26/10/2020

Dual Conversion HF Receiver 
Silabs Si4732/Si4735 and Si5351

HF RECEIVER




RF Part
  • Silabs Si4732 (Si4735 can also be used)
  • Si5351 as Local Oscillator
  • Si4732 receives at fixed 21.4 Mhz IF frequency (AM/SSB)
  • 15 Khz Crystal IF filter
  • Range 500 Khz - 30 Mhz
  • LP filter 30Mhz
  • Switchable HP filters 500Khz & 3.5Mhz 

User Inteface

  • Arduino Mini Pro 3.3V
  • OLED 1.3" SH1106
  • Rotary Encoder
  • Pushbuttons
  • 24LC256 EEPROM for storing SSB patch

Block Diagram


Using this architecture tuning is done by the LO Si5351 with up to 1 Hz resolution, and most important as the Si4732 is set at a fixed receive frequency of 21.4 Mhz, the 'chuf-chuf' sound is eliminated when tuning the bands


FRONT END / MIXER / DIPLEXER

Filter Low Pass 30 Mhz + High Pass 500 Khz

Filter Low Pass 30 Mhz + High Pass 3.5 Mhz

Diplexer





IF AMPLIFIER & 21.4 Mhz Crystal Filter

 
IF Amplifier gain 19.5dB-6dB Att = +13.5dB
(Using AD9910 RF generator and homemade RF voltmeter)

IF chain test(Using nanoVNA and atenuators)

Si4732 Receiver section

Si 4732 Receiver & LM386 Audio Amp

Construction

 

Project in enclosure



Software, Parts & Equipment used

Arduino Nano 3.3V, Encoder, OLED
https://www.monarcaelectronica.com.ar/
ADE1-ASK Mixer & Toroids
https://www.kitsandparts.com/ 
DDS AD9910 Arduino Shield RF Signal Generator
https://gra-afch.com/catalog/rf-units/dds-ad9910-arduino-shield/ 
RFSim99 (Filter design) by Stewart Hyde
https://www.ad5gg.com/2017/04/06/free-rf-simulation-software/


Special thanks for the Arduino Libraries to its authors:

Arduino Library for Si4735 by Ricardo Lima Caratti
https://github.com/pu2clr/SI4735 
Arduino Library for Si5315 by Pavel Milanes
https://github.com/pavelmc/Si5351mcu 
Arduino Universal 8bit Graphics Library by olikraus 


































































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