Thanks to the production of specialized radio chips, nowadays it is possible to make a quality multiband receiver by ourselves in a very simple way. In several of my previous videos I described ways to make such radio receivers using microcontrollers. The receiver described in this project is very simple and consists of only one specialized chip, no programming is required, no tuning is required and the receiver works great immediately after connecting the components. 

The receiver is made according to the demo schematic diagram found in the manufactirer datasheet. The heart of the receiver is the Si4825 A10 IC, which is extremely cheap, and we can get a five-piece lot for a total price of less than two dollars. 

  Despite the low price, it has excellent features and completely covers the three areas of MW, SW, and FM bands. 
  The device is relatively simple to make and consists of several components.
 - Si4825 A10  IC
 - a ferrite core coil removed from a defective portable MW radio (optional)
 - A microammeter that is actually part of an old analog multimeter
 - Stereo potentiometer 2x100k
 - Potentiometer 10K
 - Small Audio amplifier board PAM8403
 - Band switch (2x3 positions)
 - several resistors and capacitors
 - and a small speaker
  On the back of the receiver there are BNC connectors for AM and FM antenna. A crystal with a frequency of 32,768 Megahertz is mounted on the chip itself.

This project is sponsored by PCBWay). This year, PCBWayorganizes the Seventh Project Design Contest where, in addition to Electronic and Mechanical Project,  also has been added a new category: STM32 Project. For the best selected projects are provided rich prizes in cash, coupons and special gifts. Submit your project for participation in this Contest from 2nd, Sep, 2024 to 19th, Jan, 2025. For more details and instructions visit the given page. Let PCBwayalways be your first choice.

 Band selection is done with a switch that actually forms a voltage divider, and the given resistances cover the following frequency ranges:

      AM from 510 to 1710 KHz
      SW from 5.9 MHz to 18 MHz
      and FM from 87 to 108 MHz
  The frequency is selected using a two potentiometers in a way that changes the voltage between the Tune1 and Tune2 pins. 

 100k potentiometer is for coarse tuning and 10k for fine tuning. The other channel of the 100K stereo potentiometer is connected through a series-connected trimmer potentiometer of 10K to the microammeter that serves as an analog radio scale.  The method of connection is presented in the diagram, whereby we adjust the trimmer potentiometer to enable a full deflection of the arrow when the tuning potentiometer is in the extreme right position. 

 I still have to mark the scale with appropriate bands and frequencies, but even this way there is enough visibility. The audio output of the Si4825 is connected to the input of a small audio amplifier to which a suitable speaker is connected. On both sides of the instrument I placed warm white LEDs for better readability of the scale.  It is important to mention that 5V is connected to the input of the radio, and the Si4825 chip should be powered with a maximum of 3.3V.

  For this purpose I used the simplest way to reduce the voltage using three series connected silicon diodes, as shown in the picture. 
 And now let's see how the device works in real conditions: First we need to connect a suitable antenna, and then immediately after switching on, the scale takes the given position which depends on the resistance of the scanning potentiometer. Analogous to the rotation of the potentiometer, the needle of the instrument is also moved. Then we select the desired band, set the audio volume, and we can start dialing stations.   I should also mention that the...