Tip to Reduce Radio Interference on the RTL-SDR

A few months back we posted about a tip to reduce RFI (Radio Frequency Interference) on the RTL-SDR. Now Akos from the SDR for mariners blog has tried this tip for himself and written about his experience with it, after getting inspired to by a post in the rtl-sdr.com/forum.

To reduce RFI, the tip recommends disconnecting the shield connection of the USB cable from the ground connection of the RTL-SDR dongle. This overcomes a design flaw in the RTL-SDR which allows the shield of the USB extension cable to act as an antenna, causing unwanted RFI.

What Akos did was to remove the metal part of the USB extension cables connector to prevent any ground connection. This already reduced an interfering signal by 10dB. He also found that wrapping the connection point in foil further reduced the noise. Connecting coax to the ground then coiling it up and putting the RTL-SDR in the center of the coil also appears to significantly reduce RFI.

Update: Akos has also tried using ferrite chokes on the USB cable, and also found they significantly reduce interference.

Check out the full post by Akos for more information here

RFI noise reduction in the RTL-SDR

8 comments

  1. Peterr VK4KHP

    Sorry i, i just read the link to mariners blog, so maybe external monitor is not used, i still think, it is the computer generating the noise, wrap as many turns that will fit, of the USB cable that connects to the dongle, through a ferrite core as close to the computer side as you can, and do the same on the dongle side of the cable,

  2. Peterr VK4KHP

    how about looking at the computer, major noise, source, power cables, any other cables connected to it, cables to the monitor, oh and the monitor, try turning off the monitor and see if the noise goes away, if you are using a laptop, this may prove a bit difficult….. i know one of my monitors does generate noise on some frequencies .Ferrite cores on all of the cables from the computer, try and wrap the cables through the cores at least 2 or 3 times, more turns is better. the noise will go away.

  3. Andy

    I’m in an old house whose electrics aren’t Earth-grounded. I put in a lot of GFCIs when I moved in for that reason. I stuck a hook and the bendy-leg antenna mount on the end of an extending fiberglass pole and can get it quite a ways up and away from the house by leaning out an upstairs window and hooking it high onto the old-school tv antenna mast, I still get TONS of noise. (yes, my neighbors think I’m insane) Is there any up-to-date and practical tips for rtl-sdr v3 noise reduction in this situation in 2020, or is 2013 advice still applicable?

  4. Brandon

    I’m running into an interesting situation which doesn’t seem to happen with every software but with certain ones. Radio sharp seems at times to be emitting a ghost cover frequency on certain frequencies, namely 162.400 to be precise, and I’ve noticed that the lower the rf gain the more the ghost frequency. Now, Idk if I have to delete and reset the config, which I’ve learned from experience as a blind user is pointless unless you want the app to be completely inaccessible until you spend about a half an hour trying to use screen reader mouse commands which click on the wrong part of the window to re open the tabs you need, to fix, I’ve not found a viable solution. I’m starting to wonder if the dongle if saulty or if it comes straight down to the fact that sdrsharp tends to cause interfering signals the way it is, or what the problem specificly is. I’d have to make a recording of this and show you. But I can almost assure you there is no interference anywhere. There shouldn’t be rf interference given the nwr transmitter is about 30 minutes away from me.

  5. Emily Taylor

    I use a big ferrite core on my USB cable helps really well. I also made a Faraday Cage with ground connection to set it in, I really only use it for HF most of the time VHF and higher is usually fine :3

  6. mars

    IMO, the very first thing one should do is mount the rtl in a good metal box (I like the cast Hammond) with proper UHF/USB connectors to the outside world. Then experiment with grounding/shielding.

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