Does someone have an idea about these birdies ?


The Kiwi is in a house where there is no computer, only a tablet.
The 3 power supplies are linear regulated ones : Kiwi, antenna, WiFi interface (Linksys)

I have birdies from 10 to 30MHz :

This seems to be computer noise. But which computer ? The Kiwi  (which is under the roof) ?

Help ? Any idea ?



  • Bonjour J-Luc
    These 'birdies' are apparently from the same source as those I have commented on, my measurements are concentrated on 23125-23127KHz.
    They sound very similar!
    The ones I measure around have two major peaks about 32dB above noise and two maybe three minor peaks about 15dB above the noise level. These birdies do seem to drift around just a little, I first found them centred on 23127.

    So far I have tried ferrite rod common mode filters on PSU line, network connections and antenna cables, then I went to Ferrite rings FT240-31 on the same cables and then got a greater reduction, but it is still 30dB above noise. Now i'm looking for more FT240-31 rings.
    The antenna used is a ukrainian active Miniwhip about 4m distant and with 13m of feeder. There are two common mode filters on this line.

    The sounds of the birdies I hear do change when I  select several more windows as separate users up the max of 4.

    What is frightening is that the birdies are still visible and audible when I remove the antenna connection leaving only the 5V power, from a linear PSU, and the netwrok cable. And they radiate into another set-up using a FCDpro+ alongside. This was fed from a 11m longwire.

    I surmise that the birdies are, maybe partially, internally coupled into the receiver. Or through a hitherto unlocated common earth impedance.
    And they can be found on a selection of the sites coupled through the SDR-hu website, although at varying degrees!
    I didn't check all of the connected receivers but I suppose someone should.

    I must add that the PSU to the network switch is a linear one, my main PC has been turned OFF for some of the tests, and the connection into the house is via optical fibre.

  • So, the KiWi could be the cource ?
  • >

    Those birdies sound pretty much like an Ethernet noise I have fought on my Kiwi with ferrite cores.
    I strung about one meter of them onto the coax near the receiver and about 80 cm at antenna end.
    That helped a lot, but didn't killed them completely. Also I found that making Ethernet cable as short
    as possible helps too.

    My active antenna is at equipment vicinity (3 or 4 meters away) that's why it catches all that noise.
    I made some experiments at my summer house with longer cable and larger distance from the equipment
    to the antenna (about 20 meters) and the stray noise picking was much less.

  • jksjks
    edited August 2017

    Be sure to follow the simultaneous thread noise at roughly 60 kHz intervals which discusses this same issue. I have moved that thread to this category to make it easier to find.

  • Thanks a lot :-)
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