I’m not sure what these AirSpy graphs are indicating. For example: is the RSSI number good or bad? Traditionally, the closer RSSI is to zero the better. What do DF counts represent? Overall what can I tweak?
The setup is: FA antenna (in attic) - 25’ LMR240 - RPi 5 - AirSpy Mini
Hi ua549,
The DF counts are counts of the different typed of DF (Downlink Format) mode-s messages. There are many different types used for different things. The most common, DF17, is the ads-b extended squitter which is when an aircraft constantly sends out its position. Many of the DF messages are responses to either ATC ground radar, and even TCAS aircraft interrogations.
The link below has some great, very detailed info on the specifics of each message type. The page linked below shows the basics, if you scroll down to the “4.4 Mode S format” section.
https://mode-s.org/decode/content/introduction.html
Some programs like VRS also display real-time counters of each message type along with a basic description of the purpose. VRS documentation also has some good info on this.
Regards,
-Dan
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What about the other graphs? Performance is good, bad, ugly? Suggestions?
Do you have a pre-amp? The airspy is pretty deaf at these frequencies without one.
There is an FA Blue filter and an RTL-SDR LNA. I didn’t include it in the path above.
The full setup is:
FA antenna (in attic) - 25’ LMR240 - FA Blue 1090 filter - Nooelect Lana - AirSpy Mini - 3’ USB - RPi 5 - PoE Ethernet
They don’t look too bad.
I would suggest you try running with a sample rate of 20 MSPS and a preamble filter of 60 ( -m 20 -e 60 ). This should result in more weak signal decodes and the Pi5 will easily handle the load.
The shape of the charts also seems to depend on the antenna’s “field of view” - here are my two setups (both -m 20 and -e 60):
Main system with locally unobstructed 360 degree view of the horizon (Pi4B, Airspy mini, Uputronics LNA/Filter, 5 metres LMR400, Vinnant antenna with -g auto)
Test system mounted lower down a slope, about 30 metres away, obstructed by trees and terrain. (Pi 5b, Airspy R2, Nooelec Wideband, no filter, 5m LMR200, FA 66cm antenna, with -g 16)
I’m using the AirSpy Mini with a Pi4. I have been using the “standard” 1090 performance graphics load. What is the source for these AirSpy graphs?
Wiedehoph’s Graphs1090.
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@Jerryh47 Hi Jerry, I have the same setup as you. I followed the instructions here and the Airspy graphs just popped up! Maybe do a re-install of Graphs1090?
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