I believe the K3/K3S use a raised sinusoid key shaping. It is a good
compromise to reduce the bandwidth without excessive ringing/backwave.
In the bad old days, CW key shaping was typically a simple R-C filter on
the key line. That resulted in an exponential rise and fall, which
resulted in more key clicks for a given rise/fall time than a raised
sinusoid.
Alan N1AL
On 12/23/2016 01:30 PM, K9MA wrote:
On 12/23/2016 12:11, Alan Bloom wrote:
For a CW signal, the nonlinearity of a typical power amplifier should
have the effect of shortening the rise and fall times. That does
indeed widen the transmitted bandwidth. But intuitively, it seems
like the distortion would have to be really bad to shorten the
rise/fall times by much. You could always compensate for it by
adjusting the K3 for softer key shaping.
Alan N1AL
I think it's a little more complicated than that: The K3 shapes the CW
waveform very carefully, to minimize bandwidth. (I think it's
equivalent to passing the signal through a narrow bandpass filter.)
Obviously, any distortion downstream is going to compromise that careful
shaping. However, based on my intuition and Vic's results, I suspect it
would take a truly terrible amount of distortion to significantly
increase the CW bandwidth. Given that the K3 is so much cleaner than
many other popular radios, I doubt we need to worry.
73,
Scott K9MA
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