Best Recent Content

  • Quiet switch mode power supply (SMPS) for KiwiSDR

    G8JNJG8JNJ

    In my linear supplies, I had to swap conventional silicon rectifiers for Schottky types, as the 1.6 voltage drop and 3A + forward current was producing about 5 w of heat.

    The downside of Schottky types, is that they have faster switching times, and as a result, they can produce additional RF interference, unless extra R & C snubbing components are added.

    Regards,

    Martin

    studentkra

  • Impressive!

    G8JNJG8JNJ

    To be honest, I'm not surprised.

    Many European based short wave broadcasters in the 31m / 9MHz band are massive signals during early evening / night time here in the UK, and we are not even in the target service area.

    I have to reduce their level by 20dB using an external notch filter, otherwise the KiWi complains quite badly.

    The Voice or Turkey on 9460kHz is particularly problematic, as it targets Europe.

    If you want a further challenge, try using the HFDL extension on different frequencies, to receive aircraft and ground stations, these will give you a better idea of what your Kiwi and loop are actually capable of.

    Regards,

    Martin

    smg

  • Impressive!

    smgsmg

    Im only using an cheap magnetic loop off Ali Express.

    Its 6pm NZ time.

    image.png
    image.png


    Loving the Kiwi :-)

    F5AFY

  • Whats the trick to decoding FSK?

    KenAlexanderKenAlexander

    I'm decoding an FSK signal as I write this. It appears to be from Uruguay and has information on traffic and weather around the Rio de la Plata, the major river there. Good signal considering they're in Uruguay and I'm in northgeast Thailand.

    1030 UTC

    8416.54 kHz

    It started decoding with the Kiwi's default FSK decoder settings. Will report more as I find them.

    Best advice is just to pull up the Weather and Marine frequency lists and cycle through the frequencies, staying no more than a few seconds on each one.

    73,

    Ken VE3HLS

    So Phisai, Thailand OK18sc

    smg

  • Faint "digital" signal next to one of the many China Radio International signals

    G8JNJG8JNJ

    It looks like a modulation sideband from the Radio China broadcast station, I'd guess it was similar on the others sideband too. The music played on Radio China, tends to include a lot of flute type instruments, which produce extended sidebands with regular harmonic patterns that can resemble data type signals on the waterfall.

    There are also Chinese jamming signals that attempt to make the Voice of Hope unusable, that also sound a bit like data, but I don't think that is what you have received in this instance.

    I don't think this forum allows the attachment of audio recordings, so you maybe better off asking questions like this on the UDXF IO forum.

    Regards,

    Martin

    smg

  • What are these "noise" signals?

    G8JNJG8JNJ

    Military STANAG 4285 most likely from Australia

    Regards,

    Martin

    smg

  • Whats the trick to decoding FSK?

    bensonbenson

    Well, not really abandoned as you can see in this post from April this year: https://priyom.org/blog/priyom-releases-rivet-build-91

    smg

  • Forum rules and etiquette

    jksjks

    Bump. You know, for the incoming shit-storm.

    Nate_Rsmgquadkanixnitroengine

  • Whats the trick to decoding FSK?

    bensonbenson

    You could also have a look at Rivet (https://github.com/IanWraith/Rivet/wiki/Introduction). This is an open source decoder written in java that can work with kiwi wav recordings or directly from the audio when using a virtual soundcard. The Rivet code does not do automatic classification however.

    It looked quite promising as a FSK type of signal decoder with features as automatic speed and shift adjustment, but it appears the development has stopped unfortunately.

    What you will find is that some of those signals such as CIS36-50 (BEE) can indeeed be decoded with it, but as expected seldom deciphered. Those that are in plain text (NAVTEX, DSC, MSI, FSK meteo) can already be explored with the existing Kiwi extensions.

    brgds, Ben

    smg

  • Whats the trick to decoding FSK?

    G8JNJG8JNJ

    You will have difficulty decoding anything from that signal, it is US Navy, 850Hz shift 50bd KW-46 Encrypted, Lualualei, Hawaii.

    Try using some of the KiWi's preset stations in the FSK extension, to get a better "feel" for the different shifts and baud rates.

    The most common FSK signals tend to be Russian 200Hz (or near) shift "BEE" format.

    https://www.sigidwiki.com/wiki/CIS-36-50

    https://www.sigidwiki.com/wiki/CIS-50-50

    Regards,

    Martin

    smg