Please note, the current stock is green PCB in the image only. Both green and purple PCB has same same circuit and function.

Lipo Battery operation is recommended. If with external USB power supply, please attach antenna terminal only core line of coaxial cable, it will lead better reception.

This receiver is application specified for SSB/CW amateur radio receiving. Please consider this item for shortwave and FM broadcast receiving. (actually Si4735 has a function of receiving AM/FM broad cast receiving, but the default firmware does NOT activate this function. You can focus on programming better firmware by this completed hardware?

This item includes: fully soldered and inspected radio board, BNC female connector for antenna terminal, and plastic knob for tuning shaft

What is it?

Silicon Labs Si4735 based HF SSB receiver. The Si4735 itself supports not only HF SSB, but also general AM reception and FM radio reception, but this radio is especially focusing on HF SSB mode reception, used by amateur radio.

Why did you make it?

Very recently I took an amateur radio license and got to know digital mode communication (FT8) becomes very popular. FT8 signal is modulated by SSB (single sideband) with USB (upper sideband) and it cannot be demodulated by general shortwave receiver including my other item (DSP radio version 4). In addition, I love CW (morse code) communication, but also it cannot be demodulated by general (broadcast) shortwave receiver. I know, USB dongle type SDR can easily realize super wide-band reception with multi-mode demodulation including SSB, but it requires "base" PC. I just wanted to make a "handy and independent shortwave SSB receiver".

On the other hand, very recently some people released "special code" enabling SSB reception by Si4735, and also established a very useful library. After knowing this fact, it did not take more than one week for starting my new SSB receiver project.

What makes it special?

• By nature of DSP radio, this radio fully covers HF amateur band from 1.9 MHz to 28 MHz.

• Tiny OLED display will show all information of operation.

• The firmware is fully accessible written by Arduino IDE. If you prefer 135 kHz or 475 kHz receiver making, just modify your firmware as you wish.

• Main controller is ATMega328P with Arduino Pro/Pro mini boot loader. No special development environment required. (Just Arduino IDE is enough.)

• The board has built-in USB-UART interface. Just connect USB cable is enough to change firmware as you wish.

• The board has built-in Lipo battery charger. No need to make wasted battery but just connect your single cell (3.7 V) Lipo battery enables very handy operation.

• 6 tactile switch is prepared for your custom programming. These switches are connected with Mega328P's GPIO.

• By the sake of well-written library, this radio can change reception BW from 500 Hz to 4 kHz, which is quite useful for QRM rejection.

Other functions are described in the image above.

Possible FAQ

• Does it have fine-tuning less than 1 kHz?

No, it does not. The minimum resolution is 1 kHz. Sorry about that.

• Why so expensive compared to version 4?

Simply due to the cost difference of DSP chip... You can check its price at digikey.

Before usage, please connect antenna for reception. Definitely external antenna connection is required for good SSB/CW/FT8 reception.