Thursday, 30 July 2015

CW decoder - Introduction

If you do follow me on twitter (and if you don’t – you really should) you will have no doubt seen my recent tweets about constructing  a CW decoder. After a number of retweets, and favorites from other very interested hams – I did promise that I would collate all my knowledge into a blog posts and share the details with you all.

So, for those who have not been following me on twitter – here is the sales pitch. I recently started looking at some projects that I could get my Arduino Uno involved in with the radio hobby. I have a number of reasons why I want to combine radio, Arduino and some electronics – more about this later.

I stumbled across a video on YouTube where Budd Churchward showed his Arduino copying and decoding CW straight off the HF band and at a reasonably high speed. I ventured further and wanted to know what electronics Budd was using to achieve this excellent little project.

I used the limited shared knowledge and discovered that the electronics is basally a LM567 – Tone decoder chip that (I have since discovered the chip is used in the ARRL book for Arduino Projects) I discovered takes an audio input and converts this to a HIGH / LOW output suitable for the Arduino to use as a signal for decoding.

Finding a suitable project for the LM567 and trying to work out how fellow constructors had configured their LM567s was not an easy task. This did indeed take quite a lot of chasing and head scratching.  I will go into more technical detail on the next post – but for the reason why I wanted to complete this ? very simple. I w
ant to create a project that would “inspire” young electronically minded students that might have an interest in radio – (i.e the morse code) some coding experience and some construction / electronic interest. This project covers all 3 areas, and only lightly covers each subject area.

In the next post – I show the LM567, the schematic and give you the list of parts required.