SI473x Receiver Firmware Update and Internal Photos

Many thanks to SWLing Post contributor, Robert Richmond, who writes:

Hi Tom,

Ricardo (PC2CLR) recently published an excellent firmware update for the SI473x kit-based receivers flooding AliExpress, eBay, etc.

I purchased a preassembled SI473x model, and it has a much better user interface following the update IMO. Other changes include being able to tweak or disable soft mute, finer grained attenuation, and a few options being moved to the encoder instead of multiple button presses.

The update including directions and a list of features can be found here:

Best Regards,

Robert Richmond

Internal Photos

Robert also kindly shared the following internal photos of the SI473x receiver:

Robert, thank you so much for sharing the information and your SI473x photos/mods!

Spread the radio love

13 thoughts on “SI473x Receiver Firmware Update and Internal Photos

  1. Rob

    Does anyone know if you can adjust the display readout to read frequency correctly?

    My ATS-20 was pretty close when it arrived on SSB, within 100 Hz, but is now off 2.5 kHz. It’s only a week old now. I am on firmware 2.1.3. I also re-loaded it.

    Thanks for any thoughts on this.

    Also what does the S:25 on the right hand side mean under the Step.


  2. Georg Beckmann

    I bought such a receiver and also ordered some unpopulated from
    I wonder, if someone has a schematic of this board.
    I can make it from the pcb, if there is no other way, if anything eles fails.

  3. Robert Richmond

    Firmware is up to v3.0.7b if you manually download the latest repository and add the sketch to Arduino IDE.

  4. Joel Caulkins


    The Diodes on the antenna input were unnecessary. If you look behind the antenna switch there is a empty set of pads with nothing soldered, this is for a CM1213-01 static suppression chip. I bought a bunch of them off a eBay seller and installed them on all 5 of my sI47XX based radios including the one you have. They are tiny but pretty easy to install. Enjoyed all your pictures, thanks.


    1. Robert Richmond

      Welcome for the photos.

      I noted the ESD chip when skimming the data sheets. 🙂 Problem for me is soldering it.

      Reasons aside, soldering through-hole components and larger connectors are about the limit for hands anymore, and even then those can be tough at times.

      1. Joel

        I know what you mean, I don’t drink coffee before I’m going to solder SMD stuff and I have to steady my arm on the bench while soldering, oh and holding my breath helps too?.


  5. Mark

    I’ve heard some of these radios on SSB and they suffer from the same poor audio and distortion that the Tecsun DSP radios suffer from, though the audio itself didn’t seem as muddy as on the PL-990x for instance the distortion was still there.

    Tecsun’s PL-330 is actually one of Tecsun’s better sounding radios on SSB because the 4khz filter actually works, shame they couldn’t get the 990x to sound as good.

    I think the age of portable radios is over, at least for SSB, So I ordered the malachite directly from Georgiy, he has an improved version available to order now. This is the way Tecsun should be going but they will continue to sell portable radios that hardly change with each “update” for many years to come thinking that the audio on SSB is acceptable. The PL-680 is a far better sounding radio, it may lack the filtering but what good is the filtering if the sound quality is rubbish ? it’s not unique to tecsun either pretty much every portable radio that’s unfortunate enough to have the same DSP suffers the same though apart from the PL-330 the rest of the Tecsun DSP radios seem to sound the worst out of all the DSP radios.

    What’s worse is that there’s a whole lot of People that might think this poor audio on SSB is somehow normal, who may never have heard ECSS on an analogue radio or SSB in general on say the likes of the PL-680 or one of my favorite radios, the Yaesu FT-891 which has really exceptional audio quality with headphones. There’s a lot of People who may never even hard what proper SYNC sounds like.

    1. Robert Richmond

      I suspect there is a non-zero chance the SSB patch for the radio was pulled from Tecsun firmware.

      It is not replacing my desktop receivers anytime soon. 😉 That said and given its small size, it is currently setting atop my Kenwood R-2000 as a secondary receiver and for occasional FM background music.

  6. Robert Richmond

    Apologies for the typos. To think I used to be an editor…. o.0

    Perhaps the biggest problem I spotted right off is the lack of any real matching for the included whip antenna. Silicon Labs provides the recommended values in the 473x data sheets assuming someone wanted to improve reception on the whip.

    My solution? Forget the whip, attach a suitable outdoor antenna, and let outright antenna gain versus the small whip overcome the mismatch for HF and lower.

    I added power rail caps to potentially help stabilize the Nano clone, though I am not sure they really are needed. I remember comments about questionable stability, but my radio seemed stable anyway.

    The reversed diodes and resistor were added for very basic ESD protection. I suggest adding some type of ESD protection regardless if using the whip or whatever external antenna. Otherwise there are only SMD caps between the BNC antenna port and the 4732 receiver chip.

    Mods aside, the little radio is interesting for ~$60. I am listening to a FM station on mine as I type this post. It is not a Belka, but it does pack lots of features into a tiny footprint and an affordable price point.

    Would I recommend it for a first-time SWLer wanting a affordable portable? No. Instead look at a Tecsun PL-330 or similar. However, it could suffice as a project radio for someone wanting to tinker with the hardware and/or firmware.

    My biggest annoyance so far is a rather high audio highpass in SSB mode. It is fine for typical voice comms, but listening to music leaves much to be desired.

    1. Robert Richmond

      BTW, yes, my soldering “skills” are horrid. One the plus side, the radio still worked when I was done.


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