Digi VFO

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DigiVFO is a miniature but highly functional VFO using the MS5351M synthesized clock generator, and is based on the ProgRock2 module already produced by QRP Labs. Different firmware, and the addition of a standard rotary encoder and 0.91” I2C OLED module, facilitate the DigiVFO: A feature-rich VFO with BFO and CAT control USB interface.

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$23

The features of this kit are as follows:

  • Tiny size PCB, a little smaller than an HC6 crystal: 0.725 x 0.675 inches (18.4 x 17.1mm)
  • Factory assembled PCB, ready-to-use: assembly is just connection of the rotary encoder and OLED module.
  • 0.25ppm TCXO reference as standard; typical drift and accuracy will be less than 1Hz at 40m band, for example.
  • Output frequency range is configured to cover 1.000000 MHz to 99.999999 MHz.
  • Supports direct conversion receivers, including with 90-degree quadrature phase LO
  • Supports superhet with low-side or high-side LO injection
  • For superhet radios, also generates the BFO with configurable frequency
  • Configurable CW receive offset (CW or CW-R), if you ground an input pin to indicate you are in CW mode
  • RIT (Receive Incremental Tuning)
  • VFO A / B / Split mode
  • CAT control interface via built-in USB to Virtual COM Serial port (micro-USB connector)
  • CAT via separate USART port for 3.3V logic level serial (e.g. other microcontroller)
  • QRP Labs Firmware Update (QFU) bootloader for firmware updates

Assembly is simple. The rotary encoder is soldered directly to pads on the PCB, which is hardly larger than the rotary encoder itself. 4 wires connect the OLED. 

DigiVFO can be used in multiple ways. It can be used as the VFO and BFO of a superhet (BFO frequency is configurable). Or just the VFO. Or use it as the VFO of a Direct Conversion receiver. It even has quadrature output (90-degree phase shifted outputs on two output pins) to directly drive a Quadrature Sampling Detector type mixer (a.k.a. Tayloe Detector). CAT control via the built-in USB Virtual COM Serial port makes it easy to interface with PC software; CAT commands can also be issued by a microcontroller host via the onboard USART port. 

Kit contents

  • PCB (same PCB is used for ProgRock2 and DigiVFO).
  • Rotary encoder.
  • 0.91" OLED display module.
  • 50cm of 0.33mm enameled copper wire for connecting PCB to OLED.

Documents and resources

Manual - version 1.00 (released 20-Dec-2025)

Firmware version history

Please refer to the manual for the firmware update procedure, which is very easy and does not require any special hardware, software, drivers etc. It requires only a PC and a USB cable. Click the file in the first column of the table below, to download the firmware file of interest. Note that firmware files are encrypted and can only be used on the QRP Labs ProgRock2/DigiVFO board. 

Firmware version history:

Version Date Contents
1_00 20-Dec-2025 First firmware version

Photographs