To conduct the two scans, dump1090-fa on RPi was stopped to make the dongle available to scanning software “Spektrum”. During both scans (with & without Filtered LNA) the gain was set through the Spektrum.
After finishing scan, I stopped “Spektrum”, and rebooted Pi. This resulted in that dump1090-fa started and grabbed the dongle. As the dump1090-fa setting was ADAPTIVE_DYNAMIC_RANGE=yes, the gain was automatically set to 49.6 by dump1090-fa for both cases (with & without Filtered LNA).
I did not try to manually drop the gain to 33 in case of Filtered LNA.
I have now repeated the performance test, this time making ADAPTIVE_DYNAMIC_RANGE=no and manually setting RECEIVER_GAIN to 49.6 (in case of without Filtered LNA) and 33 (in case of with filtered LNA). Followings are the results:
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Screenshot 1 of 2:
Antenna > Generic DVB-T (Black) > RPi Model 4
Gain = 49.6
Total Aircraft: 36
ADS-B Message Rate: 195.8/sec
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Screenshot 2 of 2:
Antenna > LNA+Filter > Generic DVB-T (Black) > RPi Model 4
Gain = 33
Total Aircraft: 80
ADS-B Message Rate: 263.0/sec
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