Medium Wave: Offset Atlas – all 10 kHz channels, 24 hours

The “Atlas” shows screenshots of all 10kHz channels on Medium Wave within a 50Hz window, sometimes better. You can download it for free to determine accurate and stable offset readings over 24 hours (zoom in by e.g. 400%)

With the new Elad FDM-S3 and its OCXO/GNSS-stabilized clock, I did a 24h recording of the whole medium wave band on January 19, 2021 in Northern Germany. Free software SDRC V3 enabled me to make up a spectrogram of each channel within a window of 50Hz width, and at a frequency raster of 10kHz. You can easily see:

  • sign-on/sign-off
  • fade-in/fade-out
  • accurate and stable frequency offset over full 24h down to a millihertz
  • frequency control of the transmitter’s oscillator (stable, drift, sinus, sawtooth …)
  • propagational effects (doppler, scatter …)

The format is PDF, DIN-A4, landscape, resolution 300dpi – see screenshot at the bottom. This allows you to zoom to a factor of about 400% to search for details and better read out of the time/frequency scale. It weighs 559MB. You can download it here, and open it with your PDF reader (you can also point your mouse cursor onto the link, click right mouse key, and choose “Save under …”). Leafing from one page to another gives an interesting overview.

Yes, a similar Atlas showing a raster of 9kHz is under way and will be published also here in due time. It is also planned to publish a general article about the background, about what to do with such a tool, and how to do this by yourself.

I am sure that it will open some new horizons on Medium Wave DXing, including accurate offsets over up to 24h.

Aloha: KUAU from Haiku/Hawaii, received on January 19, 2021 by DK8OK. Proofs are frequency, plus the rather unique fade-in/fade-out in the European afternoon.

Comments and suggestions are appreciated:


  • Thanks once again for your contributions – not just entertaining but also truly inspirational.

    A dreamer like me gets all kinds of wild ideas, too many to bore everyone here. Well, just a couple :D.

    1. Consecutive, or longer-spaced, captures. Saved in a graphics format with “layers”. Viewed with adjustable transparency, to help recognise differences.

    2. SDRC “Tags” feature extended to show enclosed time/frequency region boundaries graphically on waterfall; each saved with unique key in a database to support additional logging information.


  • I’m afraid this is not really something new. We could do this already since 2013 with the Perseus/Jaguar combo. OK, this was not GPS stabilized but but relatively correct using well known stable carriers.

    • Thanks, Guido – and I know Jaguar quite well. As far as I know, however, there has never been published a full-blown overview like the “Atlas”. Jaguar excels in each and every aspect (just to mention the integrated stations’/offset list). It should be transformed to also other SDRs as Perseus (somewhat fading?) to attract an even broader community. BTW: May we await a Jaguar-based “Atlas” from you? 73 NIls, DK8OK

      • Could be done Nils, but it’s different every day and also depending on the chosen antenna. The Jaguar community keeps a close look on the new emerging SDRs. But the developer needs also a bit of cooperation from the developer. Elad stopped replying after a few mails.

      • … thanks, Guido – and I now eagerly await your Atlas. It would be much better, as you can show how different antenna directions behave, and what difference different conditions do make. My modest approach was just aimed towards accurate and precise offsets (i.e. based on OCXO and GNSS) plus sign-on/sign-off times. Nothing more. With a system gain of about 70dB over a 10kHz channel, plus the gain of the sensitive optical pattern recognition by eye & brain, different days and directions (for the latter I don’t have antennas rolled out) seemed not being that important – at least for such a first try. Now it is up to you!
        Jaguar & other hardware than Perseus: that would be highly appreciated. And it is a pity that the communications between the Jaguars and the ELADs obviously has broken. I like to recommend the SDRC V3 approach which controls nearly each and every SDR on the market. Simon has been very responsive to adapt his software even to engineering examples (like FDM-S3) and SDRs which he never touched (like my Winradio Sigma). He also developed lightning-fast a bridge to RX666 and RX888, just from analyzing the recordings.
        This seems to be a perfect and universal approach. Jaguar is a very tempting and perfect software for the medium wave aficionados. THis software really deserves to support a large range of SDRs.
        73 Nils, DK8OK

      • Sorry Nils, I didn’t want to be offensive. Just wanted to say it was possible before.

        Simon is probably the most experienced software developer in the SDR world and he is a professional. Ilpo from Jaguar is a hobbyist that tries to serve the MW DXing community doing the best efforts that he is capable of.

      • Guido – it is all ok. Simon is a professional, donating his very professional software for free to each and everyone. He is open-minded for any suggestion, maybe convincing (better) or not so convincing (ask just me …). He is also constantly upgrading and updating his software – also for free. I respect this work very much. I also respect the work of Ilpo, who is perfectly serving the community with a software showing unique and unsurpassed features. Maybe it is a good idea that both work together. If I remember correctly, the Jaguar people had been a bit reluctant in sharing full access to their ideas and software. However, this may have changed. But I don’t have a Perseus anymore to try this. If any opportunity opens, I would be pleased to be among the beta testers … after that it will be literally “fool-proofed” …
        73 Nils, DK8OK

    • Not much good keeping it under your hat… publish, publish, publish :D.

      • Here is a bit outdated link to the free Lite version

      • Sorry (@Guido) that remark was directed @dxantwerptest who suggests we should all know about Jaguar capability without being shown examples.
        In this case, I meant: “I have never seen a Jaguar graphic anything like the Nils-published channel profiles”, that is to say 24-hour recordings at narrow (50 Hz) bandwidth. Nils is continually pushing the boundaries of what we should be trying to achieve with SDR technology, and I for one am deeply grateful for this constant source of inspiration.
        To be clear, I *do* realise that Jaguar can generate a *live* display of something similar. But these hi-res waterfall extracts have been possible for some years using Simon Brown’s free “SDR Console” tool “Data File Analyser”, illustrated on his website at This is actually a highly configurable tool with many further options well worth exploring.
        There are other Jaguar qualities/features that would be welcomed by myself and many non-Perseus users. It would be lovely if the Jaguar developers, in the true spirit of Amateur Radio, shared their expertise and revolutionary ideas more widely in the community. For the moment, that IP is limited to the Perseus world which (for all its historical significance and excellence) is beginning to contract with the arrival of better technology.
        Also, FWIW, SDR Console (MS Windows only) *does* support the Perseus, albeit with some reservations about low sample rates.
        Paul White

        P.S. @Nils, I’d be grateful for info about the original recording sample rate and Analyser configuration options?

      • Paul,

        When you do a search for “Jaguar SDR” in Youtube you will find a lot of examples about the capabilities. Jaguar might be “low-profile” but that is probably while it is a Medium Wave Only tool.

        Yes I know Console’s Analyser. I use it a lot for FM-DXing during the Es season.

      • I don’t want to abuse Nils’ blog with unnecessary comment, but hope he will bear with me one more time on this topic.

        @dxantwerptest: Not new, but not well-known outside your Perseus/Jaguar circle.

        @Guido: Thanks for your suggestion. Amongst all the many YouTube search results from “Jaguar SDR”, there are 177 videos actually featuring Jaguar in operation. I found that there are in fact others, but apparently not tagged as such (and ignored for now).

        The earliest and most numerous (124) are by John Faulkner (Skegness DX), beginning April 2016.

        Here is a summary:

        124 John Faulkner 2016 (58), 2017 (6), 2018 (1), 2019 (2), 2020 (54), 2021 (3)
        3 Guido Schotmans 2016 (1), 2017 (1), 2020 (1)
        1 Gerard AM DX 2017 (1)
        12 Paul C 2018 (1), 2020 (11)
        1 Mika Mäkeläinen 2018 (1)
        2 DishDX 2018 (1), 2020 (1)
        2 digitalmediafan 2019 (2)
        2 ve6wz 2020 (2)
        1 Wolfgang Wundsch 2020 (1)
        1 satnipper 2020 (1)
        28 DX Central 2020 (14), 2021 (14)


        Most concentrate on single channel-width displays (typically 8 kHz wide) and short duration (usually under 3 minutes). A few have a rather longer timeline, 10-20 minutes, and perhaps a little narrower bandwidth. In general, they focus on documenting idents – I suppose that is the point of those videos!

        Another thing I noticed is concentration on the dominant station on a channel, even when others may be heard fairly clearly in the background. Is it maybe that digging deeper doesn’t make good “cinema”?

        Admirable DX but Jaguar’s strengths are really not show-cased in this selection – either generally, or in the specific area we have been discussing in this blog post.

        *EXCEPT*: a brand new pair of videos from Steve (VE6WZ), a total half-hour (whistle-stop) presentation of Jaguar Pro recording and playback posted last October.

        How I wish they had been available a few years ago. I’m a little clearer now how cleverly Jaguar integrates the YAS (low-res spectrum) with high-res recordings – something that other SDR software authors might look into.


      • Paul – thanks, and I appreciated the discussion, as I appreciate the work of you and others. I wasn’t aware about the many Jaguar videos. The reason, why they flew under my radar is twofold: there seems no public full-blown version (neither free, nor for e.g. a donation), and it sticks solely to Perseus, to which I am not that glued to anymore (despite the tons of laurels showered on this smart SDR by a smart genius – also from me). I will now leaf through many of the videos and hope the discussion will have at least two results: a greater visibility of this interesting topic of chasing just carriers, and to spark writing even more and universally usable software for this. The latter just has started with e.g. Carrier Sleuth of Chris Smolinski for blackcatsystem, and Ivan Mongorov is tweaking Pskov – his software of NDB fame – also facing the medium wave community. 73 Nils, DK8OK

      • @ Paul. To put things strait, I and dxantwerptest are the same. I realized that I used that old log in and changed the name afterwards.
        Jaguar software was free for a longer time until Nico from Microtelcom was asked to write an sbs file for covering the medium wave band with a width of 1.6 MHz instead of 2 MHz. That’s why now 50 Euros is asked for the Pro version. My short lived Studio1 license costed a lot more.

        I was going though my Youtube Videos, and you are correct, they were badly tagged. And also mine are mostly DX catch videos, not instruction videos.

        The big difference between Jaguar and other SDR software is that you can switch between a full band 9 kHz or 10 kHz display hiding the stations from your home continent as shown by Steve (VE6WZ).



  • Wonderful things you are doing Nils.
    73, Harris K9RJ

  • As always you are making a wonderful job! I expect your news!

  • Hi, Guido, I guessed that was you :).
    Yes, that 9/10 kHz thing looks *very* useful.
    In fact, the list of “clever stuff” seems endless.
    I’m seriously thinking of one day buying a Perseus, “when my ship comes in”, just for the pleasure of running Jaguar Pro (which I happen to think is good value for €50).
    Happy hunting!

  • Hi Nils, good morning. Out of curiosity, if one plans to run a suvey like yours (aprox 2MHz, during 24 hours), how big should be the storage media to accommodate the IQ files? Do you recall what was the disk usage rate (I guess around 1GB per minute?). Have a great weekend! pu3hag

    • Good question, Garcia – with 1.536MHz width (FDM-S3/16Bit), you need 530.8GB/day. I did many recordings over 24h of 24 or even 30MHz width/16Bit. There you need around 8 to 11 terabyte. No problem, if you have two separate (!) USB3.0 connections to your PC. One takes the input from the SDR, the other shuffles the output to an external HDD like MyDuo Book. So far, I didn’t feel any need to use an (much more expensive) HDD for this. This setup, however scratching at the limits, works fine. 73 Nils, DK8OK

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