Make sure to evaluate per 24 hrs and not based on a few or single steps. Traffic varies during the day and you want to get to an optimum based on a daily average.
1 Like
Perfect. Got another 12 hours. Will look at it tonight and adjust. Thanks for explaining all this above. I’m sure it’s not the first time you’ve explained this.
I think 12.5 is about right for you.yesterday you had 35%, last 48 hrs show 19 %. So Ithink keeping it on 12.5 for 48 hrs will bring you around 10-12 % of strong messages without sacrificing range or positions.
I have to agree with turning down the gain. For a receiving antenna, the way I look at gain, is like an aperture on a camera. The higher the gain the more wide open the aperture, which will increase your noise floor and possibly drown out signals. So while turning down the gain may not allow for you to receive everything, it should allow for less noise and clearer signals. It’s just tweaking it to find that sweet spot your happy with.
2 Likes
going to hijack this thread here, if you all don’t mind.
@tomvdhorst I’ve run graphs1090 for 24 hours on my 2 identical setups. One has 12.2%, the other 14.7% over 24 hours.
I have pretty decent range/# of aircraft as far as I can tell given that my antenna are outside but don’t have an unobstructed view of the sky and where I live is very, very hilly.
Both have gains of 42.1 which barely budge throughout the day with the automatic gain script.
any reason to play with lowering the gain a tiny bit? I know you said 5% is a good target, but unlike @Iemand91 I’m not starting off at 99.9%…
here’s one of them (the slightly less well performing one)
You could decrease one step to 40, your weakest signal is around -25.6 now and that could be -30 on average.
So set autogain to no and set the value to 40.
Let it run for 24 hrs and see if it improves the lowest signals. If that isn’t the case you can enable autogain again.
2 Likes
Your reported noise floor is quite high and consistently above your weakest signals. I think your first order of business is to invert that scenario which is done by reducing the gain. You probably need to go down several steps and try to get the noise at around -30 for a starting point. As @tomvdhorst said ditch the adaptive dynamic range function and start setting the gain manually.
2 Likes
Sorry to hijack, but how do you guys get those performance graphs, and how do I get to a place that I can set the gain manually? I don’t see those options in settings when I login to flightaware through chrome.
Do I have to pull the SD card from the Raspberry or can I somehow make these changes remotely?
There are some very useful addons by @wiedehopf located here. Graphs1090 and Tar1090 are must haves. They are installed at your ads-b installation be it a Raspberry Pi, a PC or another computer.
1 Like
very helpful. thank you.
I set both of my setups to 37.2 and will let it run 24+ hours and see what happens. Definitely want the noise below the weakest signal. I can see during quieter times the gain turns down and and this is exactly what happens.
I appreciate everyone letter me hijack into a “can you help me tweak my settings to get better pickup” therad.
My current situation for the last 24 hours (gain unchanged at 12.5):
The last 7 days. Last Saturday afternoon, I placed the FA filter:
There are 2 interruptions visible on Saturday; that’s when I did the frequency scan as described here:
First without the FA filter:
Then with:
Filter doesn’t seem to do thát much, however Message Rate does seem to be slightly better.
And now my current setup:
The newer (dark blue) FA filter is supposed to be an upgrade (better attenuation of 950 MHz) but honestly; my problems are gone, receptions is okay and I’m not feeling like spending more money for (maybe) slightly better results.
Maybe tweaking gain here and there but that’s about it I think.
I’m just content my setup if fully functional again.
2 Likes
Have fun with your gear again, if you need assistance just let us know 
This looks so much better. Congratulations!
The noise line displayed is not really noise.
Undecoded (parity error / similar) messages will count as noise while actually being signal.
Pretty sure ppl are used to one sender one receiver typical radio link. With multiple senders of all kinds of signal strength it becomes super complicated distinguishing noise and signal.
1 Like
It would seem you have great range. This usually means you become severely limited by the dynamic range of the rtl-sdr.
If you’re missing low flying close by flights on your display, reduce gain.
It might reduce range but that’s the tradeoff once you are limited by dynamic range.
If you’re super serious you could go and upgrade to an airspy mini + uputronics LNA.
Improved dynamic range and all that. (from the airspy … which then requires an LNA because it’s not sensitive enough for peak performance without it)
1 Like
Thanks. Yeah, range seems to be fine; looking at the range rings I’m probably at my max (sometimes over maximum theoretical range, sometimes within).
Will try some lower gain to see results.
New equipment is indeed nice, but I think I’m not thát serious. 
As it is now, I think I have a nice, decent system running, and much better than it was before.
No part of your antenna should be adjacent to the mounting mast pole. Raise the antenna mount to the very top of your mast pole. The antenna needs to stand alone relative to the mast pole to work properly.
Well, for sure if the mast pole is metal. But if the mast pole is a PVC pipe, I wouldn’t think it would matter that much. After all, the antenna itself is already in a protective radome (of possibly PVC material).
I would be curious to see what the antenna swr profile looks like with a SWR meter connected up to it in that overlap configuration.