![]() ![]() ![]() Also, many are not using proper timing between elements, characters, and words. However, as I quickly found, many operators use very non standard Morse transmitting techniques altering the speed of the CW throughout the QSO and not matching the other station. This seems to work very well with clean CW. This method was used both in RSCW and Morse2txt programs. An AGC function then samples the energy within the filter bandwidth and auto adjusts to isolate tone on and tone off amplitudes. ![]() My decoder uses signal processing techniques instead and filters the selected passband, applies a window function, then performs a FFT on the short sample period (about 5ms each) and uses the peak signal within this passband. Several of the Arduino based Cw Decoders work this way. Most of the simple CW decoders today do something similar but they use a tone detection IC ahead of the microcontroller. The key was the auto speed adjust I did in software. The output of this circuit was a very clean TTL tone for which I sampled and decoded based upon element durations. Years ago, in my Cw Decoder I used a circuit published in QST which was basically a narrow active filter followed by a simple PLL circuit which would lock on the CW tone. ![]()
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