Build an All-Band Radio with Si4730 & Arduino Nano – LW, MW, SW, FM

Necessary tools and machines

Soldering iron (generic)

Apps and online services

Arduino IDE

About this project

When you mention Arduino radio, you always think of modern FM radio (88-108 MHz in Europe). The LW, MW and SW band cover the range from 0.2 to 30 MHz. SW is especially interesting. Radio waves in the shortwave band can be reflected or refracted from a layer of electrically charged atoms in the atmosphere called the ionosphere. Thus shortwave radio can be used for very long distance communication, sometimes entire continents or beyond.

Below I will present to you the development of a radio that covers all the bands mentioned above. The "heart" of this radio is Si4730 IC from Silicon Labs which can be purchased from AliExpress in the form of a small development board for a few dollars.

This board is controlled by an Arduino using the I2C protocol. The code is written by Julio C. Rosa, and is based on the Si4735-I2C-R4 library given below along with the code and scheme. Although the manufacturer says that this chip (Si4730) it is only for AM / FM, it actually works in SW too. For audio output I use mini digital amplifier board 2*3W PAM8403 Class D which is very cheap and functional.

The device is assembled in a suitable housing and represents a complete small World Band radio. Otherwise I live on the ground floor in a relatively densely populated area and use a ten meter long antenna, so the reception is pretty weak, but still comparable to commercial quality pocket radios I own.

And lastly to mention that this chip is used by many well-known brands of portable radios such as TECSUN, DEGEN, SANGEAN and others.

Code

• Code
• Libraries

CodeC/C++

/**************************************************************************************************
  JCR Si4730/5 Receiver LW/MW/SW/FM - Version to share. See schematics for wiring details.
  Written by Julio C. Rosa - The CesarSound - May/2019

  Commands:
  radio.volumeUp(); radio.volumeDown();radio.seekDown(); radio.seekUp(); radio.mute(); radio.unmute();
  radio.setMode(FM); radio.tuneFrequency(9490); radio.getStatus(); radio.getVolume(); radio.getMode();
  radio.getMute(); radio.toggleMute();
  RSQMetrics rsq; radio.getRSQ(&rsq); (rsq.stereo); print_number(rsq.stereoBlend); print_number(rsq.SNR);
  (rsq.seekable); print_number(rsq.RSSI);
  print_mode(); print_station_freq(); print_volume(); print_mute(); print_home();
  radio.getCallSign(callSign); printp(rds1); Serial.write(callSign); radio.getProgramTypeStr(programType);
  Serial.write(programType); (rds1); (rds2); (rds3); (rds4); (rds5);

*****************************************************************************************************/

// Library
#include <Si4735.h>
#include <LiquidCrystal.h>
#include <rotary.h>
#include "Wire.h"

// I/O Settings
Rotary r = Rotary(2, 3);
LiquidCrystal lcd(12, 13, 7, 6, 5, 4);

const byte band = A0;

// Variable setting
unsigned int freq = 880;
unsigned int freqmax = 10800;
unsigned int freqmin = 50;
unsigned int fstep = 10;
unsigned int freqold;
unsigned int buttonstate;
unsigned int count = 15;

// Create an instance of the Si4730/5 named radio.
Si4735 radio;

void setup() {
  lcd.begin(16, 2);

  PCICR |= (1 << PCIE2);
  PCMSK2 |= (1 << PCINT18) | (1 << PCINT19);
  sei();

  //Pushbutton seletor de bandas
  pinMode(band, INPUT_PULLUP);

  // Initialize the radio. Possible modes are AM, FM, SW, LW.
  radio.begin();
  radio.setMode(AM);

  command_am();

  // Set the initial Frequency
  radio.tuneFrequency(freq);

  lcd.setCursor(0, 2);
  lcd.print("JCR Multiband Rx");

  lcd.setCursor(0, 0);
  lcd.print("F>>");
  lcd.setCursor(3, 0);
  lcd.print(":");
  lcd.setCursor(13, 0);
  lcd.print("kHz");
}

// Encoder Interrupt
ISR(PCINT2_vect) {
  unsigned char result = r.process();
  if (result) {
    if (result == DIR_CW) {
      freq = freq + fstep;
      if (freq >= freqmax) {
        freq = freqmax;
      }
    }
    else {
      freq = freq - fstep;
      if (freq <= freqmin) {
        freq = freqmin;
      }
    }
  }
}

void loop() {
  if (freqold != freq) {
    tune();
  }
  freqold = freq;

  lcd.setCursor(5, 0);
  lcd.print(freq);
  lcd.print("  ");

  buttonstate = digitalRead(band);  // Seletor de bandas
  if (buttonstate == LOW) {
    inc_preset();
    while (digitalRead(band) == 0);
  }

  // Medidor - S-Meter (dBu) e SNR (dB) - uncomment if want to use
    RSQMetrics rsq;
    radio.getRSQ(&rsq);
    lcd.setCursor(0, 2);
    lcd.print("dBu: ");
    lcd.print(rsq.RSSI);
    lcd.setCursor(9, 2);
    lcd.print("dB: ");
    lcd.print(rsq.SNR);
}

// Presets INC
void inc_preset() {
  count++;
  if (count > 15)
    count = 1;
  bandpresets();
  delay(100);
}

// Presets Seletor de Bandas
void bandpresets() {

  lcd.setCursor(0, 0);
  switch (count)  {
    case 1:
      freq = 370;
      radio.setMode(LW);
      radio.tuneFrequency(freq);
      command_am();
      fstep = 5;
      lcd.print("LW1");
      break;
    case 2:
      freq = 620;
      radio.setMode(AM);
      radio.tuneFrequency(freq);
      fstep = 5;
      lcd.print("MW1");
      break;
    case 3:
      freq = 840;
      radio.setMode(AM);
      radio.tuneFrequency(freq);
      fstep = 5;
      lcd.print("MW2");
      break;
    case 4:
      freq = 3700;
      radio.setMode(SW);
      radio.tuneFrequency(freq);
      fstep = 5;
      lcd.print("SW0");
      break;
    case 5:
      freq = 4985;
      radio.setMode(SW);
      radio.tuneFrequency(freq);
      fstep = 5;
      lcd.print("SW1");
      break;
    case 6:
      freq = 6010;
      radio.setMode(SW);
      radio.tuneFrequency(freq);
      fstep = 1;
      lcd.print("SW2");
      break;
    case 7:
      freq = 7200;
      radio.setMode(SW);
      radio.tuneFrequency(freq);
      fstep = 1;
      lcd.print("SW3");
      break;
    case 8:
      freq = 10000;
      radio.setMode(SW);
      radio.tuneFrequency(freq);
      fstep = 5;
      lcd.print("SW4");
      break;
    case 9:
      freq = 11940;
      radio.setMode(SW);
      radio.tuneFrequency(freq);
      fstep = 5;
      lcd.print("SW5");
      break;
    case 10:
      freq = 13710;
      radio.setMode(SW);
      radio.tuneFrequency(freq);
      fstep = 5;
      lcd.print("SW6");
      break;
    case 11:
      freq = 15400;
      radio.setMode(SW);
      radio.tuneFrequency(freq);
      fstep = 5;
      lcd.print("SW7");
      break;
    case 12:
      freq = 17560;
      radio.setMode(SW);
      radio.tuneFrequency(freq);
      fstep = 5;
      lcd.print("SW8");
      break;
    case 13:
      freq = 21505;
      radio.setMode(SW);
      radio.tuneFrequency(freq);
      fstep = 5;
      lcd.print("SW9");
      break;
    case 14:
      freq = 27015;
      radio.setMode(SW);
      radio.tuneFrequency(freq);
      fstep = 5;
      lcd.print("CB1");
      break;
    case 15:
      freq = 9700;
      radio.setMode(FM);
      radio.tuneFrequency(freq);     
      fstep = 10;
      lcd.print("FM1");
      break;
  }
}

//Sintonizador - tuner
void tune() {
  radio.tuneFrequency(freq);
}

//Commands soft mute off / AVC max gain
void command_am() {
  radio.setProperty(PROP_AM_SOFT_MUTE_MAX_ATTENUATION, 0); // 0 (OFF) - 63
  radio.setProperty(PROP_AM_AUTOMATIC_VOLUME_CONTROL_MAX_GAIN, 0x3A98); // 1000 - 7800
}

LibrariesC/C++

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Schematics