Buy RTL-SDR Dongles (RTL2832U) used to sell metal cases for the dongle that fit the FA models(I bought a few years ago). They were good for shielding them from some interference. Not sure if anyone else sells them.
Might help us all here if you could tell us what your current gain setting is at. As jafrank wrote above at the end of his comment, the current gain can probably be increased somewhat.
As the commenters mentioned, we often use the Signal Level chart to adjust the gain setting, while ensuring the Message Rate chart red portion stays below 5%. This is all part of working out how to get our best performance, and we have all had to do this when we were learning too. The Signal Level blue line can get up higher near the 0 level to help with your range. Change the gain up by 5db at a time, and see how the graphs preform. It will take a few changes to hone in on the best settings for your system.
Every location and system is different and you do have some interference located nearby. You got this, and understanding the problems are more than half of the battle.
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For comparison, this is my signal level graph, set to the 2-hour view like you have in your screenshot. The dark blue line near the top represents my strongest signals. You want that up in the -1 to -2 or so range, as far as I can tell.
The green line at the bottom represents “noise level”, though I think I recall reading that the name isn’t strictly technically accurate. The light blue line above that shows my weakest signals.
I’m definitely not a radio engineer, but my understanding is that in most cases you want as much space as possible between those two blue lines. That space represents your dynamic range - the strongest and weakest signals you can pull in.
I find it more helpful to look at longer time frames. Two hours is really too violatile to glean useful results from. I like to use the 7 day or 14 day views to better understand my performance - though the shorter views can help when making changes.
7 day view:
Morning… Thanks again for the reply…
Current gain it set to 20.7… Running dump1090-mutability i think i can go up to 22.9 or down to 19.7…
Happy to go down the filter route is needed.
Thanks, those are helpful. I dont have anywhere near that gap…
here is the latest this morning:
2h
8h
thanks
@DaveSaunders
A filter may further improve the range.
My experience is that when I added FA filter when I switched from Cantenna to FA antenna, everything else remaining same, my range and message rate dropped to nearly zero. At first I thought it is bad N-to F connector, and ordered another costlier one, but that did not make any difference. Lowering gain also did not help much. Finally I suspected it may be strong RF noise, and ordered FA Filter. When I added FA filter, my reception improved dramatically, much better than Cantenna.
I have FA Filter, and dont need another filter. However just to test a low-cost LNA+Filter from China/Aliexpress, ordered one. Still awaitig delivery.
I do NOT recommend you to order this Chinese/Aliexpress LNA+Filter, as it is untested yet. However I do recommend Flightaware Filter which has been tested and proven very good by me as well as by a very large number of other users
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In Europe, all the mobile frequencies are not filtered out by standard FA Band Pass Signal Filter, Dual 978-1090 MHz (Light Blue)
Users in Europe require FA Band Pass Signal Filter, 1090 MHz only (Dark Blue)
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AGC will not work if you want to track aircraft. It would work if you would use it as DVB-T stick. That explains the large red area in graphs1090
Adjust gain accordingly. It’s mainly a try and error. You should start with 49.6 and then go down stepwise, leave it running for an hour and check again. Make sure to test it during day where most of the aircraft are around.
Make sure to restart the dump1090 service any time you change the gain, otherwise the service won’t recognize the config change.
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thanks @abcd567 i took the advice hand have gone for a filter…
Gone for the FlightAware Dark Blue Filter…
In for a penny, in for a pound… 
Now really have to make this better than my last DIY setup
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thanks @foxhunter I started in the middle and moving up…
Here is my result after 24h, signal level looks to be going in the right direction…
At the end of my config file, I have the following
ADAPTIVE_DYNAMIC_RANGE=yes
adaptive-burst yes
adaptive-burst-alpha=0.3333
Which gives me the following stats
thanks…
See ur gain is pretty much maxed out…
Hope the filter on order will help…
I don’t know what a “mini-SMA” is, but could you post a pic of it (showing the centre connector) please?
Flightaware Antenna Indoor near window glass → 1 meter RG174 coax → FA Filter → FA ProStick Plus (Blue) → OrangePiPC → Armbian Bookworm → dump1090-fa
Graphs below show the drop in reception when external FA Filter was removed from above setup
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Evening all,
@abcd567 thanks for the charts i will take a more detailed look shortly…
My filter arrived this afternoon, so quickly installed it… I had moved the gain back to max before installing as i figured id need to restart the tuning process so thought id start at the top…
The first line is the filter going in and the second is me starting to cut the gain…
2h average of strong message is 5.00% but i think i still need to go lower… My signal level is very high and narrow, if i understand that correctly i need this as wide as possible
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Tonight I have replaced dump1090-mutability with dump1090-fa…
Left Autogain enabled, see if that improves my situation…
I have noticed a massive reduction in CPU!
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Ok, so think I have started to make some progress since starting over…
CPU usage was a surprise since moving to FA…
Here is the setup:
Antenna > FA Filter > FA Pro Stick > USB with ferrite choke > 3Amp Apple USB-C PSU
With the following set:
ADAPTIVE_DYNAMIC_RANGE=yes
adaptive-burst yes
Im starting to see consistent results:
The range is still much smaller than the cheap stick, but I’m tempted to give it a bit more time…
The Auto Range seems to help…
Where do you specifically set gain in dump1090-fa?
Thanks
Check this post for adapting gain settings:
Basicly you can define the upper and lower limit in order to keep the changes inside a predefined range.
Other option is to disable autogain and to set it manually
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Good picture in your attic. One suggestion, perhaps move the antenna away from the metal rafter reinforcement. That will affect how the antenna performs. Half way between the joists will help. I have the same problem in my attic too.