Help with local interference


I am having a tough go at identifying the source of interference on my Kiwi which is noticeable from 20khz all the way to roughly 13 MHz. It seems to mimic a time signal, I am using a linear power supply to power the Kiwi. I have the DX Engineering Ethernet filters on my ethernet feed to the kiwi. My kiwi is located in my basement, away from most of our home electronics. I usually have my Kiwi connected to a Pixel Magnetic loop but recently started experimenting with a 300 foot long beverage antenna pointed NE from my Oregon location. The interference is present on both antenna but more prevelant on the beverage due to the lower noise floor I am assuming. If you would like to take a listen please search for my Kiwi under K7GFH. I have posted a couple of screen grabs below showing the interference. Appreciate any help you can provide!


  • edited December 2020

    Is it there continuously or cycle on/off over time? Holiday Lights, at your neighbors?

  • edited December 2020

    You have some massive signals in the MWBC band. They seem pretty wide there. That doesn't explain the pulse nature of what you show but I'd put a HPF on to reduce the MWBC and see what happens.

    KXTG is whacking you pretty good.

  • Presuming I have the correct K7GFH-associated Kiwi, at 1450 UTC you really aren't doing too badly. While I do hear a mains-related family of QRN from LF half way into HF, the levels aren't that terrible. Using the 10 kHz AM detector to allow hearing it (the individual lines tend to correlate and 'pop out' much more than in a narrower SSB bandwidth, they are found to almost completely disappear by 10 MHz leaving the Kiwi -154 dBm noise floor. This is assuming that the calibration is still about -16 and thus close to correct and no significant gain/attenuation on the way to the antenna.

    The largest MWBC signal is around -30 dBm but there's no other station close to cause too much worry and there's no indication of OV.

    Even at VLF you are hearing many stations pretty well, HI and Australia included. There's line related noise but I've seen far worse on many other systems. You're hearing well on 160m with several stations showing a lot of SNR.

    Because this family of QRN starts so low rather than as modulation superimposed on a family of SMPS rate beginning higher up, I tend to suspect that it is rectification noise getting either back into the mains wiring or ground currents.

    Here's a crude analysis of a little IQ/10kHz done by Audacity:

    It does have 'ragged' edges around full-wave rectification (120 Hz) which may be what's responsible. I can't account for these.

    OTOH, maybe the problem you are asking about has chosen this time to be absent.

  • is on the same Pixel antenna in a suburban residential neighborhood. I have a bunch of MWBC very nearby, so notch out the 3 offenders.

  • edited December 2020

    Good morning,

    Thank you for the replies.

    WA2ZKD - Yes, the signals do cycle off. They are gone this morning. I will check throughout the day to see if the come back on. If they come on tonight then I think you hit home run on the Christmas lights although my closest neighbor is 300 feet away to the North. I cycled my lights and they are not the culprit.

    The MWBC bands are much stronger with the beverage versus my Pixel Loop. I am a little surprised as the MWBC stations are NW of my QTH and the beverage is pointed NE. I have read a few posts where you discussed the notching of those MWBC stations. I will work on that in the next few days.

    N6GN - Thank you! I do have overhead power lines nearby and in particular, a noisy one that I have let the power company know about. Once they clean up the lines around here I believe what you talked about will improve - fingers crossed! Very impressive overview of my receiver, I need to read it a few more times to digest it all. Thank you again.



  • Jay,


    If you look at my 8073 box, you'd never guess that there are 3 notches on the local big guns. Has little effect on the other BC

  • Will do, thank you!

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