For the last year or so I have used a gain setting of 28, which seemed to strike a good balance for my setup. After upgrading to 6.1 and enabling the auto gain (with burst mode off), the gain has been set to MAX automatically ever since. My aircraft count went up and overall performance seems improved, but I have a concern about my message rate/aircraft. See graph below. Is that lower than normal? Possibly a result of the receiver being overloaded by a gain setting that’s too high?
How did it look like before?
The message rate is a simple calculation based on the current message rate and the number of aircraft.
MAX is not a typical automatic value, it should be a number. Please check with the following command if it is changing over the day:
sudo journalctl -xe|grep gain
You should get something similar like this:
Sep 09 20:06:20 Raspi3 dump1090-fa[18826]: adaptive: start periodic scan for acceptable dynamic range at increased gain
Sep 09 20:06:20 Raspi3 dump1090-fa[18826]: adaptive: changing gain from 49.6dB (step 28) to 58.6dB (step 29) because: periodic re-probing of dynamic range gain upper bound
Sep 09 20:06:20 Raspi3 dump1090-fa[18826]: rtlsdr: tuner gain set to about 58.6 dB (gain step 29) (tuner AGC enabled)
Sep 09 20:06:30 Raspi3 dump1090-fa[18826]: adaptive: changing gain from 58.6dB (step 29) to 49.6dB (step 28) because: probing dynamic range gain lower bound
Sep 09 20:06:30 Raspi3 dump1090-fa[18826]: rtlsdr: tuner gain set to 49.6 dB (gain step 28)
Sep 09 21:06:40 Raspi3 dump1090-fa[18826]: adaptive: start periodic scan for acceptable dynamic range at increased gain
Sep 09 21:06:40 Raspi3 dump1090-fa[18826]: adaptive: changing gain from 49.6dB (step 28) to 58.6dB (step 29) because: periodic re-probing of dynamic range gain upper bound
Sep 09 21:06:40 Raspi3 dump1090-fa[18826]: rtlsdr: tuner gain set to about 58.6 dB (gain step 29) (tuner AGC enabled)
Sep 09 21:06:50 Raspi3 dump1090-fa[18826]: adaptive: changing gain from 58.6dB (step 29) to 49.6dB (step 28) because: probing dynamic range gain lower bound
Sep 09 21:06:50 Raspi3 dump1090-fa[18826]: rtlsdr: tuner gain set to 49.6 dB (gain step 28)
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Running that command shows that the gain is varying between 29.7 and 32.8.
However when I run “piaware-config --show rtlsdr-gain” it says “MAX”.
I wish I could tell you what the message rate was before upgrading to 6.1, but I really can’t remember. My gut tells me it’s a little lower now though, which is why I asked.
The piaware-config setting does not reflect the gain used by adaptive gain
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