Wit's end with unknown source of RFI

Discussion in 'General Technical Questions and Answers' started by K4VBB, Dec 17, 2019.

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  1. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    Another option is to acquire a portable shortwave receiver, such as a Sangean or Tecsun brand, to locate the noise source. You will probably use it more than you might in the future. They are designed to work well with their short whip antenna and be hand held. Get one with a digital frequency readout so you can set to the known noise frequency.
  2. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    Good, I assume you also checked things like VOIP phones, cable modems, etc. that often have internal battery backup.
  3. W0AEW

    W0AEW Ham Member QRZ Page

    It sounds like the OP's RFI is on 24/7. Is that true of OTHRs? I thought they were on intermittently.
  4. KA2IRQ

    KA2IRQ Ham Member QRZ Page

    They are on intermittently and they are also a pulsed system. The sound of this RFI is not OTHR... but it is a requirement on QRZ.com that there be at least one "OTHR" response per RFI complaint, along with several comments to turn off everything in the house (stuff we all know already).
    KB0MNM and WQ4G like this.
  5. K1VW

    K1VW Premium Subscriber QRZ Page

    I have a very similar issue, it shows up equally on my FTDX3000, my IC7100, and my SDRduo. Somewhat on 40m, bad on 80m, NOT bad on 160m, which I think rules out AM broadcast. It's consistantly spaced in a similar fashion, although I don't remember if it's a 20khz spacing. In my case it wasn't an issue last winter but then it started in April, and I can't think of anything which changed at that time. I've shut off things around the house, I don't think it's in my house. The next time there is a power outage which kills power to the entire neighborhood I've got to remember to check it then.
  6. KF5LJW

    KF5LJW Ham Member QRZ Page

    Just let me know what day and time you want it.
    KD0CAC likes this.
  7. KB7WG

    KB7WG Ham Member QRZ Page

    I was not aware of OTHR being a standard comment on QRZ for RFI. And I was not aware that OTHR had a particular spectrum pattern or sound.

    I have read of many different spectrum patterns and sounds for OTHR. There seem to be many modes. And have read of new stations coming on line.

    And it might be many more functions or measurements with this digital tech......than just radar.

    Then again, it might be a power line sub-channel monitoring/control technique.

    Do you get it when connected to a dummy load?
  8. K4VBB

    K4VBB XML Subscriber QRZ Page


    currently on the OMISS 40m SSB Net. Other HAMS are currently complaining about it as well. This pretty much rules out a local source.
    N2ZD likes this.
  9. K4VBB

    K4VBB XML Subscriber QRZ Page

    The fact that others on the OMISS net were reporting this noise seemed to defy logic to me, even though I have absolutely no reason to believe that the other HAM radio operators were mistaken about what they were hearing. So when the net was finished, I went "DF'ing" with my resonant loop and my FT-891, and I believe I've found the source of the interference, but it wasn't easy. I had to do a lot of walking, mostly in wrong directions. Turns out it's on the street right behind my house.

    Most of the street lights in our 'hood' are of the LED type. However, I did find one that appears to be a HID. I think that the reason that this light was so hard for me to spot is that its power supply may be inducing the RF into its own electrical system, using it's own power wiring as an antenna. Since these extend out some distance from the actual lamp, using standard direction finding techniques was difficult. The excellent DSP in the FT-891 and a narrow passband helped a lot. Since the noise 'looks' like a signal, the DSP recognizes it as such and treats it accordingly. This allowed me to progressively turn up the DSP and get closer and closer to the source.

    I also believe that the reason I was getting reports of others having the issue is they likely have a similar issue in their neighborhood. Since band conditions were not all that great tonight, I believe that their issue -like mine- was that the noise made it more difficult to pull out the weak signals.

    I'm going to check with the local clubs and see if they have something a little more scientific to help me nail this down. Even if I do, it looks like I might have to live with it until this light dies.
  10. W1VT

    W1VT Ham Member QRZ Page

    Yes, there is so much noise verbal reports are pretty much meaningless. Spectral plots showing exact times would be more conclusive.
    There is no long distance 40M propagation mechanism that is 24x7 today. Long range interference should match propagation times.

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