Observation 1215443: FOX-1C (43770)

Regarding Observation 1215443

Hmm, Oddly turning up SATNOGS_RF_GAIN seems to have an inverse effect?

When I turned it up as high as 48.0 on previous passes, the satellite signal mostly was gone, but now just before this pass I turned it back down to 33.8 (which is where it was on other successful observations) and the satellite signal is received.

I’ll play around to find the sweet spot.

73, Glenn, KJ7SU

Most likely when it was at 48.0 the SDR got overloaded and the signal was just lost in noise. :slight_smile:

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Keep in mind that at some point, turning the RF gain any higher will not have a positive impact on the signal-to-noise ratio (S/N). Beyond that point, increasing the RF gain may seem like the signal is increasing, but the noise floor is also increasing, possibly at a greater rate, ultimately degrading your S/N.

In order to find the “sweet spot” that you have in mind, you should turn the gain all the way down to 0 dB and tune to a source like an FM radio station (depending on your antenna’s designed frequency and environment, you can pick another source as long as the transmission power is relatively stable). As you increase the RF gain slowly, your S/N should increase, but around ~8 dB* (for RTLs), you will notice that the S/N stays the same (noise floor increases with signal).

This is the value your RF gain should be set to for optimal results (maybe slightly higher to ensure you haven’t underestimated the value of the “sweet spot”).

*This value varies from system to system, so experiment as instructed above.


Yes, likely. Thanks for the reply.

73, Glenn, KJ7SU

Thanks for the good advice on this. I will approach it with a strategy like this.

Kind regards,
73, Glenn, KJ7SU