The Quick and Dirty Code Practice Oscillator

By Bob Hill KG5WRY

With all the excitement around learning Morse code via the Long Island CW club, it was time to collect the tools needed to learn CW. One of the tools needed for this adventure is the code practice oscillator.

The code practice oscillator is an essential component when learning Morse code. It’s the thing that makes sound when the key is pressed. The question is…where can you acquire a code practice oscillator? There are commercial solutions from Amazon or ebay. There are also a number of kits available from various sources( QRPGuys, Morserino).

555 Timer Module

If you are a maker, and want to knock out something quick, you may already have the parts to make a practice oscillator in your junk box. Using a 555 timer IC and a handful of parts you can quickly build a practice oscillator. I started looking for a 555 timer in my parts stash, but couldn’t find any.

Next stop, Amazon, for a quick purchase.

A search for 555 timers resulted in more than just ICs. I found a 555 timer module that would suffice for most of the parts of my practice oscillator. Just add a 9 volt battery, a 10 uF blocking capacitor, and a speaker and I would be in business.

Code Practice Oscillator Schematic

The circuit shows the 555 timer module along with the straight key, 9 volt battery, blocking capacitor and speaker.

Selecting the on-board 1 uF capacitor ( J1-2 to J1-7) and adjusting RV1 and RV2 to about 1K ohm each will produce a tone of about 480 Hz. The picture shows which position on the header to place the jumper to select the 1 uF capacitor on the module.

The completed prototype shows how the components were connected. It’s not pretty, but it is functional. This build was easy, quick, and functional. Try it.

Please note: The straight key is my own design.

Parts needed for this project from Amazon are:

555 timer module:

9 Volt Battery connector:


10 uF 25 volt capacitor: