Airspy R2 and dump978-fa

FlightAware ADS-B Flight Tracking
1

I took advantage of of Black Friday sales and now have two Airspy R2’s. I have one configured and running with dump1090-fa per the discussion here: HOWTO: Airspy mini and Airspy R2: Piaware / dump1090-fa configuration with only minor troubleshooting/debugging to identify the specific device via serial number.

I’ve run into a roadblock with dump978-fa. I’ve installed drivers required and configured the dump978-fa config file per discussion here: HOWTO: Airspy mini and Airspy R2: Piaware / dump1090-fa configuration - #465 by wiedehopf . However, I never see any data in Skyview or piaware-status, and I can’t track down where the issue is. The Orange dongle with filter will see traffic (with the appropriate dump978-fa config settings).

Has anyone here successfully gotten this configuration to work? Any help here would be greatly appreciated.

2

I tried a few times but never got it to work. I would really like to get it to work as I have several airspys and already have a 978Mhz DPD antenna with Uputronics amp(on the mast) feeding a v1 rtl-sdr that has been moded to provide bias-t. I have Spare RPI4s(the current uat setup is running on an old RPI3B+) and odroids (XU4 and N2) that I could use.

3

I wonder if this is the airspy not liking the sampling rate. dump978-fa wants a very specific sample rate (2.083333MHz). The airspy may not support this, and dump978-fa doesn’t have any support for resampling from other rates.

4

FWIW I dug into this a bit and, from my reading of the code…

a) the firmware only supports specific hardcoded sample rates. 2.083333MHz is not one of them;
b) if you try to set a sample rate that is not supported, the firmware responds with a USB stall and libairspy returns that as an error;
c) the airspy soapysdr driver silently ignores the error, so dump978-fa has no way of knowing that the sample rate setting failed

tl;dr: dump978-fa is not going to work with an airspy any time soon; it requires either firmware or libairspy support for arbitrary sample rates, or a resampler implementation on the dump978 side.

5

Interesting, thank you for the reply.

With FlightAware working on native Airspy support for dump1090-fa and integration of UAT into a shared map, is there any anticipated work on rebuilding dump978-fa to mirror dump1090-fa including the additional SDR support?

6

Much like the airspy work on dump1090, I’m happy to point people in the right direction and merge contributions, but it’s unlikely I can find much time to build the support myself.

For dump978, the SDR support (via soapysdr) is already there. The limiting factor is the need to work around the airspy hardware limitiations. If someone wanted to contribute a rational resampler implementation that would work (e.g. the airspy can do 6MSPS; 6MSPS * 72/25 = 2.083333)

The underlying bitrate of UAT is 1.041666MHz and there are no integer multiples of that which the airspy supports, so it’s unlikely that you can avoid needing a resampler even if you redesigned the demodulator.

7

You must have misunderstood something, Flightaware is not working on that but rather @gtj0.
If you don’t see the Flightaware Staff after the name then the people here are not FA employees.

8

The useful bits from my DSP: https://pastebin.com/RWWEdn2k

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