Posted by
Kok Chen on
Dec 03, 2010; 3:54pm
URL: http://elecraft.85.s1.nabble.com/Fwd-New-Sherwood-report-tp5793377p5800305.html
On Dec 3, 2010, at 12/3 6:44 AM, Jan Erik Holm wrote:
> So now we have a 2 ms claim for the K3. I know I measured it to 5 ms
> but this was something like 2 years ago.
>
> What is it? Can Elecraft please tell.
Quite possibly the waveshaping is done by an FIR window. So the
design parameter may not be directly comparable to the risetime of a
first order IIR. (I hope Elecraft didn't take a shortcut and used IIR
waveshaping!)
You can of course use the 10% to 90% points as the equivalent risetime
even for an FIR waveshaping, but there are subtle difference from the
"risetime" compared to a typical RC filter, especially when the "tail"
of the impulse of the FIR is very different from a decaying exponential.
What I'm trying to say is that "2 msec" for one waveshape can produce
vastly different spectrum from "2 msec" of a different waveshape when
the standard of measurement is 10% to 90%. The portions between 0% to
10% and between 90% to 100% of the leading and trailing edges of a
pulse are probably more important that what it is doing between 10%
and 90%, which is usually a smooth function.
If hams apply a frequency domain criterion (like, say, -6 dB and -60
dB points in the spectrum envelope of a sequence of dits) instead of a
single number such as "risetime," we probably can more easily decide
which rigs are problematical in regards to keyclicks.
73
Chen, W7AY
______________________________________________________________
Elecraft mailing list
Home:
http://mailman.qth.net/mailman/listinfo/elecraftHelp:
http://mailman.qth.net/mmfaq.htmPost: mailto:
[hidden email]
This list hosted by:
http://www.qsl.netPlease help support this email list:
http://www.qsl.net/donate.html