FlightAware Discussions

Disable —fix on SD Card image

Is there a way to disable —fix on the SD card image of 3.8.1? I am having the large number of Tracks with One Message issue. I have tried different cables, a different RTL-SDR ADS-B LNA, and a different dongle. If I drop the gain I have to drop it so far I start losing range and positions. The last thing I’d like to try is turning —fix off. Unless someone has another idea.

Not with a sdcard image; you’d need to use a Raspbian base image + package install, then you can edit /etc/default/dump1090-fa however you want.

That said, the single-message-track rate from --fix is usually not a big deal. Do you see any bad data making it to skyaware? What are the actual rates that you see? The single-message-track rate is essentially measuring messages that passed the CRC check but which dump1090 did not end up using, so those tracks don’t make it into the output data. So the rate itself is not a problem, it’s just an indicator that there are probably-bad messages making it through the CRC checks. If the rate of single-message tracks is unusually high, that might mean that the rate of undetected errors is getting unacceptably high.

A low (absolute) rate of single-message-tracks is fairly normal, independent of how many real aircraft you’re seeing. If you’re not seeing many other aircraft, then the single-message-track rate might seem high in relative terms, but still be a normal rate.

That could be it. My aircraft numbers are pretty low these days. The single message tracks as counted by Graphs1090 probably average about 70 tracks/hour. It’ll vary up to around 100 and down to almost 0. I’ll attach the graph. Otherwise my range and everything are pretty good. Over 200NM. My messages over -3dB can be high mainly because the local police have a plane that flies low over the city a lot. But I choose to not drop my gain too low so I don’t lose a bunch of range.

That rate does seem pretty normal, so unless you’re seeing bad data I’d retain --fix

--fix is good at squeezing out a bit more range so if that’s what you’re after then it’s worth keeping if you can.

1 Like

This is normal on very low traffic. See my chart for the last eight hours which include the night times:
Once the traffic comes back, the number of valid tracks is increasing

Sounds good. I’m not seeing bad data show up on SkyView. I’m assuming bad data would look like planes showing up in a single location and then disappearing. I’m definitely not seeing that.

Mostly you’d get bogus aircraft without position in the aircraft list.
Aircraft from the red tracks never made it into the list because only 1 message was received.