[Elecraft] IMD and CW

[Alan Bloom]

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
>