[CQ-Contest] WPX CW Signal Quality Concerns

Jim Brown k9yc at audiosystemsgroup.com
Sat Jun 6 18:52:00 EDT 2020

On 6/6/2020 12:28 PM, Jeff Blaine wrote:
> The responsibility lies solely with the operator.  I know this is 
> probably a quaint concept given the larger cultrial trend abrogating 
> personal responsibility, but fundamentally it's the job of the operator 
> to run his station properly.  And that includes using slow rise times 
> for rigs that provide such adjustment.

AND not using rigs without well shaped rise times. I know of two major 
companies making such rigs -- Elecraft and Flex. It's probably no 
accident that they are US companies whose managements are quite 
sensitive to our concerns.

On 6/6/2020 12:39 PM, Björn Ekelund wrote:
 > I use the 6ms setting on my IC-7610 and IC-7300

If there is a slower setting it should be used. Skip can make any of us 
very strong for others besides our neighbors.

 > Factory default PTT lead time on many radios (Elecraft particularly,
 > with 8ms) is too short for non-QSK PA.

I don't remember owning a rig without easily adjustable PTT delay. And 
I've never owned an amp for which 8ms was too short. Further, there is 
no interaction between PTT delay and keying risetime.

Keying rise time affects clicks because what we call CW is really 100% 
amplitude modulation of a carrier by a rectangular wave, which includes 
infinite harmonics whose amplitude and number are inversely proportional 
to rise time. The harmonics in the audio frequency range produce 
sidebands alike any other AM -- that's what we hear as clicks.

Slides 8 and 9 of this Power Point pdf shows the bandwidth of keydown CW 
at 2 kHz and 5kHz display width.

Slides 14 and 15 is a K3 at 25W, 5 kHz display width and a KPA500 driven 
by it. Slide 16 is the output of my Titan 425 at 1500W. Subsequent 
slides show other rigs and amps, including a MarkV, FTDX5000, and ACOM 1010.

I bought the 1010 used for CQP county expeditions because it ran on 120V 
and I hoped it would be cleaner than a solid state amp. These 
measurements show that it's not, so I sold it.

On 6/6/2020 12:44 PM, Mike Smith VE9AA wrote:
 > Will amps key differently?

Yes -- less clicks!

 >Will my CW sound soft?


 >Will leading dits be clipped?

One has nothing to do with the other.

73, Jim K9YC

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