Blinking aircraft!
I recently added a new PiAware setup that had worked great for a week and then one day some of the planes on the web UI keep blinking on and off. Restarting piaware and dump1090-fa didn’t help any, and I knew the device was healthy otherwise. Thanks to Claude, it figured out that I had week-old stale 978 MHz UAT reciever data laying around on disk, and every second when the SkyAware Javascript file downloaded the two 1090 ADSB and 978 UAT position files it was freaking out about the stale 978 positions and hid them. The next second ticks, fetches the old file, displays them, hides them, repeat.
It turns out this was was because I originally had both 1090 MHz and 978 MHz SDR dongles hooked up to my Raspberry Pi to collect both ADSB and UAT data, but I had to unhook the 978 SDR dongle due to power constraints. I masked and stopped the dump978-fa service because it kept crashing and trying to restart over and over again. Stopping the service left behind the old data in /run/skyaware978. Removing those data files stopped the blinking. Rebooting would have worked as well because /run is volatile, but who likes unnecessary reboots without root causes?
This is all because my RPi4 doesn’t have enough juice to power two SDR dongles, an external USB-SSD drive, and a GPS hat. Technically it works until it doesn’t, usually when I’m doing a lot of activity on the Pi it exceeds its power capacity and reboots on me. I had bought a cheap powered USB3 hub at Walmart to put the SDR dongles on, but when it was plugged into the Pi it refused to boot. The Internets tell me this is likely due to the hub back-feeding 5 volt into the Pi over USB and confusing its power circuitry. Unfortunately it didn’t back-feed enough to power the Pi by itself. I even tried to daisy chain a old unpowered USB hub between the Pi and the powered hub, it let the Pi on but it couldn’t see the SDR dongles on the USB bus. So sadly I’m waiting for another powered USB hub to come in that I can take back out there. Pity, because I was really curious to see how much UAT traffic I could pick up and now I’ll have to wait.
Also, who needs a J-pole mount when you can just zip-tie both antennas to a concrete block and put on the roof?
