Yep nearby stats are the median values of the last week. The 30 day stats shown for each receiver not averages, but daily. They aren’t the best way to measure receiver performance however. The number of aircraft is a count of unique icao addresses seen during that day, whether you received 100 messages from it or 100,000. The positions reported is also not really a reliable measure either since it is a count of positions uploaded to FA, and piaware filters uploads to reduce data - it doesn’t transfer every message received.
It is therefore possible to have two very differently performing receivers producing similar results on the FA stats page.
You really need to measure using raw data collected locally. Graphs1090 is quite good for this. I’ve written several scripts that make use of that data to reduce it from timeseries data to a more aggregate form which can be easier to make comparisons with. Most of them are here. You really have to accumulate data over a substantial period to try an average out random variation to get a meaningful comparison though.
If you compare an airspy on 12MHz to 20MHz in the SE of the UK, I’d expect a quite noticeable difference in the number of messages decoded - a good example would be @keithma’s Martello Tower site which he switched to a pi 4, and to 20MHz a couple of weeks ago:
Apart from the glitchy spike at the beginning which is unfortunately distorting the scale, it’s still possible to see that more messages and more positions are being received from 26th Sept onwards, this despite there actually being fewer aircraft around.
Decoding more messages can help with MLAT performance since it relies on several sites seeing exactly the same message to calculate time differences. The more messages you have, the higher the likelihood that those messages will coincide. This would have more of an impact on weaker signals that might otherwise be buried under stronger ones.
I will modify the script I used previously to compare gain settings to do the same thing for sample rate. It will run for a couple of days and I’ll post results here.
Yes, I was really trying to show a high level set of data fed from the same antenna / splitter to show there is a difference, orange dongle versus airspy mini, and I have been running them for the last few months. The average smooths out what I see from day to day depending on local conditions. It is better in that sense than e.g. a day or 3 hour snapshot which is subject to local conditions. Yesterday here on south coast of UK we had unscheduled drizzile all day: a wonderful 1090MHz attenuator !!! Today, wall to wall sunshine.
I agree, but as a means of taking performance over a few days / week / month, it is “OK” as a snapshot. I will have a dive into your scripts, it has been on the must do list, but as previously posted, I have had several bouts of ’ Real Life ’ which has taken me away from the fun stuff for quite a few weeks. Mostly Honey-do list stuff in the fine weather, no getting away from the Honey-do list The summer weather was a long time arriving here. Normally where I walk the dog it is brown by mid July. This year the grass did not get brown until early September.
I look forward to your report on the sample rate script.
Well said. I have been wondering why people are pushing their gear, overclocking your PI, as caius has stated, using 20 mhz where 12 mhz will suffice etc, for what appears to be not much benefit. In the long run, would it be more beneficial $$$$ wise, if you want guts with equipment thats doing the job, in investing in a more powerful processor, which won’t have to work so hard, to get what your achieving with your poor stressed PI??
I know most of you are north of the equator and are moving towards winter, so any equipment that’s working outside will not have the issues of higher ambient temperatures adding to your “self induced” temperature stresses from over clocking, running at a higher mhz etc. Down here, I am preparing for hotter times, installing fans on my N2+'s to help keep them cool, running at 12 mhz and finding a lot of the tweaks, when trying to protect my gear, are really not worth it, if it puts strain on the equipment.
I am more concerned with my Radarcape. It can’t have any specific cooling added to it, but needs to be running in the enclosure as it needs access to a GPS antenna. Yes I could run another GPS antenna from the roof down to the office, but then I would be using the longest antenna lead I have, that will reduce the Radarcape’s performance. Any one with experience with Radarcape, I am trying to find out via community, what are the safe working temps for these units, if you can help out.
If you kill your processing unit, does not matter what RC version you chuck at the system, it is dead, which is going to cost you more $$$$ to start again.
I have admired your data sharing when you have posted your results. But I am not proficient enough to work out how you produce your visualisations apart from thinking you are running all of this on a PC. I could sort of work out how you would do this that way. But I have a number of N2+ and PI’ s, all on the same home network as my PC, but not connected to any monitors and only worked by via SSH and putty, so I am at a loss on how you transfer and view the data somewhere
I think all the plots I’ve posted on here (and other threads) have been produced on the pi directly. They aren’t particularly demanding, with the possible exception of the polar heatmap one, but that’s only if you feed it lots of data. The default settings will work fine on a pi 4. As for how to use them, most are a simple command line but occasionally have some dependencies that need installing to work. If you want to try something and get stuck you can always PM me or post on the Signal strength heatmap thread where most of my stuff ends up.
I also have a jupyter notebook running on that pi which is quite handy for messing about with data and producing plots in python. The pi 4 handles that fine as well.
As for getting the resulting plots off the pi, there are several ways. Some of the scripts will produce a web page output or put the resulting plots somewhere accessible via the browser. In that case it’s easy enough to just right click and save what you want. You could also use something like WinSCP to copy files via SSH or use an SSH client that has a file browser built in (eg MobaXterm). There’s a variety of ways to do it, but that’s probably the easiest.
Those are on the high end, but I would say that you can probably do better with that Airspy.
You’re not top when compared to your neighbors. Heck, you even left a FlightFeeder get ahead
The antenna seems all right, you are getting some over 250 miles away!
If I want to revert to previous versions of the airspy arm64 version, I copy the commit address of the relevant version: 2.1RC/airspy_adsb-linux-arm64.tgz and insert exactly where here in the current auto install script:
If the autogain puts you at 21, it’s not unlikely you could do better without the splitter getting less attenuated signal to the airspy.
I’d assume you have the LNA before the splitter at least?
Ok downloaded the link from the required version. I am thinking you still use your current shortcut, edited, to install the current RC version. Where in this line, sudo bash -c “$(wget -O - https://raw.githubusercontent.com/wiedehopf/airspy-conf/master/install.sh)” do I paste the link I have downloaded and what’s before and after that paste??
My problem is that the antenna is as high as it can go on the house, two floors and flat roof. It is surrounded by lots of houses with 2 floors and pitched roof and lots of large oak trees which limit the range so I have a very jagged max range plot. Also, to my north-west to west there is a hill behind the oak trees. Only way to improve the coverage is to resort to demolition, but I don’t think that the folks who occupy the other dwellings would be too amused The trees all have preservation orders on them, so felling is not an option either
I guess I do as good as I can at present. I have ordered a sky-hook but like most things these days it is unavailable and the store has no idea when it will be back in stock
antenna > LNA (uptronics) > 4-way passive splitter > ref system and Airspy test system. Because I feed Mode A/C I have to use the ref system as the live one as airspy_adsb does not support Mode A/C at present… here is hoping. Please?
The summer weather was a long time arriving here. Normally where I walk the dog it is brown by mid July. This year the grass did not get brown until early September.
The trees all have preservation orders on them, so felling is not an option either 
