Si4735 SSB Receiver Controlled by Arduino

Build a complete LW, MW and SW (AM and SSB) radio with the Si4735 / SI4732 and Arduino.

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It is a receiver based on CI Si4735 or SI4732 controlled by Arduino with SSB support (amateur radio) conetroled by Arduino. This receiver uses the "Si4735 Arduino Library" written by PU2CLR (Ricardo Lima Caratti) and also can be used by others host MCU like (ESP32 and STM32).
1. Encoder to tune stations;
2. Band selection via push buttons
3. AM, FM and SSB;
4. LW, MW and SW;
5. Bandwidth filter;
6. BFO Control;
7. VFO/BFO switching via encoder push button;
8. 12 SW bands + one from (100KHz to 30MHz).
9. Frequency step switch (1, 5, 10, 100 and 500KHz KHz);

More detail about this project you can see on Si4735 Library for Arduino

A brief history of the PU2CLR SI4735 Arduino Library

  • 1
    Tips to build

    * Install the "Si4735 Arduino Library" on your Arduino IDE (see;

    * Use SI4732-A10 or SI4735-D60 if you want to listen to SSB mode;

    * Try to follow what the Silicon Labs recommends; * Start building the minimum circuit and test it;
    * Check if the Si47XX RESET pin (15 on SSOP version or 5 on QFN version) is connected on your MCU (Arduino) pin defined as RESET the (the most of schematics and examples of this project this pin is the digital pin 12);
    * Use the minimum sketch to test the minimum circuit. The first three examples of this project (see examples folder) can be used to test the minimum circuit; * Try not improvising the I²C bus connection. Start using a 3.3V MCU (Arduino Pro Mini 8MHz or DUE, ESP32 or other 3.3V device) to connect with SI4735;
    * Some devices provide internal pull-up resistors that in some cases can be enabled or disabled. Also, the capacitance of the I²C bus is another variable that have be considered to select the right resistor values. However, that capacitance is not easy to be measured. For these reasons, it can be a liitle dificult calculate the right resitor values at first. That said, start with a high pullup resistor to I²C bus and then reduce it until the best value. For example: start with 10K and try to reduce the value to 4,7K, 3,3K, 2.2L etc. Select the lowest resistor you can.
    * I²C bus devices are available in different speeds. If you are using an I²C display device, check if its speed is compatible with the Si47XX and also with the current speed used by the master MCU;
    * Using different voltage levels between I²C devices can be unsafe and can destroy parts connected on I²C bus, specially the Si47XX;
    * It is important to wire all your I²C devices on the same common ground. * If you are using Arduino Mini Pro, ONU or similar, pay attention to the pin 13 and the use of internal pull-up resistor. This pin has a LED and a resistor connected on the board. When this pin is set to HIGH the LED comes on. If you use the internal pull-up resistor of the pin 13, you might experiment problem due to the drop voltage caused by the LED circuit. If this occurs in your project, change the circuit to use external pull-up on pin 13. * Use only batteries to power your circuit. Receptions in LW, MW and SW can be seriously harmed by the use of power supplies connected to the grid. * See some Shortwave antenna configuration on [Si47XX ANTENNA, SCHEMATIC, LAYOUT, AND DESIGN GUIDELINES; AN383](

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Dr. Cockroach wrote 03/04/2020 at 15:13 point

That has a very nice sound to it. Can it tune in less than 1 KHz steps?

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Rene wrote 03/04/2020 at 05:54 point

Super, nu nog schematic, parts??

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Dan Maloney wrote 02/28/2020 at 20:31 point

This is interesting to me. I've been trying to find a chip that'll let me build a simple FM-only receiver for the 2-meter ham band. I thought Silicon Labs would offer something, but everything they have that can demodulate FM is limited to the broadcast band. I'd need to find a way to stretch that up to 144 or so.

Nice build, BTW

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Ricardo Lima Caratti wrote 03/02/2020 at 13:53 point

I’m not sure if the Si4735 is appropriated for that.  I think it can be used as second IF stage.  Some commercial receivers based on this CI work on Air Band (AM) (example XHDATA-D808).  I think that approach could be used for 2 meters FM.

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Dr. Cockroach wrote 02/28/2020 at 12:25 point

Wow, we just posted our radio projects minuets apart and tech wise many years apart :-)

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Ricardo Lima Caratti wrote 03/02/2020 at 13:54 point

Nice project. 

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