[CW] Good Sounding Sidetone or Code Practice Oscillator Kit

[pa0wv]

David,

I downloaded the track.

It sounds good, BUT

The slope takes 18 ms. That means that the minimum dit length is 36 ms, 
because for shorter dits the trailing slope starts earlier then the 
leading slope ends.

Dits of 36 ms means for that reason that the max speed is 33 wpm.

Furthermore some additional remarks:

The author wrote that his carrier of 680 Hz is not phase continue but 
starts with each dit and dah with zero phase. He claims that will 
additional degrade clicks.

That is not true. Morsecode is AM 100% modulated om the carrier of 680 
Hz. With a string of dits, at 33 wpm you got a sinewave envelope when 
the slope is 18 ms, hence only two sidebands at 680 plus and minus 27.8 
Hz. However when you start each dit with zero phase you get additional 
phase jumps in the signal which widens the spectrum.

There can not be advantage of zero phase starting, because you add 
unnecessary phase modulation on the carrier of 680 Hz.

Furthermore: He produces a sinewave with a set of resistors in the range 
R up to 128 R

When those resistors are 5 percent the 5% of the largest (128R) is 6 
times larger than the smallest resistor (R) in nominal value is.
When you pass digital level 01111111 to 10000000 which is only the step 
of decimal 127 to 128 you get a spike in the output that ruins your 
sinewave and also your slope, with 10% of the max amplitude in worst 
case with 5% resistors

So those resistors have to be carefully matched up to 0,04%, and I 
suspect that a R-2R network which contains only resistors R and 2R is a 
much better choice, but still requires matching.

PA0WV