Unplugging the FA dongle


#1

I just bought a 2nd FA Pro dongle (blue one), to use with a different antenna or as a spare.

I’ve been trying to compare the two dongles. To do so i unplug one from the cable going to the RPi, and attach the other one.

This appears to cause dump1090-fa to fail (or something). ‘Top’ shows that dump1090-fa goes from using 27% of CPU, down to 0.3% after switching dongles. So then i do ‘sudo shutdown -r now’ and after a couple minutes the CPU usage is back to normal and i’m getting signals.

Am i doing harm to the hardware or software by abruptly unplugging the dongle?

I want to make sure the newly-bought one performs as well as the 1st one i got two weeks ago. Any comments welcome.

On another note, today i managed to set up dynamic dns (with no-ip.com) and port forwarding, so i can access my Piaware away from home. wn1z.ddns.net

Orrin.


#2

I fried one of my FA Pro dongles. But for the life of me, I don’t know how I did it.

Most likely done while swapping out with the power still applied to the pi.

I’m pretty sure that after swapping dongles, I’ve always had to reboot the pi in order to get piAware to recognize it.


#3

Unplugging the dongle and plugging it back in will probably not damage the prostick. You definitely want to keep the prostick away from high voltage and static discharge though.

When you disconnect the prostick the dump1090 software decoder doesn’t know why the radio was disconnected. It goes into a refresh mode every few minute to try and check if a dongle was reconnected and then initialize the radio again. So you should only need to wait about 3 minutes after plugging in the dongle to start up again from the refresh timer.
You can see the refreshes in the piaware.log file:

cat /var/log/piaware.log

There is a command to restart the software decoder instead of waiting for the refresh

sudo systemctl restart dump1090-fa


#4

Patience never was my big suit.


#5

Thanks… using ‘shutdown -r’ etc seems to work faster than the restart command… the two FA dongles (same model) seem to perform about the same.

High voltage & static discharge: yes. Also, in my situation, disconnecting the antenna whenever i transmit more than a watt on HF/VHF/UHF. The dongle radios are notorious for getting fried by close-by RF. I know about the various solutions to the problem – i built an RF-limiter for my sdrPlay RSP1 in case i forget to disconnect the antenna. (Like DX Engineering’s ‘Receiver Guard’). Which will help but is not a guarantee. Disconnecting is best.


#6

ever thought to have both plugged-in and use an antenna splitter ?


#7

Antenna splitter will also split the amount of power in half. One receiver will have half the signal power and the other receiver gets the other half.

In a digital TV system this is works very well since the signal is very strong and can recover the original data from the lower powered signal.

Splitting ADS-B signals you will also lower the signal strength by half to each receiver. This will cause far away low powered signals to be lower than the threshold needed to decode the signal. I have seen 20-40% decrease in max range after using a splitter.