Noise at roughly 60 KHz intervals

I'm seeing a BUNCH of noise signals from about 11MHz to 22 Mhz (?) at roughly 60 Khz intervals.

Is this a known electronic design issue? Is it possibly a signal from one of the computers in the vicinity?  If so, is there a fix?  

Thanks!

Bill 

Comments

  • jksjks
    edited July 24
    Probably not a Kiwi design issue, unless you've supplied your own, older Beagle that is known to have noise problems (see http://kiwisdr.com/quickstart/index.html#id-e14) What you describe is typical for one type of SMPS we've seen. 60 kHz is a common switching frequency.

    Switch off the other devices until you find the culprit. Try filtering the mains input to your Kiwi linear power supply and perhaps Ethernet and antenna feed line.

    There are plenty of Kiwis that are in very quiet noise environments with few system noise effects, e.g.

    wjniemi
  • Thanks, will check it out.

    These seem to have appeared suddenly, well, I don't think I had them a couple of weeks ago and here they are.

    Got to move it out to the shop!

    Best,

    Bill

  • More
    30/60KHz spurious signals.

    I
    have a KiwiSDR with BBG that was purchased as a set. It is supplied from a 5V
    3.5A linear psu.
    After sorting out the interfacing to the network, it worked.

    I have a choice of two antennae, a 12m longwire, or a PA0DRT copy active
    mini-whip. There were a few unwanted signals to clear up with ferrite rings but
    as I go down towards the noise floor there are spurious signals that DON'T go
    away with application of ferrites or screening.

    Also
    I can see similar unwanted signals on a selection of already wired and active KiwiSDR
    web receivers.

     

    I
    chose one of the stronger spurii showing on my RX, at 23127KHz +/-3-500Hz,
    as a
    working point,
    and I
    tried and tried to reduce its level in the receiver, the spurs are about 30dB
    above the noise floor.

    Very similar spurii can be seen on several other KiwiSDR RXs accessed via the SDR.hu
    list and I can post the screen dumps when I’ve worked how to do that.

     

    For
    the moment I have given up as I can't get rid of these signals.

    They are even still there, at reduced levels, when I have removed the antenna
    and all my peripheral circuitry, leaving just the power cable (with large
    ferrite ring), and the CAT6 cable (with FT240-31 rings at either end) with the
    antenna input shorted out.

    In fact I surmise that the unwanted signals come directly from the IP network
    communication. 


    Has
    anyone else seen this? 

    And better still has anyone found a way around the situation/problem??

     

    The
    network switch is a Netgear Prosafe GB switch, model GS105 that is supplied
    from a linear psu; and the connecting CAT5e cable is about 5m long. 
    I am trying to find someone to lend me an
    alternative switch.

      Peter

  • I'm curious to see if the different switch fixes this.
  • what happens if you connect a PC directly to the Kiwi and shut off other network stuff? (as a test)
  • Makes me wish I hadn't thrown out all those 10base-T to 10base-FL converters 15 years ago.

  • I put the KiwiSDR back into it's cabinet yesterday and was surprised to see the noise floor (at 23127) had dropped from about -120-130dB down to -150dB. Silly numbers! has anybody else noticed a similar change? And the spurious levels seem to have dropped as well
    The latest version installed is 1v14.
  • I found an awesome paper that talks specifically about wired Ethernet RFI issues (starting on page 12): http://audiosystemsgroup.com/RFI-Ham.pdf
    Although it seems your use of type 31 toroids at both ends of the cat-5 is the best first step.

  • I faced the similar RFI problem with my ethernet cables inside the garage where the receiver risdes.
    The only solution (partial) I found is to keep the Ethernet cables as short as possible. That can be seen
    on the welcome photo of my SDR.
  • I have the Kiwi on my "IT Shelf" in the basement and I don't think I see this even though it is nestled up need my router etc. I have #31 ferrite on all the cables and also have it under a Faraday shield.

  • Regarding the use of a direct link KiwiSDR to PC or Laptop. It didn't work at all.

    Also no one I know has a spare switch for me to borrow, will I have to buy one??

    And I see that someone else has also commented on a very similar situation.
    See -Does someone have an idea about these birdies ?  by F1JEK/P

    here is an illustration showing that it is just my installation that has this phenomenon.


    imageimage
    spurious signals.png
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    I1CRA - kiwisdr.briata-23127_72dpi.png
    1025 x 546 - 471K
  • Sorry, I meant --- ISN'T JUST my installation
  • edited August 29
    Hi Bill, Peter and others,

    I'm fairly sure it's originating from your ethernet cables and / or router.

    As an experiment today I connected a 1inch diameter single turn RF 'sniffer' loop to the end of a short length of coax and had a 'sniff' around my KiWi's

    Sure enough there is a very strong signal as described at 23127KHz and also at regular intervals of approx 60KHz over most of the spectrum.

    The next three screen shots were taken with the 'sniffer' loop in among all the ethernet cables going into my small 4 port Netgear network switch that sits under the desk.

    image

    image

    image


    The fourth image shows the very weak interference when the KiWi is connected to my antennas.

    image

    In my case I've added a lot of ferrite rings around the various cables going to and from my KiWi's (see next photo)

    image

    To suppress RF radiation on cables at frequencies around 23MHz the optimum results would probably be obtained with something like 8 turns of the ethernet cable through a ferrite ring made from either type 43 or 31 material.

    Note that you need to add ferrite rings on all the ethernet cables and at each end of every cable.

    I hope this helps.

    Regards,

    Martin - G8JNJ













     
    Ethernet DC -30MHz.png
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    Ethernet 22 - 24MHz.png
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    Ethernet 23MHz.png
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  • jksjks
    edited August 29
    I run my Ethernet switch from a linear supply. But of course inside the switch has an on-board 3.3V SMPS to regulate the nominal 5V DC input. I've been meaning to "sniff" that to see what frequency it runs at and check if it correlates to the spurs that I see.
  • edited September 26
    62 kHz increments of dirty but stable carriers are very common. 
    It is generated by the digital circuits inside wired LAN switches and LAN routers.
    Ferrites on all the I/O CAT-5 cables and power supply cable of the LAN can help to suppress it. 
    Getting the antenna further away from the computer and LAN helps a lot. 
    Coaxial ferrite choke isolators at the feedpoint of the antenna, and where it gets close to the LAN helps also. 
    Image of 62 kHz LAN noise:
    image
  • It looks as if there are two threads, no.778 and no.827, dealing with these very similar conditions.
    Thanks for the info and advice Martin, I'm slowly working through cabling permutations and lots of ferrite rings.
    I've gotten another KiwiSDR with ser. no. 2050 for second installation and this is attached to a "Beagle Bone Green" with a label BBG217021961 stuck to it.  So I can do a direct comparison after the tests with different ferrite toroids attached in various places are completed. So far no real progress has been made and I haven't found or borrowed a different switch either, new ones cost money, plus I'm a little fed up with getting nowhere fast.
    Is there any data not yet published relating to the older BBGs obtained separately to a KiwiSDR so that we can check against the ser. no.s of the BBGs supplied in the sets. 

    WA2ZKD wanted to know if i'd tried a direct connection between the KiwiSDR and a PC.
    Well, I didn't get networks comms to start at all so I wonder if this is only possible with a USB connection?
    Or maybe if I had a 'crossed over' network cable, this connection might work. Does someone have any thoughts on this?

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