My 1998 edition shows a much different photo. I am referring to section
17.5, figure 17.52. The photo depicts an abrupt rise and a very sharp
discontinuity on the trailing edge. Likewise, the photo show in figure
15.8(a) shows the same keyed waveform in better detail.
What the ARRL Handbook fails to address is that it is not only is the
rise/fall wave-form important, but that all points between zero and maximum
output along the keyed wave's function need smooth consistency in order to
minimize bandwidth.
It been stated here before and is probably worth repeating that the actual
shape of the wave-form is more important than the measured rise/fall time.
It is entirely possible to construct a 1-2 ms rise/fall that produces less
sideband energy than a poorly-constructed 10 ms rise/fall time.
-Paul, W9AC
----- Original Message -----
From: "Mark Beckwith" <mark@concertart.com>
To: <topband@contesting.com>
Sent: Monday, January 26, 2004 11:10 PM
Subject: Topband: Keying waveform
> I have posted the photo of the CW waveform out of my handbook to head off
> any potential misunderstanding. I think at some point the ARRL probably
> started using a different photo. This one I have posted out of the 1975
> ARRL Radio Amateur's Handbook meets all of Tom's criteria:
>
> http://home.swbell.net/swca/radio/handbookcwwaveform.JPG
>
> The accompanying text claims it has 5ms rise time, and you can plainly see
> the rounded corners, er, I think? Tom, am I misinterpreting this photo?
>
> Mark, N5OT
>
>
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