[Elecraft] K2 w/KSB CW reverse BFO

[George, W5YR]

Good arguments can be made, and have been in other forums, that rise and
fall times affect occupied bandwidth of CW signals to a large extent,
possibly as much or more than mere keying speed.

Too much detail and math to get into here, but just keep in mind that
anything that changes fast requires more bandwidth than something that
changes slowly. That old Time-Bandwidth Product thing, ya' know . . .

If the keyed waveform were perfect square waves, you would expect a large
bandwidth occupied by all the odd harmonics of the fundamental frequency
which, in this case, would be the dot/space rate of keying. So, it is
somewhat incomplete to estimate bandwidth solely on keying rate.

I do not recall the rise and fall times implied or assumed in the ARRL
License Manual topic mentioned, but I suspect it was based on the
assumption of "good amateur keying practice" which implies fairly soft
keying aimed at minimizing clicks and adjacent-channel interference.

73/72, George    
Amateur Radio W5YR -  the Yellow Rose of Texas
In the 57th year and it just keeps getting better!
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe
K2 #489      Icom IC-765 #2349     Icom IC-756 PRO  #2121


"Wallace, Andy" wrote:
> 
> > -----Original Message-----
> > From: k6se@juno.com [mailto:k6se@juno.com]
> 
> > On CW, it's definitely an issue also.  All should be aware that even
> > clean CW signals have bandwidth -- wider when the speed is faster.
> 
> This site may answer your question. I am not up on FFT math, so I
> am not sure:
> 
> http://fermi.la.asu.edu/w9cf/articles/click/
> 
> This may boil down to the following quote from this site:
> 
> http://lists.contesting.com/_cq-contest/2000-May/038610.html
> 
> Which is...
> 
> = = = =
> 
> "Does anyone recall the factor you multiply keying speed by
> to get the approximate bandwidth of keyed CW?"
> 
>         K2XA reminded me that this was previously a question in the
> ARRL License Manual.  I checked my 1976 copy and found the following:
> 
> "With proper shaping, the necessary keying bandwidth is equal to 4
> times the speed in words per minute for International Morse Code;
> e.g. at 25 words per minute, the bandwidth is approximately 100 cycles."
> 
>         Thanks to all for the responses and I guess my memory is not
> completely gone yet!
> 
>                                                 73,  Bill  W4ZV
> = = = =
> 
> Earl continues:
> 
> > Also, most of today's modern transceivers (not Elecraft) have
> > key clicks on CW extending as far as +/-2 kHz or more from the carrier
> > frequency.
> 
> My youngest transceiver (not counting the K1) is a pre-WARC vintage solid
> state model. The K1 has really got me spoiled with its auto internal ATU.
> I was thinking about perhaps upgrading my 100W transceiver (which has
> been idle since the K1 was built) to something more modern, maybe even with
> an auto ATU as an accessory. I'd still keep the K1 for QRP fun.
> 
> In looking at many ARRL reviews of transceivers in the <$1000
> class at their website, I was astounded that they would give generally
> favorable
> reviews to rigs which had horrible CW waveforms or performance. Some had
> keying
> waveforms which clip off the ENTIRE leading dit in full-break-in mode.
> Others
> had power spikes of 2x the output power on leading dits (which could damage
> linear amps). Some just had rotten T-R delays. SHAME ON THE ARRL LAB. For
> whatever reason, we (hams) have come to ACCEPT mediocre CW performance as
> standard fare. Is it really that SSB is such a standard mode that we can't
> spend
> less than $1000 to get a transceiver that does it ACCEPTABLY, never mind
> "well"?
> 
> However, if you look at the ARRL reviews of the K1 and K2 via the Elecraft
> website (some are ARRL members-only accessible), it should not be a surprise
> that the K1 and K2 exhibit textbook CW keying. And all the users on this
> List
> know how well they perform on the air, too. So now, after doing my research,
> the 100W rig I will be buying "someday" will be the K2/100. Yes, by the time
> I am done, it will be in the >$1000 class, but at least I know my leading
> dits
> will be heard around the world...
> 
> -Andy
> KA1GTT
> (ARRL life member)
>