I think the fact that Elecraft can use around 4ms and get a crisp, yet
completely click-free, keying unfortunately
means that the other manufacturers simply haven't bothered.
Although Elecraft would like us to think of it as a secret sauce, there is
*no magic* to minimizing the bandwidth
of on-off keying using envelope shaping. Any electrical engineer with a
college degree has learned the theory behind it
in their introductory course on digital communications. And if you have
forgotten it, it's only a Google search away,
https://en.wikipedia.org/wiki/Sigmoid_function
https://en.wikipedia.org/wiki/Root-raised-cosine_filter
Given the internal architecture of most new radios (a DSP or FPGA feeding a
DAC to create the transmitted
RF signal), a simple firmware update could implement the Elecraft approach
and apply more appropriate
shape to the keying.
Unfortunately the same goes for SSB. Among my employer's many products are
high performance transmitters for
cell towers. We use both pre-distortion and closed-loop-feedback to get
extreme linearity and purity for complex
amplitude and phase modulated signals. It's not even costly, it's "just"
digital signal processing. It actually even
saves money since you can compensate for the variations and shortcomings of
low cost components by software.
Here again, Elecraft seems to be ahead. I am probably not the only one who
has noticed the "TX SMPL IN"
connector on the back of the K4.
Björn SM7IUN
Den tis 9 juni 2020 kl 04:52 skrev Jim Brown <k9yc@audiosystemsgroup.com>:
> On 6/8/2020 1:12 PM, Jim Brown wrote:
> > They achieve rise time of about 2.5 msec,
>
> Correction from N6KR (designer) -- about 4 msec
>
> 73, Jim K9YC
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