Datong D70 mod to randomize word length
In my previous video (linked below), I repaired a Datong D70 Morse Code Tutor. A viewer asked in the comments, how to modify it to generate random word lengths, instead of the default 5-character word length. I decided to think about how this could be done and to try it.
In this video, I document my analysis and experimentation, and show you how to do this modification with no extra components. No doubt, there are other ways to do this, and certainly you could extend this modification to allow a very large degree of word lengths. Yet the solution I show here requires no extra parts, except for a switch in case you want to preserve the original default 5-character groups - it's very efficient.
In operation, the gap between N-length words may seem longer - this is because the IC4 counter is at "1" to make the gap, but subsequent next-letter clock pulses into IC4 are inhibited by the CLK INH pin 13. It takes a few cycles to allow the counter IC4 to count past "1" to resume audible characters; while in "1", the circuit makes no audible characters.
I finished my build by removing the “key” socket for a CW key and replaced it with a DPDT switch to give me default 5-character groups or “RND” (random) groups based on a 4-count (default is 5-count). This gives me word lengths of 4-12 on average.
My previous Datong D70 repair video:
• Datong D70 Morse Tutor repair