Best Recent Content

  • Enjoying new filters and SAS

    Mr John!!! You are a star!!! 😂

    I came back to the Kiwi forum after six-plus months away, and what do I find? You have resurrected a 70-year-old forgotten/ignored technique I've been trying (unsuccessfully) to promote for over a year. And longed to experience since reading about it in my teens, 60 years ago!

    Your "SAS", or something apparently equivalent. Coherent lower/upper sidebands demodulated and presented to left/right ears.

    This was often referred to as "binaural" in the literature, but that's a term hijacked for two other different audio techniques in the last 20 years or so. Now I think of it as "sideband binaural".

    For me, the brilliance of SAS is primarily in spreading all the (non-coherent) noise across the sound stage, leaving the wanted channel centred and allowing the brain to focus via the "cocktail party effect". Adjacent channel interference tends to come from the sides as well.

    A more subtle benefit is often found for co-channel stations with small carrier offsets from nominal. The tiniest spatial separation is enough to improve aural discrimination so much more effectively than with plain AM or even SAM. Sometimes even much weaker stations can be resolved.

    In my opinion this is an indispensable tool for serious DXing. I hope many other listeners are going to explore and enjoy its capabilities - and the word gets around to other potential customers.

    If you've researched the topic you will know that KiwiSDR is unique. Binaural sideband AFAIK has never been implemented in analogue radios. And NO OTHER SDR program offers this feature. The couple that provide a "BIN" or pseudo-stereo function do something completely different, completely missing the potential achieved by Kiwi. There MAY have been just one SDR going down the same track, but that looks like a dead donkey now.

    I'm very curious to find out how you implemented this (I did it with Hilbert) and have a couple of ideas arising from my experiments. Don't know if you feel like chatting?

    Thanks to Ken for his post that directed me here, and to you for having the inspiration and making the effort to provide it.

    All the best

    Paul

    njc
  • Kiwi with 2m converter/switch added

    Today's v1.427 release adds a "frequency scale offset" field for each antenna on the admin page, extensions tab, "Antenna switch" entry. After updating to v1.427 you must also install the latest version of the antenna switch extension from github.com/jks-prv/KiwiSDR-antenna-switch-extension

    When any antenna is selected the new offset values will be used and completely override (and overwrite) the offset value from the admin page config tab. A value of zero means no offset, so the usual frequency scale of 0 - 30 (or 32) MHz.

    Any active user connections will get a popup panel requesting a page reload when the offset changes. No offset change is made when "antenna mixing" is enabled because it isn't clear what to do in that case.

    Powernumpty
  • Early demonstration of "channel nulling"

    To null, use SAS mode and select the "audio" tab on the main control panel. On the bottom SAM line you should find the "channel null" menu. Select "null LSB" or "null USB". Make sure the PLL carrier is around 0 Hz (+/- 100 Hz maybe). If it's way off then make sure you're tuned to the station center frequency, switch to AM mode briefly, then back to SAM. The PLL should lock.

    Did you mean SAM mode? It's the only mode in which I find the "channel null" menu.

    WA2ZKD
  • DRM Heard

    Rádio Nacional da Amazônia testing.
    
    73 Chris
    


    KA7U
  • Early demonstration of "channel nulling"

    From the CHANGE_LOG file. The user interface is definitely rough, but at least you can give channel nulling a try in this update.

    To null, use SAM mode and select the "audio" tab on the main control panel. On the bottom SAM line you should find the "channel null" menu. Select "null LSB" or "null USB". Make sure the PLL carrier is around 0 Hz (+/- 100 Hz maybe). If it's way off then make sure you're tuned to the station center frequency, switch to AM mode briefly, then back to SAM. The PLL should lock.

    Use the spectrum function of the new "FFT" extension to visualize the nulling result. It's best to put the spectrum/waterfall aperture mode on manual so the spectrum doesn't rescale on you when the signal is nulling. You can enable the peak detect ("Pk" button) on the WF tab to see the difference. Because the nulling is happening in the audio path the regular waterfall and spectrum signal levels are not effected. Same for the S-meter. And currently same for the FFT and integrate modes of the FFT extension, although this might change.

    v1.425 November 26, 2020

      Channel nulling, preliminary release

            See forum post: http://forum.kiwisdr.com/discussion/2169/early-demonstration-of-channel-nulling#p1

       

      Audio FFT extension:

        Rename and expansion of former "integrate" extension.

        Adds continuous audio FFT and audio spectrum modes to existing integration mode.

        The audio spectrum function is particularly useful in visualizing the effectiveness

          of the new channel nulling feature of SAM mode.


      Admin security tab: added option to enable/disable console tab access from the local

        network. This in response to a few Kiwis that still have trouble determining

        their local network address, e.g. when using unsupported WiFi dongles.


      Prevent open menus from unexpectedly closing when colormap averaging event occurs.

      Update embedded URLs pointing to the forum.


    KA7Ubenson
  • Kiwi with 2m converter/switch added

    Hi Guys,

    I don't post here much but have something now... Spent some time designing & building a bespoke switching board for my Kiwi as shown in attached photo>

    The unit is accessed here: sdr.hdarc.co.uk:8073/

    Then go into the antenna switch extension and select number 3. The local club uses this for FM nets on 145.375MHz, which comes out on 29.375MHz. The board also has a changeover relay (orange in photo) for my HF transceiver plus many other features.

    It would be nice if the antenna switch extension could automatically set the frequency offset, but we can't have everything!


    73, Rob.


    jksKA7U
  • KiwiSDR: New App for Android Devices

    KiwiSDR map and receiver on Android devices?

    John Seamons has recently approved a brand new KiwiSDR Android app for publication (by frantsch).

    The app provides access to the Wideband Shortwave Radio Reciever Map (http://map.kiwisdr.com). As you might know, the map shows worldwide locations of KiwiSDR receivers covering the entire shortwave spectrum (1-30 MHz). Hitting one of the marker symbols will provide you with a link to open the chosen KiwiSDR receivers´s home screen. Get back to the initial KiwiSDR map any time by pressing the back button of your Android device.

    All you need is an Android type mobile device, and a high-performance network connection (4G, WiFi).

    Interested? Go get it:

    Google Play Store Link

    And: Please spread the news!

    73 & 55 frantsch (35HB432)

    cathalferris
  • 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
  • New KiwiSDR forum: differences and features

    Welcome to the new KiwiSDR forum, hosted on kiwisdr.com and running the latest Vanilla 3.3 forum software.

    All of the forum content from valentfx.com was copied over including attachments, avatars, inboxes etc.

    The most problematic issue will be external links from other places pointing to specific forum posts. Forum links were previously of the form valentfx.com/vanilla/discussion/... and need to be changed to the form forum.kiwisdr.com/discussion/... This is of course impossible for immutable (non-editable) content like links embedded in Twitter tweets. It was not possible to automatically redirect references from the Valent forum for various reasons. So if you have editable links into the old forum please update them. However, links to old posts on Valent will continue to work as long as Valent hosts the old KiwiSDR content.

    Also, the time to edit your posts is not limited on this forum (previously the limit was one day). So if your post contains a link back to Valent you can simply edit it to correct the link per the above. In theory this shouldn't be necessary as the database was scrubbed very carefully to update all the links.

    The forum has a slightly different look but basically the same features. The biggest change is editing posts. There is no longer a "preview" button. When using the new paragraph icon on the left margin, and also when double-clicking on words and making text selections, the formatting changes are immediate. It is a "what you see is what you get" (WYSIWYG) interface. Experiment and you'll see how it works.

    The search box is at top right. Use the "Mark All Viewed" button on the top bar as all the previous viewed information has been reset.

    If you are having any problems (e.g. can't login, can't post, getting error messages, etc.) please email support@kiwisdr.com

    Christoph
  • v1.419,423: added non-NBFM squelch

    My 2 cents regarding UI. Could the speaker symbol to the right of the recorder button go red during Squelch recording and white/green as today on the other modes. In the "Audio" menu the "Scuelch" text could also go red with the recorder on ?. When i have the word. I have 4 KiwiSDR in use and what a wonderful experience this has been. My first KiwiSDR was indeed a very capable and interesting product, very early i became impressed and satisfied with the hardware and now many, many firmware updates later it still amazes me how dedicated John and his team always is. Many thank`s John for one of the most interesting and rewarding experiences in my 45 years as a Radio Amateur. And almost 40 years as a professional radio engineer. 73`s to you all.
    WA2ZKD