yeah, did think about that… will have to see how i can move it…
Thought I might be ok at 27cm
27 cm from the base is ok, it is the distance from the antenna top, detuning the top section due to the capacitance of the antenna to the metal. It drops the gain from that section somewhat. Worth a try to see if it adds some range to your reception.
I like your mounting system with the stick holding up the antenna. Must admit, it looks better than mine in the attic, and no pictures available. Hope this is a bit of fun improving your results.
Open file for editing
sudo nano /etc/default/dump1090-fa
Make settings as shown in red in screenshot below (change 60 in screenshot to desired value of gain)
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You might find the coverage better without the FA Filter, as the blue dongle already has the filter built in.
As has been discussed on numerous threads, the FA dongle’s filter isn’t ideal for many setups. Having the filter between the dongle and the antenna can help users in many instances.
Each situation is unique, so it may be valuable to test without it, but more than likely the filter will help eliminate noise that would interfere with decoding.
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I’m about 200m from a Cell mast, with a number more very nearby. The filter seems to have cut the noise.
I’m running it now for 24h to see if the number of flights I see has increased.
Then will start to tweak the range
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Dave, good idea to test for a while and only make one change at a time. Changing multiple things at a time, as many of us do, can easily take us down the wrong path. Your site is a bit more complicated than what most of us face with your interference sources. Nicely done.
After nearly 48h now the numbers looks stable. Few hours to go, but “seeing” the typical number I would expect for a Monday. However the “cheap stick” typically gave 40+ at over 150nm, now zero. But more local traffic…
From my understanding I need as larger gap between the 2 lines in the signal level.
Others in similar locations seem to be able to get -1 to -34dbm
I’m between 0 and -15dbm, aiming for distance, where should aiming? less gain?
After cutting noise by adding a filter, higher gain results in larger disdance.
So the distance between the 2 lines is allow reception of the weaker lower power signals.
But the tuner is then overloaded with string local.
I’m amazed how much my cheap DVB setup performed!
@abcd567 i noticed in the screenshot you shared the inital gain is 60. Is that not beyond the max?
Also the adaptive max/min would the max value support -10
The tuner chip of dongle is designed for TV signal which is different for different tv stations, but it remains constant for each tv station. The AGC therefore adjust the value of gain according to signal level of the station tuned.
The ads-b signal is a mixture of signals from various aircraft and is continously varying in strength due to different aircraft at different distance, and hence different signal level. This continously varying signal drives the AGC crazy, and it rises beyond normal max of 49.6 and gets stuck at about 60 dB.
The setting 60 is same as -10 or AGC.
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Have you tried running the new setup with the extra filter off to see if that improves your range?
hi @gavin323
A second filter?
What im going to try is adding a length of cable like in your setup maybe around 1m see what that does. Read some people saying that around 18" seem to improve it… Worth a try, and you can see in the old rig, there was a cable and it was a much greater range…
Any source of interferance was there before, so should be there now. The only new one is a flight stick, preciously this was around 1m from the antenna base, now its much closer… This will have to wait a week.
Also going to try producing the chart that graphs the interface, see if im still getting noise form somewhere…
Still cant seem to get any distance betwen these:
Trying various gains.
thanks
What I am having trouble understanding is that your noise line is consistently above your weakest signal line. Mine is the opposite, and it seems like it has been opposite on just about every other user’s graph I have seen.
I don’t know, but I think it might be related to your dynamic range being so narrow.
It seems like the gap between your strongest and weakest signals stays almost the same when you change your gain - the whole graph just moves up or down. That behavior is inconsistent with my experience.
I noticed in one of your photos that your USB dongle is attached to a USB extension cable - how long is that cable, (and how far to the pi?). If it’s a long cable (especially if it’s a 5 meter or longer), that could pick up interference from within your house. And the coil you have there makes it look neater, but could also be creating inductance problems (it could be amplifying noise). Assuming you have the Pi elsewhere, could you temporarily move it to be close to your dongle? Maybe run an extension cord temporarily for power?
I also recognize how frustrating this must be - you had a system that was operating decently, spent money to “improve” it - and made it worse! And now you have a bunch of people saying “change this, change that” and you are spending more money to try to get back to where you were.
It’s kind of the nature of the beast though. I started out with the FA pro stick, a Pi 3B+ and one of those little magnetic whip antennas that isn’t really for ADSB. It worked ok, but I felt like I could get more.
After doing some reading here, I reduced the length of the whip to 1/4 wave (53mm?). That helped but not enough. Added a cheapo LNA from Amazon. Definitely made things worse at first. A lot worse. Had to reduce the gain on my pro stick at TON - down to 30-something. That again was better, but still not great. Then I added the FA filter. I tried it both before and after the amplifier and found that I got the best results after. But then I had to increase my gain again to compensate for the filter.
I let that go for a year or so, and then added the FA antenna (hangin indoors) - and again, my initial results were worse. I had to turn the gain down again.
Eventually, I moved the antenna to a satellite dish mount at the peak of my roof (2 story). Needed 15 meters of antenna cable to reach the Pi in my garage. This (again) initially made my reception worse. I had to reduce gain yet again once the antenna was free of all of the obstructions in my house.
It now has sat comfortably with a gain of 22.7(?) for about 3 years. My location is about 20 miles north of Portland, Oregon, and I regularly pick up aircraft from the Canadian Border to the California border.
Point of all of that being, nearly every change (especially hardware changes) can affect the whole signal chain. And since everyone’s environment is different, it can take some trial & error to find the best results for your particular situation.
Have you done a “hey what’s that” plot to get an idea of your theoretical range? It’s a good starting place as long as you don’t treat it as gospel. You can’t see planes in places that they ain’t. Using my case for an example (again), HWT says that I should be able to see planes at 30,000 feet out to 100 miles over the Pacific Ocean. Problem is - planes don’t fly there. The flights going from Seattle to Hawaii are already more than 100 miles offshore by the time they get west of me - though I do see them leaving Seattle, and the great circle flights from SFO, LAX, and MEX to and from Asia stick closer to the coast, usually around 25 to 50 miles. So I could see planes if they were there, they just aren’t there.
Evening all,
So some progress tonight…
@fhmiii moving the antenna away form the plate is hard, loft if 500mm deep in loft insulation. I squeeze the latter through the hatch and literally have to go up only, i cant move easily in other directions, but its noted and its on the to do list, but keep reading… 
@abcd567 again thanks for the advice, I was about to make this change at the weekend, but again, keep reading
Many thanks to @jafrank seem you have cracked it… 
I took the pi, reenabled Wi-Fi, and connected it to a 2amp socket on a decent power bank, connecting the Pi directly to the receiver, then moved it all in to the loft…
The result was almost instant, despite there been little traffic here at this time of night, I hit nearly 160nm nearly instantly.
The Aircraft Seen with Positions rocketed up, ones without also fell. This is the first time the with position was higher than without…
The noise floor on the charts fell below the weakest signals… down from -12, to -24
Looking in Virtual radar, all except 2 flight had speed and route etc… (2/19)
As and experiment, I added in a 3m USB lead, it cut the flights from 19 to 8 …
This was all in about 20min…
Thankyou! for all that have contributed towards this, but seem noise on the USB lead appeared to be root of my issues…
As for what’s next:
I plan to split the PI… Have the Pi4 running PiHole and other apps located next to the router.
I will reinstall my Raspberry Pi 2 Model B which was running FA until about 3 weeks a go, but i can be dedicated to FA now…
I have power close by in the loft, and will use a decent google PSU. but the PI will now be directly connected to the receiver.
Hopefully that should give much better results…
Have I missed anything?
Wont be able to swap the equipment until the weekend.
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Wow, that’s great! Thanks for the update!
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Perhaps try it with a Pi? 
Is the ferrite on the data cable or power cable?
Many people see a performance drop when using a USB cable between the Pi and the dongle (not all cables are equal). Try different cables or no cable at all.
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