Patrizio seeks information about mystery signals he’s discovering across the HF bands

Many thanks to SWLing Post contributor, Patrizio Cardelli, who has discovered some interesting signals on the HF bands and is seeking information about them.

A little background: Patrizio asked me about these signals a few weeks ago and based on a quick glance at the spectrum and waterfall images I assumed it was DRM (Digital Radio Mondiale). I was wrong, of course. Had I looked at the actual frequency and bandwidth, I would have immediately realized is was not DRM. My email load has been so heavy as of late, and my time to reply at such a premium, I rushed through the reply–my apologies, Patrizio!

Patrizio followed up with this message:

Hello Thomas,

I hope this message finds you well. I wanted to share my recent radio exploration based on your advice. I followed your suggestion and investigated a sample signal within the 60-meter band, specifically settling on the one at 4.962 kHz.

I attempted to decode it using the Dream software but encountered no success. It seems this isn’t a Digital Radio Mondiale (DRM) transmission. To rule out local QRM (interference), I tested various Kiwi SDR receivers across Europe, both to the south and north of my QTH. Interestingly, I managed to pick up this signal everywhere, with a stronger intensity noted in the northern locations.

I’m eager to publish this article to find out if other Shortwave Listeners (SWL) have been able to decode this transmission. Additionally, I’d like to mention that similar signals, either continuous or intermittent, are present on various HF frequencies.

I look forward to any insights or experiences others in the community might have regarding this intriguing signal.

Audio sample:

While I recognize these signals now, and I’m sure most of you who cruise the bands have seen/heard these as well, Patrizio is a relatively new SWL, turns out, and I thought it might be fun exploring just what these signals are. 

Readers: If you know what these signals are, please comment. Indeed, I’m sure there are a number of SWLing Post readers who have hands-on time with generating these signals as well in a past life or current career. Let’s explore!

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30 thoughts on “Patrizio seeks information about mystery signals he’s discovering across the HF bands

  1. Angel

    Hi all.
    The signal is STANAG 4285. Unfortunatelly, it was received in AM mode so nothing to decode.

    Best regards.

  2. Ken

    It sounds like one of the NATO STANAG modes. There are some software products (Sigmira, Sorcerer) that can decode it, but there is a high likelihood it is also encrypted, so decoding will get one nowhere.

  3. DE KC9NRB Bryan

    Reminds me of the signals Russia used for something called “over the horizon radar” back in the 80s. But I think it was just a way they were using to jam specific frequencies as was suggested earlier in the replies

    1. Pedro M.J.Wyns

      I guess this is some kind of COFDM signal that might be used for flash trading. As far as I know they are the only people setting up HF stations on multiple places using expensive R&S log periodics. Try to locate the site using TOA on KiWisdr systems.
      Pedro ON7WP

  4. Don jennings

    Don, AI3N. Hope this is not a double:) Exactly 3 Khz bandwidth says it is not just noise and the fact it is on a frequency used by VOA could be suspicious but if it is digital chances are nobody will have the right decode software so good luck decoding it as the strength says some government agency is responsible so they would use very proprietary coding.

  5. Don jennings

    Don here. AI3N is my call and the thing I noticed is the bandwidth is almost exactly 3 kilohertz so very controlled and I would go with deliberate jamming and the fact VOA uses that frequency is suspicious. Maybe it could still be some crypto encoding but hearing it all over Europe says it is a powerful signal and not just a test setup. If it is digital nobody will be able to decode it unless you have access to a quantum computer, hi hi.

  6. Frank AA5IT

    I’ve tried for the last couple of years to decode data on the frequencies that have this DRM- looking pattern. It’s definitely encrypted.
    It would be nice to have a piece of software that could analyze, determine the encryption key and present the data being transmitted. I’m sure the CIA has software developers that constantly work on stuff like this. It would be interesting to know one of the people working on it to see what progress has been made…

  7. Patrizio

    Wow, 20 replies to this post! It seems like the topic is quite interesting, and Thomas’s blog has quite a following. I want to express my gratitude to everyone for the thought-provoking insights and technical guidance. In reality, my intention is not to decode a signal or this particular signal specifically. I attempted to do so only to understand if it was a DRM transmission. The frequency is within the 60-meter broadcasting or tropical band, and this signal prevents me from listening to some stations at night. Most likely, due to the unfortunate war here in Europe, I will come across more signals of this kind.

  8. Fred

    I remember back in the ’70s. Some signals were lost at the horizon when most of the signal went out into space and very little reflected back down.
    Very reminiscent of those types of signals.
    Probably wrong, I have been wrong before.
    Just passing thought and I didn’t duck when it went by.

  9. Aurelia Peters, W0KEH

    Practically speaking, *anyone*, licensed or not, can listen and attempt to decode *any* signal, provided they have access to the necessary equipment. Even if it’s against the law (which would be dumb) how is anyone going to know you’ve received/decoded a given signal?

  10. Lou Barbaglia

    I thought it might be used by the banking/finance community, they have been operating on experimental licenses for a few years now.

  11. S?ndel

    That is a channel marker. You will find them all across the HF spectrum. It comprises of a noise generator fed into a sideband transmitter. There are many noise setups available.
    These are a staple in russian military and *services comms and they have no regard of any band plans. They keep a channel busy for eventual later use and sometimes are used to jam other transmissions.
    You can find them inside all ham bands, broadcast bands and everywhere besides, jamming even the maritime comms and WX transmissions.

  12. Anonymous

    STANAG 4285 from DHJ58 Ny Glücksburg. Actual frequency: 4960.200. You need to tune it at the bottom of the frequency band pass (not centre) with a 3.2 kHz filter.

  13. Erwin

    4.962 kHz ? Do you mean MHz maybe ?
    Does the 60 meter radio amateur band-plan not start at 5.3515 MHz ?
    Are licensed amateurs allowed to investigate and try to decode signals outside the radio amateur bands ?
    Check your license. The situation is different from country to country, even in Europe. Sometimes you are allowed to listen to these signals, but not try to decode. Sometimes you are not even allowed to listen. On a shared band it might be different as well. Are we primary user of the 60 meter band ?
    Know what you publish …

    1. Harald DL1AX

      It´s in the 60 m _broadcast_ band. Check the international band plans. The digital signal on 4962 kHz is interfering with Voice of America Sao Tomé and Voice of Hope Zambia. Of course we can try to find out who is interfering with broadcast stations in a broadcast band.

    2. Mario

      You do not need an amateur radio license to decode signals outside (or inside) the amateur bands, at least in the USA. Not sure what you mean by “investigate” though. We’re generally just having fun. Hope this helps.


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