[Elecraft] Straight Key on my K2

[Kevin Schmidt]

Don Wilhelm <w3fpr at earthlink.net> wrote:
>The real problem is due to contact bounce at the key contacts.  The firmware
>cannot detect the closure on both the dot and dash lines at the same time,
>but when one is detected, the other is checked to see if it is closed too -
>now if the contacts are bouncing, at the exact time the opposite line is
>checked, it occurs at a time that just happens to be during a higher voltage
>part of the bounce cycle.
> ...


I found the suggestion by Ed, KG4ARN (listed on LA3ZA's mods page)
http://www.ac6rm.net/mailarchive/html/elecraft-list/2003-06/msg00979.html
to add a 0.1 microfarad capacitor across the straight key or bug worked
for me.

The time constant for the paddle lines to come back high is set by the
220 ohm resistor and 0.001 microfarad capacitors in the key lines which
gives a time constant of 0.22 microseconds. Adding the 0.1 microfarad
capacitor across the key changes this to 22 microseconds.  This seems
like a reasonable value to me since a test in the controller should take
about 2 microseconds; testing both the dot and dash lines sequentially
should complete in about 4 microseconds.

73 Kevin w9cf