Mostly DIY RF’s UDVBM-1 Is a “Universal” VFO and BFO for Radio Work — with Plenty of Extras

Pseudonymous ham radio enthusiast “Mostly DIY RF,” hereafter “Mostly,” has launched an open-hardware board designed to act as a “universal” variable frequency oscillator (VFO) and beat frequency oscillator (BFO) — driven by an Arduino-compatible microcontroller.

“I wanted to replace the drifty VFO in one of my [radio] rigs with a digital solution, but my hand-wired solution was messy, fiddly, and prone to ground loops and digital noise,” Mostly explains. “So I designed a PCB and, well, I got carried away. The result is the UDVBM-1: A universal motherboard for an Arduino-compatible microcontroller (MCU) module and an Adafruit-compatible Si5351 PLL [Phase-Locked Loop] clock module.”

The UDVBM-1 is designed to provide or replace variable or beat frequency oscillator support for a given radio, typically being used to replace both. The microcontroller’s I2C, SPI, and 1-Wire buses are brought out for additional hardware including rotary encoders, buttons, displays, buzzers, or cooling-fan control systems, and the analog to digital converter (ADC) and pulse-width modulation (PWM) capabilities are kept intact — making for a flexible add-on capable of doing a lot more than providing simple oscillation.

At the time of writing, Mostly had designed three variants of the UDVBM-1: one for the Arduino Nano, one for the Arduino Pro Mini, and one for the Seeed Studio Xiao family of microcontrollers. The Arduino models include a small breadboard area for additional hardware; the Xiao variant does not.

Mostly is selling the UDVBM-1 via Tindie at $9.95 for a bare PCB, $15.95 as a kit of parts excluding SMA connectors, or $34.95 fully assembled and tested — though still lacking the SMA connectors. KiCad project files, source code, and documentation for the project have been published to GitHub under the reciprocal Creative Commons Attribution-ShareAlike 4.0 International Public License.