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Si4825 DSP Radio Receiver Kit

Updated on May 27, 2016

The Si4825 is a mechanical-tuned digital AM/FM/SW radio receiver IC that integrates the complete receiver function from antenna input to audio output.


- Worldwide FM band support (64-109 MHz)

- Woldwide AM band support (504-1750 kHz)

- SW band support (2.3-28.5 MHz)

- No manual alignment necessary

- Mono audio output

- Selectable support AM/FM/SW regional bands

- Automatic frequency control (AFC)

- Integrated LDO regulator

The Si4825 AM/SW/FM receivers eliminate the need for external microcontrollers, adjustable capacitors, IF filters and other discrete components. It can give a small portable exceptional selectivity and sensitivity through the power of DSP (Digital Signal Processing).

Si4820/24/25/31/35/36 Mechanically-Tuned AM/FM/SW Radio Receiver IC
Si4820/24/25/31/35/36 Mechanically-Tuned AM/FM/SW Radio Receiver IC

The Kit

A new project that uses this IC is available as a kit. Circuit diagram can be seen in the figure below. This project can receive AM, FM and eight SW bands.

This radio receiver uses three IC:

- Si4825 - DSP radio receiver

- LM4819 - AF amplifier

- LP2950-3.3, - 3.3V voltage regulator

The transistor Q1 serves as RF amplifier for shortwave signal.

Frequency ranges to be received can be seen in the table below. Depending on the position switch SW2 (pin 1 Si4825), the SW frequency range may be narrow (N) or wide (W).

Band Name
Band Frequency Range
FM (X4 - ON)
87 - 108 MHz
FM (X3 - ON)
64 - 108 MHz
AM (X2 - ON)
520 - 1710 kHz, 10 k tuning step
AM (X1 - ON)
522 - 1620 kHz, 9 k tuning step
N 3.20-3.40, W 3.20-7.60 MHz
N 4.75-5.06, W 3.70-12.5 MHz
N 5.60-6.40, W 3.90-7.50 MHz
N 6.80-7.60, W 5.80-12.1 MHz
N 9.20-10.0, W 5.90-18.0 MHz
N 11.6-12.2, W 7.00-23.0 MHz
N 15.0-15.9, W 9.50-18.0 MHz
N 17.1-18.0, W 10.0-16.0 MHz

According to the application note AN738 from Silicon Labs, these bands can be changed by right choice of resistance values R16 to R30 up.

The power supply can be made from two AAA batteries or a 5 volt power supply from a USB adapter. Also it is possible to use rechargeable batteries (1.2V, Ni-MH, AAA). In this case the group R2, R3, D5 provide charging with a low current (trickle charging). This group must be soldered only if you want to use rechargable bateries.

The radio receiver has two connectors for external antenna: AM (terminal block) and FM/SW (SMA connector).

The kit is available in two versions:

- DSP-Radio-PCB - In this version is delivered only the printed circuit. The circuit board is of high quality with the following characteristics: 150x90x1.6mm, fiberglass (FR4), green soldermask, silkscreen.

- DSP-Radio-SMD - In this version is delivered the circuit board with soldered SMT devices (Si4825, LM4819 and USB connector), the voltage regulator (LP2950-3.3) and some electromechanical devices (phone jack, SPDT power switch and battery holder).

You can download here schematics, BOM, data sheets and PCB documentation.

The price of the kit is listed in the table below. To order, deposit the amount for the chosen item to my Paypal at For any inquiry or clarification, send email to the same address. Please checking it twice your delivery address.

European Community
22 Euro
10 Euro
European Community
30 Euro
10 Euro
25 USD
14 USD
34 USD
14 USD
Gerber Files
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