% overlap” with another satellite pass, even though their transit times do not actually overlap. Does this overlap take into account the time it takes my RPi to process and send the data? (Therefore it can’t do another observation while it is still busy with the previous one?) … is that what that means? Or?

Not sure. I know if it says 100% either it’s already scheduled or its over leaping with one close. (Like above or below) this is scheduled.

Might want to wait for a better answer from someone else tho. I am still sort of new even after having a station online for over a year or so.

If your station is set up properly (lat/long) and the keps are good, you shouldn’t “see” any doppler shift, as the client adjusts for that to keep the received frequency in the middle of the waterfall. Can you provide a link to an observation where you see this?

Here are a couple of my observations, hopefully others can see them…



Are the signals supposed to go straight down the middle of the waterfall? I’m pretty sure I put lat-long of my station in right, at least, I think so. I’m thinking the keps are supplied by the SatNOGS network, so I wonder if there is something else going wrong somewhere…

With further research, I see that the curvy lines on the plots are terrestrial signals (“birdies” I guess) - so probably my vertical antenna (temporary) isn’t able to pick up enough of the satellite signal to detect it. This will be corrected when I put the yagi on the rotator.

Another thing I noticed in one of the measurements (see observation https://network.satnogs.org/observations/543674/ ) - there is a faint straight but fuzzy line in the middle at 0H offset; this might be a satellite signal, as it has no drift.

So I’ve gone and vetted the observations you linked above the way I would vet them on my station.

You are correct in that signals from the observed satellites will show up as a vertical line down the waterfall display. If it varies from that (i.e. appears to have a doppler shift) then its likely local interference. There is an observation vetting guide here: https://wiki.satnogs.org/Operation

I think your station is probably not performing as well as it should be. CAS-4A usually provides excellent signals - see a recent observation from my Turnstile station (Wimo TA-1) for example: https://network.satnogs.org/observations/535996/

If you are using a vertical antenna, you are going to have an null directly above your station, and depending on the gain of the antenna, reduced performance pretty much everywhere above the horizon. You may be able to receive some signals from lower-elevation passes, but at the same time your antenna is also picking up noise from around your station, lowering the SNR of the observation.

I’d probably suggest either using a turnstile, or waiting until you have a functioning rotator system before putting the station properly online.


From my experience with my vertical antenna I can say it should work pretty well. And oddly there isn’t as much of a null directly above as you would think. May just be my vertical tho.

That first observation you can clearly see the CW as a faint vertical line in the center of the waterfall. But keep in mind, the only signals that will look like vertical lines will be CW or other continuous tones. Most signals will appear as stacked horizontal lines, centered in the waterfall (left to right). These stacked lines are usually telemetry packets, but can also be APRS messages, etc. However some other satellites (especially those with voice) will carry more recognizable signals (such as SSB qso’s on the linear amateur satellites, and FM qso’s on SO-50). And other satellites have a whole bunch of stuff going on (the Fox satellites look like two CW lines, with FM plastered over the top - the “cw” lines being the DUV telemetry that is “hidden” underneath the voice QSO’s).


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I’m pretty sure my current (temporary) antenna is indeed not performing all that well; I just connected the SDR to a vertical I have for using local repeaters, which is close to the ground and behind my house. I just wanted to see if I could collect anything at all, and it seems to do that. I have a working SatNOGS rotator (which delightfully tracks satellite passes while sitting on the workbench) on which I am going to mount a Yagi; this will get some good signals.


My personal experience:
I spent many hours trying to decode something with an rtlsdr dongle and a diamond X300 vertical collinear antenna.
I didn’t decode anything until I decided to build a turnstile antenna.
My 2 cents
Alfredo IZ7BOJ