[CW] Frank W7IS: THE REAL REASON FOR SPEED KEY DOT STUTTER

[D.J.J. Ring, Jr.]

I own way too many Mac keys... The Mac Stream keys are unique and a
hoot to use on the ham bands.

The Mac key I've tested that had the worst case of self oscillation of
the dot contact is a black based P500. McElroy might have been the
worlds best telegrapher but he certainly wasn't much of a machinist.
Some of the literature he put out stated that each key was
scientifically adjusted at the factory using Oscilloscopes !!! The sad
part is he charged extra to equip only a few deluxe keys with the dot
stabilizer he invented. Leaving such a large number of keys to suffer
from the self oscillation problem of the dot contact spring assembly.
But I'm sure he went to the grave never realizing his mistake. One of
the neat things he did on some keys was to provide a height adjustable
large dampener wheel. The dampening wheel works best by hitting the
wheel in a way that forces it slightly upwards. Its too bad all his
keys didn't provide the height adjustable dampener wheel. When Martin
invented the very first Vibroplex in 1904, he equipped it with a long
set screw to adjust the articulated damper travel. But then abruptly
dropped the feature soon afterwards.

I own a number of those very first Vibroplex's made in 1905 and 1906
and the only thing that causes them to be difficult to adjust for best
code is the main spring he used in those days were too long. And the
long main springs caused the dot arm to flop around too much on the
damper. It wasn't till around 1912 that Vibroplex started using
shorter main springs.. The type of material and length of the main
spring being critical in how the key makes dots. The highest quality
main springs ever placed on a speed key were on the WW2 Bunnell J36
keys. They take more to slow them down but produce the highest quality
code at any speed. Some keys with weak main springs cant make more
than 5 or 6 dots in a row.. and cant be adjusted to send over 25 wpm..
Below is a link to a Blog that I wrote in 2009 about my experience
with a difficult to adjust Lionel J36 WW2 speed key.. It turned out
the problem with the key was the metal arm which held the dot coil
spring in place had too much play.. So you can run into all sorts of
weird problems with vintage speed keys.

http://speedkeytests.blogspot.com/2009/02/testing-lionel-j36-ww2-speed-keys.html

Frank W7IS