AVR ATMEGA + SI5351-VFO Bare PCB
AVR ATMEGA328 + Si5351 VFO Controller Board with 3 independent clock outputs (TX, RX LO, IF/BFO). Supports 1 125 MHz output, RIT function, and calibration system. Ideal for HF/VHF radio designs. Supplied as bare PCB with instructions.
AVR ATMEGA328 + Si5351 Based VFO Controller – Multi-Output Frequency Generator
This Si5351-based VFO (Variable Frequency Oscillator) is a versatile frequency generation system designed for amateur radio and RF applications. It consists of two separate modules: the controller board and the Si5351 clock generator board, working together to provide a stable and highly configurable multi-frequency output solution.
The system is built around the popular Si5351 clock generator IC, capable of producing multiple independent frequency outputs with excellent stability and flexibility. It is ideal for use in transceivers, receivers, and custom RF projects requiring precise frequency control.
Output Structure
The VFO provides three independent clock outputs, each serving a specific role in a typical radio architecture:
- CLK0 – Transmit Frequency (TX Output)
Adjustable output from 1 MHz to 125 MHz, matching the frequency displayed on the controller. This is the main operating frequency for transmission or general signal generation. - CLK1 – Receive Local Oscillator (Rx LO)
Automatically calculated from CLK0 ± CLK2, used as the receiver local oscillator for proper tuning alignment. - CLK2 – IF / BFO Frequency
Configurable intermediate frequency (IF), such as 9 MHz or 10.7 MHz, but can be set to virtually any required value depending on system design.
Key Features
- 3 independent clock outputs (TX, RX LO, IF/BFO)
- Si5351-based precision frequency generation
- Wide frequency coverage up to 125 MHz
- Flexible IF selection (any frequency supported)
- RIT (Receiver Incremental Tuning) support
- High stability and low phase noise operation
- Suitable for HF and VHF applications
Controls & Interface
The system includes two push buttons and a toggle switch for simple and intuitive operation:
- Calibration Button – Used for system frequency calibration
- Function Button – Selects and adjusts IF frequency
- RIT Toggle Switch – Enables independent receiver tuning without affecting transmit frequency
RIT Function
The RIT (Receiver Incremental Tuning) mode allows fine adjustment of the receive frequency independently of the transmit frequency, with 100 Hz step resolution, making it ideal for amateur radio operation and precise signal tuning.
Calibration Procedure
The calibration process ensures accurate frequency output:
- Press the calibration button
- The system sets output to the reference crystal frequency
- Measure actual frequency at CLK0
- Adjust tuning to match measured value
- Press the calibration button again to confirm
If calibration fails, it can be reset by pressing the calibration button twice without adjustment, then repeating the process.
Applications
- Amateur radio transceivers
- SDR and superhet receiver designs
- Signal generation and RF experimentation
- VHF and HF frequency synthesis
- IF and BFO generation systems
- Educational RF projects
Compatibility
This VFO is suitable for both HF and VHF frequency ranges, making it highly flexible for a wide variety of radio designs.
What’s Included
- Bare PCB
| Title | AVR ATMEGA + SI5351-VFO Bare PCB |
|---|---|
| Category | PCB Kits |
| SKU | SB0fZ33 |
| Condition | new |
| Weight | 50.0 g |
