Something odd started happening. I noticed that I saw a reduction in the number of aircraft being tracked. I looked at the gain and it was pegged. I thought a reboot would fix it (dip yesterday) but it seems to be doing it again.
Any thoughts?
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It seems you have automatic gain enabled.
That reacts to changes in the environment, maybe you have some kind of new interference in your surroundings?
You could set the gain to a fixed number, that would eliminate the change in gain.
What kind of SDR receiver are you using?
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Using the Flightaware SDR and a Flightaware 1090 band pass filter.
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That’s odd, the max gain for the FA SDR dongle is 49.8 and not 58.6 maybe your dongle is acting up.
Are you using the SD card image or the package addon for FA ?
They both need a different command to set the gain to fixed.
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Package add-on to base RP image
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For the package installation
sudo nano /etc/default/dump1090-fa
Scroll down and change these two lines
RECEIVER_GAIN=60 -> Change this figure to to the number you want, in your case 49.8
ADAPTIVE_DYNAMIC_RANGE=yes -> Change yes to no
then restart dump1090-fa
sudo systemctl restart dump1090-fa
Monitor for 24 hrs if your behavior is normal again. if it isn’t you might have a SDR dongle that is failing. The graph won’t show the value anymore since it is fixed.
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Thanks @tomvdhorst
I set it and restarted. Will monitor.
Changing the Adaptive Dynamic Range parameter to NO was the key for me! I have Tom to thank for that some many months ago. I expect a lot of users try to change their system gain only to have it revert back to the max because of that Dynamic Range feature they don’t know about and just give up in frustration.
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In addition to using default gain settings for some period, I have tried following two methods:
METHOD-1:
Made ADAPTIVE_DYNAMIC_RANGE=no and in RECEIVER_GAIN=60, changed 60 to 49.6 and watched for few days.
Next lowered 49.6 in steps of say 3 and for each step watched performance for at least a day, till I could find a value of gain which gave best performance.
METHOD-2:
(a) Left default settings as is (RECEIVER_GAIN=60 & ADAPTIVE_DYNAMIC_RANGE=yes).
(b) Changed ADAPTIVE_BURST= to ADAPTIVE_BURST=yes.
I have tried all three, i.e. Default setting, Method-1 and Method-2, The settings and results of Method-2 are given below.
For my location, I found METHOD-2 easiest and best suited, but this may not be true for other locations, as each location is peculiar.
METHOD-2 Settings
METHOD-2 Results:
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Thank you Toronto. Very nice detail. Do appreciate you sharing.
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Great stuff. Watching what method 2 is doing via “journalctl -f -u dump1090-fa.service”
Pretty interesting to see and I can see it is making a difference right away.
Thanks for posting
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abcd567,
Curious to know what would happen if I used your Method 2 configuration while I am running the modified Piaware Skyaware that has the title bar mod that allows me to Set the current gain from a pull-down menu selection of gain values? Would one override the other or butt heads?
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I was running that and I uninstalled it all…
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I have not tried this situation, but as far as I remember, when the blue button “Set Gain” is clicked, it does following 3 things:
(1) Changes value in setting:
RECEIVER_GAIN=xx
To:
RECEIVER_GAIN=yy
Where yy is the value selected in drop-down
(2) Changes setting
ADAPTIVE_DYNAMIC_RANGE=
OR
ADAPTIVE_DYNAMIC_RANGE=yes
To:
ADAPTIVE_DYNAMIC_RANGE=no
(3) Restarts dump1090-fa to implement above changes.
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Thanks. That sequence certainly does make sense.
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I’ve set some of my setups according to method 2 and will evaluate them during the upcoming week to see if they improve in regard to the fixed gain method 1 
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I will look forward to seeing what you find in your varied test bed of system antennas. Enjoy the rest of the weekend.
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Heck, I even constructed a new feeder site for this, site 16 is operational since an hour or so 
. That way I can compare it from scratch against another test setup . FA dongle, FA filter Bingfu 7 dBI antenna. When functioning properly I at least have an excuse for another Vinnant antenna 
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Maybe you have enough now to even qualify for some sort of farming tax exemption. Roger on the Vinnant excuse to present to the house manager. Maybe you have a birthday coming up and you can take the burden off of her by taking care of your gift in advance. It’s the courteous thing to do.
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Jumping in here, here’s what I get for gain if I set:
ADAPTIVE_DYNAMIC_RANGE=yes
ADAPTIVE_BURST=yes
It adjusts gain much lower (down to about 14 dB during the day) than when I used fixed gain (around 29.7 dB). This is with an RTL-SDR triple filtered LNA of 27 dB gain and an RTL-SDR V3 SDR dongle.
I don’t think this will produce better results on stats page “Aircraft Reported” and “Positions Reported” than what I was getting with fixed gain of 29.7 dB. We will see, today is a blue sky day so should have lots of GA aircraft out there.
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