Soldersmoke: Mattia Zamana’s Amazing Direct Conversion Receiver

Many thanks to SWLing Post contributor and Soldersmoke host, Bill Meara, who shares the following from the Soldersmoke blog:

Mattia Zamana’s Amazing Direct Conversion Receiver

Thanks to Ed KC8SBV for sending me this awesome video. It looks like Mattia built this receiver way back in 1995. The tuning indicator is very cool, and I had not seen a similar indicator before (could this be a way for us to escape the clutches of the San Jian counters or the Arduinos?) The Italian ham magazine articles are great, and you can follow the rig description even if you can’t read the Italian. The pictures in in the attached drive are also very good.

I have been in touch with Mattia via YouTube: He reports that he has done other electronic projects, but he considers this to be the most interesting. He does not have a ham license — he has a Shortwave Listener license. His father was a ham: I3ZQG.

This is one of the rare cases in which the builder should — I think — be issued his ham licence purely on the basis of this build. [Continue reading for details about this direct conversion receiver…]

Readers, if you haven’t already, you should bookmark the Soldersmoke website and listen to the Soldersmoke podcast!

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11 thoughts on “Soldersmoke: Mattia Zamana’s Amazing Direct Conversion Receiver

  1. mangosman

    Direct Conversion receivers are ones in which the oscillator is at the signal frequency. The output of the mixer is the input frequency- the oscillator frequency which gives the audio directly. There is no intermediate frequency used.
    The advantage of this technique is the frequencies above and below the transmission channel become supersonic and are inaudible and easily suppressed.
    This is the technique used in the Software Designed Receivers and in most new TVs and DAB+/DRM and mobile phones.
    The oscillator is usually crystal controlled and a programmable divider is used to select the output frequency.
    CML Micro/Cambridge Consultants is the latest example.

    1. Ron F

      > “This is the technique used in the Software Designed Receivers …

      If you ignore all the ones that are not direct-conversion (e.g. SiLabs/Skyworks Si47xx series, NXP’s TEF-series tuners & single-chip receivers, etc).

      > … and in most new TVs and DAB+/DRM and mobile phones.

      Ditto – most (all? Certainly that I’m aware of; I’d be interested to know of any counter-examples) use either a separate tuner IC outputting a low or middling IF to a separate DSP uC for demodulation/decoding, or an all-in-one with a low (but not 0) IF internally.

      Amusingly, and from their own documentation, that also seems to be the case with the CMX918 tuner used in the CMX1000 module you link to – it downconverts internally to a low (but not 0) IF before being fed to its internal DACs (and out to actual demodulation & decoding in an external DSP uC). That makes it at least a *single conversion* receiver, not direct conversion…

      1. mangosman

        If you go to the link in the post, you will find it is as I say. It has a single oscillator mixer converting to a zero frequency for the carrier as do the SDR designs.
        Stop playing with semantics none of these designs including the NXP TEF chips use intermediate frequency filters such as 455 kHz or 10.7 MHz used in the Superhetrodyne design.,
        I is definitely converting the input RF frequency to a digital In phase and quadrature phase output at a near zero frequency signal. This reduces the processing speed required in the coprocessor which has to do an inverse Fourier analysis and decoding functions.

        On the block diagram the I/F means interface not Intermediate frequency.

        1. Ron F

          Alan, if you’re going to reply to me, please do me the justice of actually *reading* what I wrote before responding – not simply reacting defensively to whatever imagined mess you’ve conjured up inside your head.

          You spoke about SDRs, I responded to that – including quotes of *exactly* what you said, I’ll summarise it again, just so you can’t claim you don’t understand:

          – You wrote, in response to an article about a direct conversion receiver, that “This is the technique used in the Software Designed Receivers and in most new TVs and DAB+/DRM and mobile phones.”

          That’s rubbish. Most SDRs – especially those used TV, DAB/DRM receivers, and mobile phones – are single, or even double, conversion designs.

          – You also wrote, while still talking about direct conversion techniques, that “CML Micro/Cambridge Consultants is the latest example.”

          That’s also rubbish. Your link points to a video about the CML1000 module, which uses a tuner chip (CMX918) that is a single-conversion to a low IF (and no, I’m not confusing “IF” meaning “intermediate frequency” with “I/F” meaning “interface”). I’d suggest you do a bit of research on the module and the chips it uses…

          Everything I wrote is fairly easily verifiable by anybody with a minimum of understanding who simply does even a minimum of actual research. The statements of yours that I responded to and quoted are easily disproven by even a basic Google search…

  2. Julian Stargardt

    I want one!

    What a marvellous receiver!

    Elegant design. Elegant fit and finish. I like the big power transformer too.
    Splendid reception.

    Well done Mattia!

    Tanti Auguri

    1. Jock Elliott

      Me too!

      It’s gorgeous in a very functional way.

      You look up “wow” in the dictionary and it says “see also Mattia’s direct conversion receiver.”

  3. Egil Ingebrigtsen

    Congratulations on a very impressive result! I did never achieve making such stable oscillators myself!
    Downloaded the two PDFs describing this amazing receiver. (Links found on the Soldersmoke blog).
    I don’t understand Italian, but the schematics found in the article are well worth studying. Packed with good ideas. Haven’t done any similar construction for more than ten years, but must admit that watching his video and schematics, I’ve become rather tempted….

    Nice job Mattia!

    Egil – LA2PJ

  4. Mark

    Wow, thanks for sharing this, the radio looks amazing well done !

    I think there’s something special about radios with knobs and buttons and SDR can never replace the satisfaction of using a real radio.

    I wish we had radios like this to buy.


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