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. K4VBB

    K4VBB XML Subscriber QRZ Page

    Negative. As a matter of fact it's getting worse. The attached picture shows the repetitive nature of the signal across the 40m band. In the lower pane you can see that the SDR software interprets the noise as a signal -- the highlighted portion on 7.276. In the upper pane you can see the frequency variation of that same signal. Since propagation on the band is minimal tonight there's not much other traffic.

    Attached Files:

  2. K4VBB

    K4VBB XML Subscriber QRZ Page

    You're not far off.

    I've taken steps to mitigate any power issues in the shack, and (thankfully) the noise doesn't reach my QTH with any measurable amplitude through the power grid. However, I do believe that it is radiating through the power lines that run between a set of 3 street lights in the 'hood like a giant underground antenna.

    It is also possible that the noise is coming from one of the houses that are close to these street lights, but a little probing leads me to believe that this is likely not the case. The area with the loudest noise signature is directly in front of a house where an 80+ year old man lives -- not likely that he's growing weed in there. What I can do is follow the path of the noise between these street lamps.

    I've documented the affected frequencies in the recent past. I hear it as low as 4.687 and as high as 8.176. In the past week or so I've seen it creep up higher in frequency, however, so I think I need to take another survey. It's also starting to reach sufficient amplitude that it may be affecting aeronautical mobile traffic, but since I don't fly planes I don't think I'll ever know that for sure.

    I've yet to draft a letter to the city/utility as I still want to get a second set of eyes on the source. I want to make sure I have all my bases covered, and want to be as sure as I can about the source before I engage them. Anyone ever deal with power company noise issues with a favorable result?
  3. K4VBB

    K4VBB XML Subscriber QRZ Page

    Here's another screenshot, but lower in frequency range. This covers between 6.48 and 6.75. As you can see it's particularly bad in this range --thankfully not a HAM band-- with the noise reaching S7 when tuned into it. There does not appear to be a "primary" frequency for the noise, however.

    Attached Files:

  4. WQ4G

    WQ4G Ham Member QRZ Page

    I have a similar RFI issue here at my station also. There is a distinct BUZZ in my radios that starts just before dark and stays active until just after sunrise. I have determined that it IS being conducted into my house and shack through the power lines. There are four 'services' being fed from the same transformer and the signal is present on ALL the wiring at those locations. I get the strongest signal from one of the locations and I have made contact with the owner of that location. Unfortunately, he denies that he has anything that would 'buzz' my radio and he, so far, has not allowed me in to look for the source. So most likely I will not be able to stop the RFI and will have to HOPE that it burns it self out sooner or later. Maybe it will burn down the location at the same time.

    And, now for a rant....

    IMO RFI problems should not really exist. We should not have to be plagued by RFI and we should have some recourse when we are. EXCEPT this is exactly what a certain segment of the population wanted (and received) when they demanded TAX CUTS. Because of these tax cuts the FCC has had to scale back enforcement til it is almost non-existent. Tax cuts do not educate children. Tax cuts do not pave roads and build bridges. Tax cuts do not provide for Police, Fire, and Military. And, tax cuts do not provide the FCC with a budget sufficient to provide enforcement. IMO this is a case of 'be careful what you ask for - you might just get it.'

    Dan WQ4G
  5. K8XG

    K8XG Ham Member QRZ Page

    I have experienced this now for more than a year. Lots of it during April-July, and then November-December but never 24/7. It would sometimes come up around 1-3pm and go away. Then it would come up just before dark and last ~2 hours. Most times always the same duration.

    They were spaced at 20hz and was detected on my 33 foot vertical on most all bands. It was not detected on my 80 meter low NVIS Dipole. I traced it with my FT-818 to the street behind me, and various points on the cable and power line wires.

    It has not happened since after new years yet at least at te4h times I have been operating.

    Something different I have detected most every other day is a broadband noise floor on my spectrum analyzer that adds Very Strong Bacon frying to all 2 meter simplex signals under S9+20 over. Its across all the 2 meter band, but the repeaters mostly are louder than it. It will also cause my APRS digipeater to not decode S9 signals. Plotting times on and off, it might be a plasma TV and it always seems to come on just before the TOP of any hour, may last a few hours and turn off just after the top of an hour. I plot it by looking at my APRS logs that have not received any packets, and we get such packets about every 15 secs at my QTH.
  6. KJ4VTH

    KJ4VTH Ham Member QRZ Page

    Experience this almost every morning and it is most gratifying! :D
    K8XG likes this.
  7. N2ZD

    N2ZD Ham Member QRZ Page

    I have the EXACT same noise on the low bands. It’s not in my house, I can even hear it in the car when I drive around short distances. Sometimes it drops out. I’m in NYC so go figure! It’s definitely a common issue or common device.
    For example, I hear that very same noise on 3844 MHz and up and down 80m, I also hear it on other bands.. you’re not alone

    Regards Richy N2ZD
  8. AA5MT

    AA5MT Ham Member QRZ Page

    Find a ham in your area with a spectrum analyzer that can go mobile if necessary.

    Does it happen with no antenna?

    Have you tried another computer? Computer power supplies are notorious.

  9. W0AEW

    W0AEW Ham Member QRZ Page

    It took the local power company months to finally locate the horrible noise source I had. It was a faulty power pole lightning arrester. It was almost a mile away yet came thru the power lines very strong. It affected another ham two blocks away.
  10. K8XG

    K8XG Ham Member QRZ Page

    My Siglent spectrum analyzer portable shows the same thing I see on my radios on foot. Cables lines are conducting the noise from some place else.

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