I have been feeding ADS-B with MLAT enabled via a raspberry pi 2 for several months now.
While looking at my ADS-B stats page, I have noticed that my receiver is not being used for MLAT >90% of the time. If I look at the hourly messages chart, I see that the receiver will send messages for a couple of minutes-hours, then drop out for many hours at a time.
When I click on the “view anomalies” link I get this message: “This feeder is not being used for multilateration because it’s timing information appears to be unreliable…” It goes on to say that my location is wrong, or the pi is low on CPU.
My location is set dead on, and there is plenty of free CPU on my pi. My SDR dongle is the flightaware pro (plus?) with the integrated 1090mHz filter, so I doubt that it is the issue.
I only have a very general understanding of how MLAT works, so I’m not sure where to start troubleshooting. Is the timing information referenced in the “anomalies” message from the pi system time, an internal clock oscillator on the SDR, or something else? Should I be trying to fix the pi system time, or looking at a hardware issue? Could this be caused by signal reflection from surrounding buildings? There are plenty around to cause interference.