Building a receiver with an SI4735 chip
I saw an article in the Razzies (journal of PI4RAZ 202009 https://www.pi4raz.nl/index.php/razzies/) a receiver with an SI4735 chip.
This ic is an RF Receiver AM, FM, LW-SW, WB 153kHz ~ 279kHz, 520kHz ~ 1.71MHz, 2.3MHz ~ 26.1MHz, 64MHz ~ 108MHz.
Mr Vadim Afonkin has written a clever piece of software so that SSB reception is also possible.
Gert PE0MGB built this receiver. He used the design of Ricardo PU2CLR for this.
This OM has created a complete library for arduino and written more than 20 versions of software.
Check out his github page https://github.com/pu2clr
I decided to build the receiver.
I first tested an ordinary 0.96” OLED screen that I had lying around.
I noticed that the letters were very small. That's why I decided to use a 1.3” screen.
I had to adjust the PU2CLR software a bit. I'm using an arduino mini pro 3.3V .
I had seen a version with an si4732 chip on the well-known internet sites.
I decided to use such a small box as well and power everything with a battery.
First I made a test pcb with my cnc machine. This also allowed me to test the modified software.
Then I designed a pcb that fits in the housing (10x10x5cm). I have provided all arduino pins with a connection so that the PCB can also be used with 1 of the other versions designed by Ricardo PU2CLR.
The readout is perpendicular to the HF pcb and is fixed on the front panel with the rotary switch.
If you look at the schematic you will see a number of switches.
Volume +, volume-, band+, band-, bandwidth, mode, attenuator and the frequency step.
The si4735 can directly control headphones. I used a TDA2822 module I had laying around to drive the speakers.
In an application note ( https://www.silabs.com/documents/public/application-notes/AN383.pdf ) you will find some extra info.
For example, I provided the coil of 180µH and the overvoltage diodes on the PCB, but did not place them.
You can buy a working device on the well-known sites for just under 50 euros.
You will miss the fun of building this yourself.
I estimate that everything cost about $30 without the case.
if you want the software or gerbers please fill in the contactform.
Have fun building this receiver.
