Posted by
Vic K2VCO on
Sep 20, 2006; 3:17pm
URL: http://elecraft.85.s1.nabble.com/Hearing-CW-Fundamental-Keying-Waveform-tp393945p393953.html
Dan KB6NU wrote:
> This discussion is very interesting to me. I hate copying stations whose
> keying isn't sharp enough. The dits and dahs seem to blend together. It
> seems to me that with all the DSP power that modern rigs have, there
> should be a way to "sharpen up" a CW signal to make it more
> intelligible.
Modern rigs all have rise/fall times between about 2 ms. (which produces
a quite clicky and too-broad signal) and about 8 ms. I think the
current K2 is maybe 5 or 6 ms. At keying speeds below about 50 wpm,
there should be absolutely no problem with the elements seeming to blend
together.
Also keep in mind that regardless of the actual rise/fall times of the
signal, high selectivity (< about 500 Hz.) starts to noticeably soften
what you hear. There are schemes that regenerate a CW signal
(basically, use the received signal to key a local oscillator or it's
possible to simply clip a signal if the s/n ratio is reasonable in order
to sharpen it up. But this doesn't seem to be especially helpful at the
usual speeds.
I'm not sure what characteristic you're describing that makes CW hard to
copy, but I don't think it's the shape of the keyed envelope.
--
73
Vic, K2VCO
Fresno, CA
http://www.qsl.net/k2vco_______________________________________________
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