Build a cw decoder.
In 1996 I had to learn cw to get my HF license.
Ronald ON7CQ then prepared several amateurs to take their exam.
This was a real torture for me and I was overjoyed that I had passed. Meanwhile, my CW knowledge is limited to recognizing individual characters here and there.
Now during the obligation to stay at home I came across a design of a cw decoder.
Have a look at: http://www.oz1jhm.dk/content/very-simple-cw-decoder-easy-build
The scheme is very simple.
This didn't work very well for me. I had to turn the volume up quite a bit.
Another disadvantage is that you interrupt the loudspeaker. So I used an extra LF amplifier.
The audio signal varies the 2.5V on the analog input of the arduino.
The decryption is done entirely in the software and is based on the goertzel algorithm.
http://en.wikipedia.org/wiki/Goertzel_algorithm
Then I saw the Budd WB7FHC decoder.
Google this call and you will find a lot of info. also in dutch.
See https://a08.veron.nl/zelfbouw/ Accessoires/cw-decoder/
WB7FHC uses a tone encoder ic , an LM567.
The circuit was built on a breadboard. (here the version of PY2OHH )
For me, this decoder worked a little better than the first.
Tuning was a bit difficult because I didn't have a 10k potentiometer. I used a 4k7 fixed resistor. Also here I had to use the extra LF amplifier to be able to tune properly.
Then I came on youtube against the design of Jim KW4KD .
https://www.youtube.com/watch?v=FaaQbMpAI1U
It uses a stronger processor. I made the maple mini version.
All info can be found on github . https://github.com/jmharvey1/STM32_CWDecoder
It also uses a microphone module so that the audio is always audible.
What is also very practical is the APA106 LED.
The color of this LED can be controlled via software.
When you hear a cw station, turn the vfo until the led starts flashing green.
If you are too high or too low, the color is red or blue.
This decoder works best for me. So I completely rebuilt it.
The schematic:
I had to make 1 change. My screen was running on 5 volts. So you should also use a 7805. You connect the 5V to Vin of the maple mini and of course to the 5V of the LED and the screen.
The maple was taped to the screen. All connections were made with dupon wires.
To be able to program the maple in the standard arduino software, some extra drivers have to be added. This is well explained on the github link.
It looks a bit messy but it works.
Here's the final finish:
The microphone sticks to the back of the box and is therefore directly in front of the external speaker.
There are a lot of E's in between but the signals were pretty weak when I took this picture.
If you press “norm” you get 2 other decoding algorithms. Since my screen is not pressure sensitive, I can't test the difference.
