FlightAware Discussions

Locally generated electronic interference (RFI)

Outside of receiving and feeding ADSB data I also experiment in Software Defined Radio in the shortwave spectrum. I use both an SDR Play RSP1A and a Version 3 RTL-SDR dongle with Spyverter upconverter. I am always dealing with RFI that is locally generated. I have two kids and plenty of electronics they have as well. I noticed the V3 RTL-SDR dongle has its problems with RFI even though it has its own metal case. I had made sure that I keep the hardware tighten plus I used some small metal tape strips I cut and used them to make contact with the case and the outer shell of the USB shell which works great to get the dongle to ground. Then, I look over at my Three Flight aware Pro sticks and see their plastic unshielded cases. and within a few inches three unshielded Raspberry Pi. I started this topic to see what are people’s opinions of RFI shielding.

With all of the computers around the house and the Pis up in the roof and the switch mode power supplies and phone chargers and the light dimmers and the LED lights and the plasma tv I have given up trying to cure the QRM.

The minimum noise level from 160 through to 15 M is 20db over S9.

It drops about 10db if I cut all power to the house and run the receiver on battery.

Sadly, no more HF for me except when i go camping and then i have to make sure no-one around is using LED lighting.



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Beeing fairly new to this, how far away does these kind of units affect the Pi?
I only have LED lights in the house, a plasma TV downstairs, a lot of switched psus all over the house, etc.
I have installed (a pretty cheap) filter on the power outlet that supplies the Pi with power, but I still have ripples all over the signals when I use SDR#. Is the propagation strongest over the power line or the air?

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I’ve put some effort into quieting down the receiver system. Keep in mind the issues include both conducted and radiated noise and interference.

At the LNA— I used a low noise linear power supply to power the LNA. That supply is not shared with any other part of the system. I also shielded the front end filter and the LNA in a metal box.

At the SDR — The AirSpy Mini is supplied with a metallic housing. Make sure the SMA connector is well grounded to the case. I split open the USB cable and cut the red wire to power the SDR with its own +5 volt supply and isolate it from the Raspberry Pi power which certainly has plenty of “digital” noise riding along with the dc.

At the Raspberry Pi — I use an Ethernet connection and turn off the board’s WiFi (“rfkill” command) to quiet the local RF space a bit.

It can be hard to quantify the results of individual measures but taken together the system performance is improved.


It didn’t take Google long to make the connection and then suggest this link in my chrome browser.

Now all i need i need is a secure quiet site with power and net access to set up the remote station. :smiley:

Not likely.


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Last night I googled for a USB power supply something like what would be on the professional scale

Something simple like a LM317, LM7805 or LM340-5 three-terminal linear regulator is going to be lower noise than most USB switching supplies. Search the auction sites for “linear 5v buck” to find modules.