Some of my projects and technical posts



The WA5BDU Keyer – An Arduino keyer that can be used in a minimal mode, or as a full-featured keyer.



An Arduino Si5351a Quadrature VFO Controller – Takes a basic Si5351a control scheme and expands it to a full-featured VFO including band changing, step size selection, CW pitch offset with a T/R input to alternate between TX and RX frequencies, RIT, USB/LSB selection and more.




Programming the Si5351a synthesizer – This page is not a construction article, but is a discussion of how registers which control the frequency and phase of the Si5351a are calculated.




An Arduino Frequency Counter – Here’s an Arduino frequency counter that uses the 74LV8154 32-bit counter IC. A simple version uses the Arduino’s clock for a time base and a more accurate version uses a HEF4521B 24-bit divider plus crystal oscillator IC to provide a 1 second time base.


An Arduino frequency counter

An Arduino frequency counter by WA5BDU       Introduction This is going to be a fairly long description of the frequency counter and the ICs and circuits that make it go. That’s for people who might want to roll their own or modify this one. Otherwise, if you’re mainly interested in building one, gloss …

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Programming the Si5351a synthesizer

  What is being discussed here   I’m going to discuss how a program, or my Arduino program specifically, calculates register values for the Si5351a to put it on a specific frequency. I’m not going into details of how the register values are formatted into bit fields and actually sent to the chip via I2C. …

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An Arduino Si5351a quadrature VFO controller

Front view of the VFO. The display is indicating the Receive and Transmit frequencies, the step size, and the current mode. Pushbuttons PB1, PB2 and PB3 are surface mount type soldered to a bit of circuit board material.   Here’s a full-featured VFO I built around the Si5351a synthesizer IC and an Arduino controller. I’ve …

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Some pages of projects or technical information   Links to pages for projects and info:    

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