[Elecraft] K2 Rev B Internal Keyer

[Larry Benko]

Please excuse me for the long winded posting:

Well I have finally finished K2 #3085 (a little late due to job
change) and have made 200 CW QSOs with it.  Upon firing up the K2
I immediately noticed that the CW keying was "heavy".  Changing
the "DOT Menu" from the default 1.10 to 0.90 helped considerably
but QSOs with several very proficient CW operators at speeds above
35 WPM resulted in comments that my CW had some variability to it.
I decided to make some measurements with the K2/KPA100 running 50W
into 40dB directional coupler and dummy load.  The measurements were
made on 21.05MHz with a 500MHz Tektronix storage scope on the
coupled port of the directional coupler.

The formula for "correct" CW is based on the standard word "PARIS"
which is 50 dot times long.  The formula for dot time = 1.2 / WPM.
E.g. @ 10 WPM the dot time = 120msec., @ 20 WPM the dot time = 60msec.,
and @ 30 WPM the dot time = 40msec.
The space between the dots and dashes should be 1.0 dot times and a
dash should be 3.0 dot times long.  Having said all this, sometimes
for waek signals or QRP a slightly longer dot time and slightly shorter
space may enhance readability.

The following measurements were made with the K2 internal set to
30 WPM which should produce dot times and spaces 40msec. long and
dashes 120msec. long for correct CW spacing.

DOT MENU setting = 0.90
Dot time = 38 - 45 msec.
Space = 34 - 39 msec.
Dash time = 111 - 119 msec.

DOT MENU setting = 1.00
Dot time = 43 - 48 msec.
Space = 32 - 35 msec.
Dash time = 114 - 120 msec.

DOT MENU setting = 1.10
Dot time = 47 - 51 msec.
Space = 30 - 33 msec.
Dash time = 118 - 125 msec.

DOT MENU setting = 1.20
Dot time = 50 - 55 msec.
Space = 30 - 33 msec.
Dash time = 124 - 128 msec.

DOT MENU setting = 1.30
Dot time = 53 - 57 msec.
Space = 30 - 33 msec.
Dash time = 126 - 131 msec.

DOT MENU setting = 1.40
Dot time = 56 - 60 msec.
Space = 30 - 32 msec.
Dash time = 130 - 138 msec.

The variability in the intervals sppears to remain nearly constant
at all speeds and is most certainly dur to the microcontroller
having other tasks to do besides CW keying.  However at higher
speeds this variability becomes a significant portion of the entire
dot interval.  This is what I believe was meant by the comments
about my CW keying variability.  Also please note that all the
adjustments result in keying that is heavy but 0.90 is pretty close
to correct.  Just for grins the following data was for my external
Logikey K3 keyer driving the K2 at 30 WPM.

Logikey K3 @ 30 WPM
Dot time = 40 - 41 msec.
Space = 39 - 40 msec.
Dash time = 122 - 123 msec.

I hope that I am missing something here or are all the menu settings
for CW timing except 0.90 (and perhaps 0.95 & 1.00) not ever proper
to use if you want well spaced CW?  I did not run all the above data
for several speeds but I did look at the RF output for the 0.90
setting at various speeds and it is reasonably close to correct.
For now I will be using an external keyer.  Thanks for the bandwidth.

73,
Larry Benko, W0QE