FlightAware Discussions

HOWTO: Airspy mini and Airspy R2: Piaware / dump1090-fa configuration

This is the first time this problem has come to my attention.
If you read the quickstart guide on the airspy page, it’s clearly stated:
https://airspy.com/quickstart/

Anyhow a note that a firmware update may be required if your Airspy is older than 2016 might be a good idea.

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Speaking of Airspy… I have tried different sampling frequencies and I don’t understand the benefit of using higher SR.
I can use 12, 20 or 24… great. But for higher SR I need to lower the “e” to “fit” into my one core CPU 100% usage.
To me it almost looks like the benefits of running at 24 or even 20 with lower “e” are not so visible. Does anyone see the same, or is just depending on the local conditions and the actual CPU capability?

I’ve mainly focused on finding the right combination between -e, -w and gain. Running 20MHz SR and a somewhat overclocked RPi4 with passive cooling.
From my experimentations I’ve found that some gainlevels give a higher CPU load than others. My system max out if the gain is 18 with -e 10.4 and -w 5. CPU is lower if the gain is higher or lower. I suspect (but can’t prove) that this is some kind of “sweetspot” for my system and location producing the best signal quality for the system to work with, but I can be utterly wrong :crazy_face:

Got inspired by your post so I’ll try to lower the SR to 12 for some time to see if that makes any noticeable impact on the performance/stats combined with changes to -w and -e.

My post had a mistake, I meant as variable the -e. The -w is the default 3.
In my case, at night, when are less planes, the CPU usage goes high. Since I don’t think I am missing anything interesting, I let it hit 100% on one core in that case (just a few flights).
So, to keep variables at minimum, I am interested in the trade-off between the Sample Rate and -e.

Are you just referring to SDR radios, or will a system backup to USB also cause problems?

Anything that uses a fair amount of data can cause problems.
The USB 2.0 bus is limited to ~480Mb/s. The airspy uses a lot of this.
You can use devices that don’t use much bandwidth, maybe a GNSS/GPS dongle or something powered by USB that doesn’t use much or any data (a uputronics amp for example).

A system backup to USB would use a lot of available bandwidth. If the backup device is USB 3.0 and plugged into a 3.0 port on an RPI4 then you may be OK.

I’ve never found a combination of settings where SR=20 that come close to receiving the same number of planes / positions I can get with SR=12. Just guessing, I’d say I easily lose 20% of decoded messages when operating with SR=20. This is on a dedicated Pi4, no lost samples.

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I am on a i7 CPU, so the -e values are higher than on a Pi4. Supposedly after a certain value, there are only diminishing returns. So that’s why I have asked…