All Band Radio Uses Arduino And Si4730

It is getting harder and harder to tell homemade projects from commercial ones. A good case in point is [Mirko’s] all band radio which you can see in the video below the break. On the outside, it has a good looking case. On the inside, it uses a Si4730 radio which has excellent performance that would be hard to get with discrete components.

The chip contains two RF strips with AGC, built-in converters to go from analog to digital and back and also has a DSP onboard. The chip will do FM 64 to 108 MHz and can demodulate AM signals ranging from 153 kHz to 279 kHz, 520 kHz to 1.71 MHz, and 2.3 MHz to 26.1 MHz. It can even read RDS and RBDS for station information. The output can be digital (in several formats) or analog.

The radio takes serial (I2C) commands, and the Arduino converts the user interface so that you can control it. The chip comes in several flavors, each with slightly different features. For example, the Si4731 and Si4735 have the RDS/RBDS decoder, and the shortwave mode is available on Si4734 and Si4735. Confused? Page 2 of the programming guide should help. According to [Mirko], he used a 4730, but it still did shortwave with the 4735 library.

Breakout boards with the chip are just a few bucks. It appears the chip has the technical capability to receive single sideband, but it requires a poorly documented patch. It is in recent versions of this library, though.

We always smile when we think that AM is still alive and kicking. Perhaps this is the modern take on that first crystal radio project.

44 thoughts on “All Band Radio Uses Arduino And Si4730

        1. I have the blue version lurking in the parts stash somewhere. I think it was RadioShack/Archer. I think it maybe is a 2 part piece. Well 4, if you count the brass collet and screw in there. Will have to see if it’s near the surface. TBH I haven’t seen my tub of knobs in a while.

    1. I was about to post it was out by a factor of 10…

      The other thing that should be considered is using a 9kHz frequency step for the 520-1700kHz MW band.

      Not sure about other countries, but here in Australia they moved away from 10kHz spacing some time in the 70s.

      It’s a nice effort for a broadcast receiver though.

    1. Interest >> incentive… run a scenario… zombie black hats have taken over teh interwebs and reset and encrypted everyone’s wifi password, the only way to decode it is to decode the radio signal leaking from their equipment…

      set up. Reset your wifi password overnight, make/get a very low power AM transmitter, make a slllowww morse loop of the ROT-13 of your new password, tune it just outside of AM if you can, such that normal radios can’t get it, hide it somewhere. So make sure you have the morse alphabet printed out, all the instructions and all the parts etc.

    1. Fairly unlikely, the DSP inside has limited amount of user configurable RAM, so you wouldn’t be able to do much fancy stuff there beyond basic signal demodulation.

      For HAM radio use it is probably better to use something like an STM32 micro for doing the I/Q demodulation (that’s what these chips do) and then any protocol decoding on top if you want a compact device. Or just use an SDR solution e.g. on a Raspberry Pi.

      These chips are pretty cool for their intended use but for HAM radio you probably want something a bit more “controllable” than a chip relying on poorly documented binary blobs to be able to demodulate anything.

  1. Still waiting for the “coulda done it with a ZN414” :-D …. anyone should know it’s doing a lot more than one of those can though, even if you digify the tuning with varicaps.

    1. I vaguely remember a circuit tyat used a 555 as a rudimentary radio. Or maybe it was the 3909 flasher. It was more novelty than practical.

      Yiu’re showing your age. I doubt the 414 is being made anymore. Nowadays it’s the MK484 (I hope I got that right), I can’t rememberif it’s a clone of the 414 or a mild imorovement, but same basic design.

      I’m surprised that IC has xisted for almost fifty years n some form.

    1. There was a kickstarter for that very thing a while back, but it was supposed to have its own display like a phone AND do GPS navigation. “The perfect survival tool”

      Of course, the kickstarter flopped due to the technical challenges to putting all that in something the size of a (for nowadays) relatively small smartphone.

  2. Not trying to be a booger or anything, but this caught my interest then I noticed it is not an *all band* receiver. unless I missed something I dont see anything continuous from 135hz to ghz

  3. Hi Mr. Williams. Thanks for referring my Si4735 Arduino Library. Actually, this Library can work on all Si47XX family. I would like to invite you and all to be a member of “Si47XX for Radio Experimenters” on Facebook. Ricardo, PU2CLR.

  4. Judging by the document AN332; Programming Guide (Si47XX PROGRAMMING GUIDE); page 2 (Table 1. Product Family Function); the Si4730 was not designed to work on SW. However, some experimenters in Brazil, including me, have confirmed that this CI works well in SW. Do all manufactured Si4730 work on SW?

    1. It’s possible that parts were downbinned if they failed some test, so the ones binned as shortwave capable would have impeccable performance, and the ones binned as not shortwave capable may have performance between horrible and acceptable, or the chance of it not working at all. However, later in a part’s life, the process gets tuned up and all the dies may be equally good, and they might continue being binned for marketing reasons. Though should a manufacturer notice this and turn out a SW product with the cheaper chip, then they might attack the lower end part with a laser to disable the features that were not advertised for that model.

  5. Once the ‘interlectual property’ to demodulate it is created (and it is) it can be mass prduced. There are different companies making such ICs, but the fact that these are mainstream targeted and not on digikey or mouser, as the derivates without DAB are, is just strange. Maybe legal issues, marketing or politics. I dont think its because of volume.

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