Drop down selection list maybe?
2 Likes
Thanks @wiedehopf for your graphs1090 project. I installed it for the first time last night and it’s very slick. You are a coding god. I’d been playing with gain settings so was curious to see if the graphs could tell me anything I should care about. They appear to confirm that using the FA antenna with gain set to max does well, and that adding in the Uputronics SAW filtered preamp and dropping the gain to 49.6 does even better, giving a bit of additional range without compromising anything close up. Tracks with single message increases a fraction with the preamp, as do signals stronger than 3dBFS.
Dropping the gain to 48.0 doesn’t change anything except makes the furthest signals a bit weaker, so I can only imagine that would eliminate the very weakest signals and so is not desirable. So I’ve stuck with 49.6. It’s a blue Pro Stick Plus.
I’d already gleaned the same conclusions from looking at the RSSI numbers live (similar to the way @abcd567 described) but the graphs are useful to confirm. That said I’m always open to interpretations I’ve not considered. The biggest difference I can make here is to get the antenna up on the roof and start over with readings but that’s going to have to wait a while.
The graph before the gap around ~1400 is the FA antenna with gain on max. After the gap is adding in the preamp and gain reduced to 49.6.
As stated initially in this thread by wiedehopf you should aim for a value of 5% or lower for the message > -3dBFS as long as you are not located close to an airport with lots of local traffic.
This seem to be to high on your device. I would try with a lower gain of 44.5 or 42.1 as a starting point and then monitor it for a while.
I am using also the blue Pro-Plus Stick with an optimized outdoor-antenna but without additional amp.
my gain is currently at 40, everthing higher returns a higher strong message rate and as a consequence a lower message rate.
There is also no range increase notified.
That’s a bad assumption.
It assumes you aren’t already resolving the noise floor with the ADC.
Generally rtl-sdr dongles won’t usually drop a signals stronger than -30 dB.
See if you lose any range taking your weakest signal to that point.
This might be an extreme to go to, but not decreasing gain means that you will lose close by aircraft.
And local aircraft can be most interesting, helicopters or small planes flying by.
Replying to both @foxhunter and @wiedehopf.
I’m not new to playing with the gain – see the gainmap thread, for example. I’ve done plenty of experiments with this configuration over the last 18 months and in all of them I get maximum range and aircraft (using a range plot over the course of a week) with gain at 49.6. Going higher to max decreases these, as does going to 48.0 and below. I’ve not yet encountered a situation where aircraft a few hundred ft overhead nor those at the airport a few miles away are unresolvable. There are plenty of interesting aircraft passing nearby.
If I remove the preamp then range decreases. If I then increase the gain to max, range increases but not as much as with the preamp at 49.6. I suspect the antenna being indoors is acting as suitable attenuation of what could otherwise be very strong signals, allowing me to get away with a higher gain for the fainter in-band signals from distant aircraft. These are passing through the filtered preamp and filtered Pro Stick Plus, with nearby GSM 900 and radio being suitably killed. When this antenna goes on the roof it will be a different story and I suspect that it will be advantageous to drop the gain a few notches as it will have a clear view of the sky and around 300ft AGL at the airport.
Putting it together, my own analysis of the graphs is confirming what I already knew. It always very much depends on the physical setup of the site; assumptions can’t easily be made. The -3 dBFS figure is a useful metric but it’s not an absolute limit to lose sleep over. And I can see that number by eyeballing the RSSI column anyway. I was curious to see if the graphs help to visualise any additional info but it looks like the same info presented very nicely. The system graphs will be useful if the RPi ends up in a less accessible place.
Thanks again.
1 Like
I’d be surprised if going to 48 measurably decresases anything over a longer period of time.
But maybe it does.
As you already have quite a few aircraft at a somewhat constant distance, the statistics change and near an airport a larger percentage is quite normal without being an issue.
I’ve noticed that with the gain at 42.1 I get aircraft at the view limit at RSSI around -18, which is okay, and I also get occasional aircraft listed at -49.5 RSSI, which is an anomaly. If I increase the gain to 43.9 and above I never see that anomaly so that’s the lowest I’ll go at this site as it stands.
I’m re-imaging the card shortly to get back to a clean setup. I’m going to leave the gain at 43.9 for a week and see how that pans out in terms of range and aircraft.
That’s just anonymous MLAT results from FA, nothing to do with actual reception.
Anyhow, experimentation and knowing what your focus lies on is key.
So in the end, whatever works for you 
@davlinds
What is the output for this command:
sudo apt update
sudo apt install git
The note from @obj implies that reception is relevant to seeing these. Although, since there will always be aircraft on the edge of reception which could trigger this effect regardless of any gain setting, on reflection I probably shouldn’t infer any correlation between lower gain settings and this anomaly regardless of what I’ve experienced.
I haven’t read the note, but with 99% certainty you have misunderstood it.
-49.5 has nothing to do with a real signal, ever.
You could have perfect -5 dBFS reception of a plane, but the corresponding anonymized MLAT plane will have -49.5, otherwise it would be less anonymized wouldn’t it, as you could match the RSSI to an actual ModeS plane you are tracking.
With an airport close by i’m not saying that you should have 1% strong signals, but at least the 2nd half of the graph seemed excessive.
Please do. I’m afraid we’re at crossed purposes here and you’re trying to correct me on something that I’m not saying. I know that -49.5 is a synthetic MLAT signal. It’s the aircraft’s movement out of a reception area, which is proportional to real signals, which can momentarily trigger its display in SkyAware, hence the correlation.
Which note are you even referring to?
I don’t understand what you are saying.
Trigger what display?
Sorry I posted this in the wrong group initially.
I have a Pi 3b supplying FA and ADSBEx and running stretch.I have tried to load the performance graphs but I get error message “Failed to install required packages git python rrdtool collectd-core”
That’s strange as I have git and python installed, but cannot find rrdtool collectd-core using apt-get.
Any pointers please
git is already the newest version
Well then
sudo apt install python rrdtool collectd-core
cat /etc/os-release
sudo apt install python rrdtool collectd-core
Package rrdtool is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package ‘rrdtool’ has no installation candidate
E: Unable to locate package collectd-core
pi@piaware:~ $ cat /etc/os-release
PRETTY_NAME=“Raspbian GNU/Linux 9 (stretch)”
NAME=“Raspbian GNU/Linux”
VERSION_ID=“9”
VERSION=“9 (stretch)”
ID=raspbian
ID_LIKE=debian…
What is this … ?
Let’s see …
cat /etc/apt/sources.list
apt show collectd
apt show collectd-core
I’m really not sure what’s happening, let’s try the official Raspbian mirrors, use this command:
sudo sed -i -e 's?http://flightaware.com/mirror/raspbian/raspbian/?http://mirrordirector.raspbian.org/raspbian/?' /etc/apt/sources.list
Then, let’s try again …
sudo apt update
sudo apt install python rrdtool collectd-core
cat /etc/apt/sources.list
#deb http://flightaware.com/mirror/raspbian/raspbian/ stretch main contrib non-free rpi
# Uncomment line below then ‘apt-get update’ to enable ‘apt-get source’
deb-src Index of /raspbian stretch main contrib non-free rpi
apt show collectd
N: Unable to locate package collectd
N: Unable to locate package collectd
E: No packages found
apt show collectd-core
N: Unable to locate package collectd-core
N: Unable to locate package collectd-core
E: No packages found
sudo sed -i -e ‘s?http://flightaware.com/mirror/raspbian/raspbian/?http://mirrordirector.raspbian.org/raspbian/?’ /etc/apt/sources.list
sudo apt update
Get:1 Index of /raspbian stretch InRelease [15.0 kB]
Hit:2 http://linux.teamviewer.com/deb stable InRelease
Hit:3 http://flightaware.com/adsb/piaware/files/packages stretch InRelease
Get:4 http://flightaware.com/mirror/raspberrypi/debian stretch InRelease [25.4 kB]
Get:5 Index of /raspbian stretch/main Sources [9,721 kB]
Fetched 9,761 kB in 10s (903 kB/s)
Reading package lists… Done
Building dependency tree
Reading state information… Done
7 packages can be upgraded. Run ‘apt list --upgradable’ to see them.
apt list --upgradable
Listing… Done
beast-splitter/unknown 3.8.0~bpo9+1 armhf [upgradable from: 3.7.2]
dump1090-fa/unknown 3.8.0~bpo9+1 armhf [upgradable from: 3.7.2]
piaware/unknown 3.8.0~bpo9+1 armhf [upgradable from: 3.7.2]
piaware-repository/unknown 3.8.0~bpo9+1 all [upgradable from: 3.7.2]
piaware-support/unknown 3.8.0~bpo9+1 all [upgradable from: 3.7.2]
piaware-web/unknown 3.8.0~bpo9+1 all [upgradable from: 3.6.3]
teamviewer-host/stable 15.1.3937 armhf [upgradable from: 14.7.1965]
sudo apt install python rrdtool collectd-core
Reading package lists… Done
Building dependency tree
Reading state information… Done
Package rrdtool is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package ‘rrdtool’ has no installation candidate
E: Unable to locate package collectd-core
Not good news. I am not looking forward to building the packages from scratch (if I knew what to do anyway)
I’d suggest going to Raspbian Buster, seems there is an issue with the Stretch repository.
You can just re-image with the new 3.8.0 piaware sd-card.
But let’s check if the sources actually changed or i messed up the sed command:
cat /etc/apt/sources.list
Did you type or copy paste this command?