FlightAware Discussions

MLAT problem after upgrade to 3.8.0

After having upgraded to 3.8.0 (sd card version), I often get the the MLAT error “the feeder is not being used for multilateration because its timing information appears to be unreliable”. That was not the case with 3.7.2.

As per MLAT Feed Anomaly, proper system time does not matter with regard to MLAT.

MLAT went green after reboot only for a while.

Any ideas? Known issue of 3.8.0?

No known issue, most likely your power supply has gone bad.

Hmmm, MLAT desync appeared just after upgrade to 3.8.0 …

Did you check regularly before? I tend to leave things alone, but have a closer look after I change or upgrade something, and then might spot a problem that was there before, unnoticed?

Hi Guys:

I have the same problem … I have restarted every day and it is not working properly.

Any suggestions or ideas to correct the problem?

Regards from Querétaro, MX (MMQT/QRO)
Pablo A. Dávalos B.

At first I thought that it could be related to the drop of in the US, however, @nimzok
is in Russia. He had a dramatic drop off in MLAT traffic this week. It does look to be upgrade related.

What do the logs say? Are there any obvious error messages?

Since the upgrade to 3.8.0 was done, the MLAT indicator is red every time I look there. After reboot it shortly reverts to green and then falls back to red. Will try with another charger as suggested by @wiedehopf.

That’s an issue in itself.
You really should be using one of the dedicated RPi power supplies or the results are anyone’s guess.

Phone chargers are just not suitable.

It’s probably more accurate to say that phone chargers are an unknown quantity, often with their performance only tenuously linked to their stated specs. Some will work, some will be unreliable or not work at all.

I’m using a spare LG phone charger to power a pi 4 at the moment and it’s working fine, but then I’ve tested it with a dummy load up to it’s maximum output of 3A and it holds its voltage perfectly. Others I’ve tested can’t deliver anything close to their stated output with the voltage collapsing when you start to load them up.

If you don’t have the facility to test properly, it is definitely safer to just go with the official power supply. It’s cheap enough and you get something that is known to work.

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For the time being, I used an original Apple charger with 2,1A output (a little bit below the 3A required for RPI 3B+…) as I don’t have another dedicated RPI charger at home. And surprisingly, no more MLAT problems since one hour … Will keep monitoring the issue and buy an RPI-dedicated charger ASAP. @wiedehopf - thanks for the hint it might be the power supply.

After a couple of days, I can confirm MLAT is running smoothly. It appears replacement of power supply did the job.

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Just to illustrate my point above, here is a graph of a test I did on a few phone chargers and the current official Pi 4 PSU:

These measurements were taken with a small dummy load with voltage read at the plug, so what the Pi would see and therefore includes any cable losses.

The official Pi PSU output is specified at 5.1V 3.0A. It maintains above 5V until the load reaches 2.25A, and the voltage recorded at its rated output was 4.91V.

The Xiaomi charger has a specified output of 5.0V 2.0A. It drops below 5V almost as soon as any load is put on it. At 1A it’s still supplying 4.97V however and at its rated output it’s supplying 4.87V. It has a protection circuit that cuts the power above 2.2A. This might be OK to power a Pi 3 and dongle, but add an LNA or Pi 4 and it would be marginal.

The Asus charger is also rated at 5.0V 2.0A. I tested this with the same USB-C cable as used on the Xiaomi charger, but also with a micro USB cable. The power loss through the micro USB connector is considerable - at the 2A rated load, the micro USB was showing only 4.65V, whereas as the USB-C cable was showing 4.83V. This charger would be problematic powering a pi 3 (and this is the case, since I tested it on a pi as well) unless with an extremely good quality connector and cable.

I’ve only tested one phone charger that is up to powering a Pi 4 (an LG 3.0A USB-C one) which I don’t have detailed data for, but is currently running my ADS-B pi.

Considering the low cost, getting the official power supply would seem to be very worthwhile, immediately eliminating a common cause of stability problems.


Fully agree with @caius

July 2017


March 2018