Best Awesome Content

  • 30 min disconnection!?!?

    @mdfrc99

    Wow.
    Thank you for illustrating the whole generational stereotype.
    Very funny, made my morning.

    OK here is the real answer:
    These radios are things people have bought themselves, a few hundred dollars of investment initially, then add, buying and putting up antennas, sorting out noise issues even changing what we do around the house to help the radio perform well. Then we share them for people who are interested, want to listen to radio in another location, or who themselves cannot set up such a radio, we don’t get anything back for that other than thinking that perhaps someone has benefited a little.

    If the location is good, and the radio set up well then the limited number of slots is soon used up, it’s not like a streaming radio where numbers are almost unlimited it’s just a few users at any one time and each one takes up a chunk of our internet bandwidth. The way to allow everyone to get a little for testing is to limit connection time, 30 minutes is pretty extreme but you must be looking at a very popular Kiwi (mine is set at eight hours).

    If you come to KiwiSDR with the wrong assumptions it does seem strange, if you realise these are real people trying to help each other for “good will” alone it may make sense, these are not streaming radio services. You may be able to find a less popular Kiwi that also picks up what you are looking to record they may have no time limit or a much longer one than 30 minutes.
    Bjarnerz3dvpjohnk5mo
  • Early demonstration of "channel nulling"

    Here is a very early demonstration of using the Kiwi's synchronous AM detector (SAM) to subtract one sideband from the other. So a strong on-channel signal that is covering up a weaker one (either on-channel or close by) can be attenuated. This is something I'm tentatively calling "channel nulling". There is much work to be done, but this is at least an existence proof.

    In the first image there is a local powerhouse on 882 kHz and a much weaker carrier on 880 kHz can just be seen in the RF waterfall (green arrow).


    In the second image "null LSB" has been selected from the new menu on the SAM line of the audio tab (bottom right). This puts the SAM detector in "SAL" (synchronous AM LSB) mode such that the USB component is not passed through to the audio. However, just prior to that the USB component is subtracted from the LSB, and, given the sideband symmetry of AM signals, the LSB is effectively nulled (to a varying degree). In the spectrum display above the waterfall you'll note the weak station carrier 2 kHz away now appears above the noise and, sure enough, a Spanish language station can be heard which was impossible previously.

    The "spectrum display" in this case is not the usual spectrum data from the RF waterfall but rather a single-sided spectrum of the audio channel (hence symmetry either side of center). Note that an extension called "FFT" has been selected. This is going to be an expansion of the existing "integrate" extension to include more general audio FFT and spectrum capabilities.

    The RF waterfall doesn't change between these two images because it is from the RF/IF path and not the demodulated/nulled audio.


    This technique is not perfect. Due to the subtraction involved It depends on excellent USB/LSB signal symmetry which can be easily upset by frequency selective fading. A very common problem on shortwave and medium wave at night (at a time when you're most likely to want to use such a feature). But in the presence of fading the nulling effectiveness will vary and it just might give you the chance to "bag a new one" on MW if conditions are right.

    As usual, many thanks to Youssef of AirSpy who recently pioneered this idea. A superior implementation is found in SDR# (the "Co-Channel Canceller" https://swling.com/blog/?s=co-channel). Maybe someday I'll understand how he does it (but probably not, lol).

    ChrisSmolinskinjcrz3dvpcathalferrisfractional_n
  • v1.352: new time station extension (timecode decoder)

    v1.433 February 12, 2021

      Timecode extension improvements:

        Support for JJY(Japan), RBU(Moscow), RTZ(Irkutsk), BPC(China) added.

        While running AGC delay is temporarily increased to improve noise immunity.


    rz3dvpcathalferrisKA7U
  • Windows KiwiClient & Co

    Hi Paul,

    I am assuming that you have Python installed correctly and already unzipped the kiwiclient package.Depending on how far you got with trying to run kiwirecorder and using Python on your windows machine you can try the following steps.

    1. With explorer go to the directory where you unzipped the kiwiclient repository into.

    2. Check Python is properly installed by opening CMD and typing python or perhaps python3 in your installation. To exit python type in exit()

    3. For the remote kiwi(s) you want to use, have the ip adresses and port numbers ready. 

    4. As example here Shannon Volmet parallel transmission is used on 5505 and 8957 and a kiwi receiver in Finland. Provided the remote Kiwi has 2 slots available it will record both transmissions which then show up in your above mentioned kiwiclient directory. In the CMD window type:

    python kiwirecorder.py -k 30 -s kiwisdr.oh6ai.fi,kiwisdr.oh6ai.fi -p 8073,8073 -f 5505,8957 -m usb -L 200 -H 2700

    Stop the recording after a minute with the CTRL + C keys combination.

    5. Once you got this working, have a look at kiwirecorder.py --help to see what else you want to add, like limiting the recording time, add squelch parameters, append a station name or adding a directory where you want to save those wav files.

    Best regards, Ben


    WA2ZKDdl7awlPowernumpty
  • KiwiSDR unintentionally shutting down (caused by SW update???)

    Problem Solved!

    last night, I pulled out my multi-meter and oscilloscope to make measurements on the Kiwi.

    The Kiwi is mounted in an aluminium cabinet with no external access to the 5V Kiwi barrel connector, since the cabinet also contains a LM-350 adjustable voltage regulator module, with 5.3V output soldered directly to the 5V barrel connector pins on the Kiwi PCB.

    Using the digital multi-meter, the power input to the Kiwi looked fine, 5.3V and stable.

    Then I connected the the oscilloscope to the 5V input, and noticed that the input voltage to the Kiwi contained very deep voltage drops when vibrating the cabinet and/or touching the power wiring inside the cabinet. Finally I located the problem to a imperfect connection in a PCB screw terminal connector on the voltage regulator board. Fixing the connection and re-checking with the scope to verify solved the problem.

    Lesson learned: Never trust a digital multi-meter alone when investigating problems with power supplies!

    Case closed...

    73 Knut😀

    PowernumptyKA7Ucathalferris
  • External GNSS-disciplined rubidium input?

    I know very little about the TDoA algorithm but I suspect both @jks and @Christoph are correct. Between the limited bandwidth and especially ionospheric propagation, typical Kiwi clock imperfection probably does not become an issue.

    For an appreciation of this, you are welcome to examine the phase of one of NIST's transmitters received via a visual line-of-sight 20km path and displayed on a Kiwi having a ~.1 ppb (1e-10) GPS-disciplined external clock:

    (1) N6GN External Clock WWV15

    and by a different 'stock' GPS-corrected Kiwi at the same distance and also not receiving via the ionosphere:

    (2) N0EMP Kiwi GPS WWV15

    Then have a look at a time/frequency signal via the ionosphere, CHU on 14670 kHz

    (3) N6GN CHU 14670

    or if conditions don't permit, perhaps 7850 kHz

    N6GN CHU 7850

    Whether or not the the phase wander from the standard Kiwi in (2) causes significantly extra error compared to the bandwidth and sample-length restrictions and ionospheric variations would need to be examined more closely but I rather doubt it. Thus, improving the Kiwi's local clock probably wouldn't make much difference in the TDoA accuracy or resolution.

    I think this is the primary reason that long-distance HF standard frequency transmissions tend to be only useful to .1 ppm. 1e-7, or so. Even though as-transmitted error may be 1e-12 the ionospheric path length is varying too much, particularly near the MUF for better accuracy.

    Avamandercathalferris
  • KiwiSDR production status and availability

    😀

    For the record:

    I finally received my 2 units from R&S today.

    Delivered by DHL.

    Ordered July 2020 - Delivered January 2021.

    I am looking forward to getting these up and online soon.

    😀

    PowernumptyWA2ZKD
  • KiwiSDR Monitor App

    New version out with new features - graphs and alarms.




    Rob

    http://sigmasdr.ddns.net:8073/

    ChrisSmolinskiHB9TMC
  • Wideband noise around 1.6 MHz

    At least one source identified and reduced. My station pc is powered via the 12 volt supply. Even when off it supplies 5v via usb. The internal voltage controller sent significant noise back on the 12 v bus and was picked up by the outside antenna. Probably following the coax outside, my choke was not sufficiently effective below 2 mhz.

    Found by sniffing with a ferrite rod antenna while watching the spectrogram.

    There is also some noise on my mains ground, my mains filter had a straight through earth wire.

    My SNR ratio is improving, now seeing numbers around 25 dB (P90 level minus mean level, 0 to 30 MHz)

    73 de Olaf - LA3RK

    Powernumptycathalferris
  • New KiwiSDR forum: differences and features

    Okay, after way too much effort I think attachment links are working again. There were 584 such attachments in the database and I have been spot checking the comments containing them. If you notice anything amiss please let me know.

    WA2ZKDjohnk5mo