[Elecraft] CW rise time setting

[Alan Bloom]

In the "good old days" key shaping was done simply by adding a capacitor
to the key line or equivalent.  That results in an exponential rise
and/or fall time, which is not optimum, so the time constant had to be
set pretty slow to avoid key clicks.  Typically 5-10 ms.  10 ms results
in "mushy" keying, especially at high CW speeds. 

Raised-cosine key shaping is close to optimum and is easy to implement
with a DSP.  It allows faster rise/fall times without key clicks.  I
assume Elecraft is using something like that. 

Alan N1AL 

On 2020-06-08 12:51, E.H. Russell wrote:

> I'm used to CW rise times in th 4-7ms range. Is this 2.5ms arrived at by a
> different metric? Is the curve added by sigmoidal shaping somehow excluded
> from the measurement?
> 
> Ed / w2rf
> 
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> On
> Behalf Of Richard Stutsman
> Sent: Monday, June 8, 2020 1:31 PM
> To: David Gilbert <ab7echo at gmail.com>
> Cc: Elecraft Reflector <Elecraft at mailman.qth.net>
> Subject: Re: [Elecraft] CW rise time setting
> 
> Yes, I would regard a 2.5 msec rise time (using appropriate sigmoid
> 
> shaping) to probably be ideal, in which case I would have no desire to
> modify or shorten it. I'll bet it will sound even better than a Drake or a
> Ten-Tec!
> 
> I hereby withdraw my previous request/opinion.
> 
> Rick N6IET
> 
> On Mon, Jun 8, 2020 at 10:27 AM David Gilbert < <mailto:ab7echo at gmail.com>
> ab7echo at gmail.com> wrote:
> 
>> You don't need to generate clicks to have a crisp CW tone.  Elecraft
> 
>> uses a pretty much optimally shaped waveform (some version of a cosine
> 
>> function) and if I remember correctly the rise time is only about 2.5
> 
>> msec, although I could be wrong about that last part.  And while you
> 
>> may be careful not to use short rise/fall times when the band is
> 
>> active, in the past there have been folks on the contesting reflector
> 
>> who openly admitted they purposely generate clicks by shortening the
> 
>> rise/fall times to give themselves elbow room.  I will always
> 
>> appreciate that Elecraft doesn't give those miscreants the means to
> pollute the band.
> 
>> 73,
> 
>> Dave   AB7E
> 
>> On Mon, Jun 8, 2020 at 9:23 AM Richard Stutsman <
> <mailto:rastuts at gmail.com> rastuts at gmail.com> wrote:
> 
> I for one would like to have some control over the rise/fall times.

> 

>> You want the cleanest (narrowest) of CW signals when operating on a

>> crowded band or in a contest - unless you're a rare DX station. Most

>> of my operations are 22wpm rag chews on very uncrowded bands. We're

>> often the only discernible signals on an entire CW band. And

>> conditions are often noisy with deep QSB. Why not allow those of us

>> operating in those circumstances to shorten the rise times a bit,

>> which makes it easier to copy in noisy conditions, when any close-in

>> clicks or thumps aren't going to bother anybody? Copying a 'soft'

>> weak CW signal is like trying to read a 'crisp' signal that's an

>> entire S-unit weaker, IMO.

> 

>> My TS-590sg let's me do that, and I love it!

> 

>> Will the K4 sound as good as a Drake T4C? (Just askin'.)

> 

>> Rick N6IET

> 

> N4ZR wrote:

> 

> Will the K4 have options for setting CW rise and fall times...?

> Hi Pete,

> Probably not. We've always been very careful to ensure our rigs

> have an exceptional clean, click-free CW signal. (Third-party

> testing bears this

> out.) Minimizing the bandwidth requires a very specific rise/fall

> time

>> and

> a hand-crafted sigmoidal shaping function in DSP.

> Colonel Sanders closely guards his fried chick recipe, Mrs. Fields

> won't reveal what's in her chocolate-chip cookies, and only

> selected firmware monks--sworn to secrecy--are privy to Elecraft's

> keying envelope coefficients :) 73, Wayne N6KR

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