Regarding Observation 12832288 …
Does this look like a valid signal? What can I do with it now?
Hi, unfortunately, this is local noise. The signal appears to go from a lower to a higher frequency, because the sdr is tuned to compensate for the expected Doppler. You should expect signals to be a straight line. Like your earlier successful obs:
I noticed from the Metadata that the gain was 28 previously and is now set to 0.9. I don’t know your serup but if it is just an antenna and rtl-sdr, then you can set the gain to about the maximum, like 49.6. If you use an LNA, then something like 20 is probably a good start.
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Thank you for your feedback. I followed the guide to find the right gain with GQRX. We added a LNA to the antenna box outside and if I set the gain higher the 1 the noise floor in GQRX will start to raise. I’ll try 20 now.
We changed the Gain to 20 and did a 3 hour autoschedule window with matching AZ und EL limits for the trees and houses.
And you didn’t receive anything yet?
How is the LNA powered? Is it possible that it is off? Do you need to turn on the Bias T of the rtl-sdr?
unfortunately not. The LNA is powered by a external Bias-T injector as our Nooelec does not have a Bias-T. We checked the power with openwebrx and gqrx. If we turn the power off and set a gain of e.g. 27 we have local radio signals in 2m and 70cm. If we then power the LNA using the Bias-T the noise floor raises a lot so we can set the gain in openwebrx to 0 to 3 to get very good results in FM, AM and DMR local radio. So I assume that the LNA works. But unfortunately no success by now with satnogs client
But this one is a good one:
SatNOGS Network - Observation 12832608
Basically it works!
Maybe I was wrong with my general advice. You appear to have a lot of gain in the lna and antenna. Maybe the lower gain settings are better. And the higher settings are overloading the sdr.
Nice one!
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By the way take also a look on this guide Operation - SatNOGS Wiki that will give you an idea to check what is and what is not a satellite signal.
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Thank you very much. Now I understand that I don’t have to check all the passes. There are some that are clearly good. But I only see them if I’m specifically looking for them. Only the ones that aren’t clear are submitted for review. I’ve now set the gain to 8.7 and will test again. I’m also trying to adjust the AZ limits again so that passes that start completely behind the house aren’t scheduled. My desktop rotator is very helpful in determining whether a pass is behind the house or behind the trees. In six months, I might have a better position for the antennas with less obstruction.
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Seems like 2m band is working much better then 70cm. Maybe the QFH is not the best idea? I rechecked 70cm with openwebrx. If I set the gain to 0.9 in openwebrx I have dark red to black signal strength in waterfall in openwebrx during signal reception. I can successful receive DMR and FM radio. If I set the gain to 2.7 or 3.4 the waterfall turns light green to orange and the quality of the local radio reception decreases. I don’t really understand why the 70cm satellites do not even show anything in the waterfall.
@tomte76 One observation that may be useful in setting gains appropiately is: 1) SatNOGS uses a GNURadio framework for the rxer; ) GQRX also uses the GNURadio framework for its rxer; 3) OpenWebRX uses a DSP library called CSDR (Complex SDR) for its receiver.
I always use GQRX to get the gain based on the noise floor rise because it uses the same GNURadio framework as the SatNOGS client. I love OpenWebRX, but it is different, so I don’t use it for SatNOGS calibration purposes.
Hope this helps.
John VK4JBE
