nanoBeacon: a simple personal CW beacon

There are times when you wonder if your receiver and antenna are really working as they should. The band is dead, or empty, it’s the middle of the day, the D-Layer is sponging up every radio frequency excitation. Perhaps you can hear a few signals, but they are fleeting — and you need a steady and predictable signal source for a proper test. An RF signal generator will give you a steady carrier, but there are times when you’d prefer to have a true CW beacon to tune onto. This simple, general purpose multiband CW beacon can be run up on the frequency (or frequencies) of your choice, is powered on a 9V transistor radio battery, and can moved to attenuate to the desired signal level, for radio receiver system testing purposes.

This beacon transmits a hard-coded message in morse code on any frequency supported by the si5351 (10kHz to 160MHz). The code targets an Arduino Nano, Uno or bare ATMega328P and an si5351 breakout board. No display is necessary. You can add one, and controls, if you like. The code includes a simple CW keyer for manual sending (not used, but left in place for this application).

Any number of frequencies in the HF and VHF range can be specified by adding them to an array of transmit frequencies. The beacon iterates over the array and transmits the message on each frequency in sequence. The beacon’s CW speed is configurable. Sidetone is available as a 5v square wave on the D7 output. There is no support for switched low pass filters but this would be easy to add.

The Github repository is here.

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4 thoughts on “nanoBeacon: a simple personal CW beacon

  1. nodzie says:

    Hi Paul,
    Fantastic little unit, great for receiver testing. Also liked the video about the universal arduino vfo/breakout board. You don’t happen to have one of those boards spare/available for sale do you?
    Chris, VK3TUB


    • Paul Taylor says:

      Hi Chris, I just noticed this comment, thought I had replied but maybe that was to a similar question somewhere else. I’ve used or shared all of the initial set of 5 boards from last year. I was planning on ordering a second batch with a few eerors fixed. But JLCPCB ran out of ATMega328Ps as a result of the chip shortage, so the project stalled for the time being. regards Paul VK3HN.


      • Anonymous says:

        I noticed that jlcpcb ran out of the atmega328p, have you tried futurlec? I managed to source a couple from them, although they weren’t smd


      • Paul Taylor says:

        I have purchased from Futurlec in the past, I sometimes have checked them for older or hard to find parts, I think they had IR2110 gate driver ICs when I couldn’t find them elsewhere. I see LCSC (JLCPCB’s supplier for in-house assembly) is out of ATMega328 40 pin DIL but has stock of the MSSOP ones. Thanks for the reminder.


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