[CQ-Contest] WPX CW Signal Quality Concerns

Jim Brown k9yc at audiosystemsgroup.com
Tue Jun 9 14:38:52 EDT 2020

On 6/8/2020 9:25 PM, Björn Ekelund wrote:
> I think the fact that Elecraft can use around 4ms and get a crisp, yet
> completely click-free, keying unfortunately
> means that the other manufacturers simply haven't bothered.


> Although Elecraft would like us to think of it as a secret sauce, there is
> *no magic* to minimizing the bandwidth
> of on-off keying using envelope shaping. Any electrical engineer with a
> college degree has learned the theory behind it
> in their introductory course on digital communications.

Yes. I learned it in about 1963, long before anyone thought about 
digital, although not the raised cosine response.
> Given the internal architecture of most new radios (a DSP or FPGA feeding a
> DAC to create the transmitted
> RF signal), a simple firmware update could implement the Elecraft approach
> and apply more appropriate
> shape to the keying.

Prior to publishing the final version of my 2014 report, I "leaked" an 
early version to someone whom I knew would send it to Yaesu. Soon after 
I published the final version, Yeasu released a firmware upgrade for the 
FTDX5000 that significantly improved its keying bandwidth. That fix is 
dcoumented in my testing of a neighbor's rig in this set of slides.

> Unfortunately the same goes for SSB. Among my employer's many products are
> high performance transmitters for
> cell towers. We use both pre-distortion and closed-loop-feedback to get
> extreme linearity and purity for complex
> amplitude and phase modulated signals. It's not even costly, it's "just"
> digital signal processing. It actually even
> saves money since you can compensate for the variations and shortcomings of
> low cost components by software.
> Here again, Elecraft seems to be ahead. I am probably not the only one who
> has noticed the "TX SMPL IN"
> connector on the back of the K4.

It's also on my Elecraft KPA1500 power amp.

73, Jim K9YC

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