Help identify an RF noise

Discussion in 'General Technical Questions and Answers' started by K0JM, Jul 10, 2018.

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  1. K0JM

    K0JM XML Subscriber QRZ Page

    My suburban neighborhood has lots of RF noise, but this one is really giving me fits. Does anyone recognize what sort of device might be creating this??? I usually see it late morning to late afternoon on weekdays local time -- only occasionally on weekends. It is intermittent, on for about 15 seconds then off for a few seconds and it begins again. It pretty much wipes out the entire HF spectrum.
  2. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    I don't see the image. But a sound recording (audio) can reveal more than a spectrum plot.
    WB5YUZ likes this.
  3. K0JM

    K0JM XML Subscriber QRZ Page

  4. K7JEM

    K7JEM Ham Member QRZ Page

    Something with around a 12 or 13KHz switching frequency, maybe a power supply or monitor, etc.
  5. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    I agree, "looks" like that.

    If you tune in dead-center to one of those frequencies, does the signal remain perfectly stable and stay right on that frequency, or does it drift slightly?

    Something rock-stable usually really is crystal-controlled, or frequency synthesized using crystal as the basis; if it drifts a bit, it's not and usually is some sort of switchmode power supply.
    WB5YUZ likes this.
  6. K8JD

    K8JD Ham Member QRZ Page

    Spread spectrum DIGI mode nearby ???
  7. AA7QQ

    AA7QQ Ham Member QRZ Page

    Door bell transformers can cycle like that when they are at the end of life. They heat up, then the thermal switch cuts power, then it resets.

  8. WB7TDG

    WB7TDG Ham Member QRZ Page

    New high efficiency clothes washing machine? Ours does that.
    WB5YUZ likes this.
  9. WB5YUZ

    WB5YUZ Ham Member QRZ Page

    It is almost impossible for anyone to tell you what the noise is. You will have to find it, yourself.

    Have you started by opening the main breaker and seeing if the noise goes away? That is almost certainly a better use of time than trying to find someone who happens to have seen the exact same thing on a display and can tell you exactly what the source is; I've seen quite a few of these threads, now, and I've never once seen someone identify the noise source from a screen shot!!! Anyone who could do that reliably would probably never have to buy a round again.
    KB4QAA likes this.
  10. N5AVF

    N5AVF Premium Subscriber QRZ Page


    Please have a listen to the Youtube link I posted below. It is a sample of the twice daily RFI generated by the system my rural electric co-op uses to read meters. It's a "BPL" system that destroys everything below 10 MHz. Fortunately it's only active at 10AM and 3PM daily for about an hour. Not prime time operating hours for low band HF anyway.

    Does it sound anything like this?


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