Local QRM, 60 KHz intervals

edited May 2017 in KiwiSDR Discussion
I just noticed something I believe is new to my local RF environment.  It seems to start around 15MHz or so and is prominent all the way to the end at 30 MHz.  The "signals" are at roughly 60 KHz intervals.

I also notice a bit above 12 MHz another anomaly that produces a "kerchunking" sound pattern with a repeat cycle for the pattern something less than one second.  I have attached images for both things, which I guess could be related, but I have no idea what might cause these.

I disconnected the antenna to verify everything disappears.  I have a new UPS in the shack (not powering the Kiwi though) and this is the only thing I can think of that might be "new" in my environment.

Does any of this ring any bells with anyone?





  • Chuck,
    repeating lines happen here from time to time. Sometimes grounding the antenna and then ungrounding causes the signals to go away, sometimes not. Random stuff from an RF neighbor somewhere. I often have harmonics from MW band at random times. I think the wideband signal is over the horizon radar and currently it looks as though maybe two or three stacked OTH signals around 12.64MHz. 
    Ron - KA7U
  • Thanks Ron,

    I had very recently moved the Kiwi to the other side of the shack, but have the same antenna cabling and power source etc.  I'll play around a bit tomorrow and see if messing with the antenna etc.

  • jksjks
    edited May 2017
    Chuck, in your first photo the strong signals under the red vertical lines and yellow Kiwi passband look very much like the unstable carriers from a switching power supply. I have seen that pattern many times before. Zoomed out like this it sort of looks like a narrowband AM signal where the instability is causing modulation sidebands.

    In the second photo there is the same strong, unstable carrier on the left. But the Kiwi passband is over what looks to me like two overlapping 100 kHz wide CODAR signals: costal radar https://en.wikipedia.org/wiki/Coastal_ocean_dynamics_applications_radar

    I've been meaning to add a section to the website with screenshots and audio samples of typical interference signals. I see the same problems over and over again (switchers, ADSL, electric fences, noise floor rise due to BCB overload, etc.)

  • That is what I wondered about (a switcher) but had no idea what to expect, so it sounds like that is the culprit.  When I move the same antenna to the K3 and tune to the same frequency, I do not hear anything.  I will experiment with that some more.  I do not have any new switchers in the house (that I can think of) so perhaps it is a neighbor with something new.  At least it is not in the lower part of the HF spectrum that I am interested in and I think most my "visitors" use.

    I see the same signals when I switch from the low 80M CF wire fed by window line to my 6BTV vertical (looking in the 21 MHz range) I see the same junk but much weaker.  

    The CODAR was more of a curiosity, I did not think it was related to the 60 KHz lines.

  • I added my simple Faraday cage to keep some of that stuff out. You can see the pix in my review post.
  • Do you mean put the Kiwi in the cage?  Does this have an effect when the junk appears to be coming in from the antenna?

    I really need to shut down my my main UPS which is new to at least see if that is the source.  The Kiwi is powered on a different UPS that has been here longer than the Kiwi.  But I need to be in the proper mood to go to that trouble.

  • I started out with the cage to eliminate stuff within my shack etc. When "new stuff" appears I can rule out that entrance point without touching a connector. I have found that my own LCD TV gets in through my Loop but I an going to experiment later in the week. I have also found that stuff can get on the RX feedline and radiate into the RX antenna, a choke at the antenna can curb that.
  • Seeed has been sending me prototypes of a nice aluminum case with small internal fan. Don't know the schedule or price, but hopefully reasonable. I'm trying to get them to resell those nice audiophile linear power supplies too.

  • JKS:  I connected to your beta  and see much the same 60 KHz spaced lines in the upper HF range similar to mine.  Today I tried to shut down as much as I could in the shack with no effect (Ethernet hubs, UPS units, USB hubs, External drives etc.), so I am giving up for now.  It is not a problem at 14 MHz and below which is where both myself and most users hang out.

    I disconnected the items from AC so none of the wall warts or UPS units had AC input just to make sure.  

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