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W0EB's Dot Stabilizer

For Semi Automatic (Bug) Keys

Right handed Dot Stabilizer mounted on a late model Vibroplex Original

Back in the late 1920's early 1930's, T.R. "Ted" McElroy (Morse copying World Champion) who also manufactured telegraph keys, came up with a nice innovation he called his "Dot Stabilizer" This nifty little gadget pre-loaded the vibrating dot contact spring by a very small amount, effectively ensuring better dot weighting and came very close to completely eliminating the very rapid contact bounce occuring when the contacts "break" which creates what many call "scratchy dot syndrome".

A better explanation provided by Don Haywood, WB6BEE, states that the concept of the dot stabilizer is to limit the relaxation of the spring when you release the tension. When the contact "makes", the spring tension forces good contact as the dot spring is collapsing. When the contact "breaks", the spring is losing tension, relaxing, resulting in irregular contact separation. The DS stops the spring from expanding (relaxing ) at an exact and adjustable point, and this comes very close to completely stopping that "follow on" bounce which is the root cause of "Scratchy Dot Syndrome". It does not, however correct bad CW caused by poor sending habits or failure to keep the bug's contacts clean.

T.R.'s original version required replacing the existing dot contact assembly with his stabilizer and fit only the McElroy manufactured keys. For some unknown reason, most information on the original Dot Stabilizer was either lost or ignored during the WW2 years and after except by a very few people. I'm quite happy that I was able to resurrect something from the past that does such a nice job of making a bug able to send better CW without having to severely modify a nice key.

After accidentally rediscovering it a couple of years ago, I undertook a slight redesign of McElroy's original device to eliminate the necessity for replacing the vibrating dot contact assembly. This allows the device to be easily installed and removed quickly with simple tools. I also came up with a further variation on McElroy's design that can be used on even the "Flat Pendulum" bugs such as the Vibroplex Lightning Bug, Military J-36, Zephyr and Champion models as well as various copies of them and even the Japanese Hi Mound "Coffin" bug.

I currently make "Dot Stabilizers" for the Vibroplex, Speed-X and McElroy keys having the round pendulum and bugs with the flat pendulum, such as the Vibroplex Lightning Bug, Zephyr, Champion and WW2 military J-36 bugs (including the Lionel models) which are based on the Lightning Bug design.

I can also manufacture them for other bugs such as the European made (metric sizes) bugs, etc. as long as you can supply me with the diameter (round) or thickness (flat) of the pendulum and a sharply focused digital photo of the actual bug you want it for. (I only need photos and pendulum dimensions for bugs other than the McElroy and Vibroplex models.) They can be made out of either aluminum or brass though aluminum is the preferred material as it is far less expensive.

I did quit making them for the Japanese "coffin" bugs though as the mechanism is located inside the "coffin" and with the close spacing of the mechanical parts and contacts, it is VERY difficult (sometimes impossible) to mount and adjust a Dot Stabilizer on one of those things. There is too much chance of damaging something so please don't ask me to make one for a "coffin" bug.

I recently acquired a 1913 Horace Martin Vibroplex "Model-X" which is a totally unique bug in that it uses only one contact. The pendulum mechanism is very complex and has a really unique contact arrangement to allow using only the one contact post and vibrating spring for both dots and dashes. When I got it, the dots and dashes were both so scratchy that I was ashamed to put this key one the air so, in keeping with my knowledge of McElroy's Dot Stabilizers and my own re-designed versions, I set out to see if it was even possible to make one for the Model-X. The vibrating arm on it is about 1/4" square and has only one fairly small weight on it.

I machined a 1/4" slot in a piece of 5/16" square bar stock about a half inch long, drilled & tapped two adjacent holes in the top for 4-40 X 1/8" set screws. One anchors the brass block to the pendulum as close as possible to the end of the contact spring and the other locks the "snubber" pin in place, this time on the back side of the spring instead of hooking over it like my normal Dot Stabilizers do. I wasn't sure snubbing it from the back side would work but I needen't have worried. It works quite well and kills the "scratchies" for BOTH dots and dashes. A little bragging here, but I believe I've invented the first Dot Stabilizer to work on the rare Vibroplex Model-X. Actually that's not quite right as it's not only a "Dot Stabilizer", it's actually a "Dot/Dash Stabilizer" as relates to the Model-X.

In the above pictures, the top one shows the Model-X as seen from directly above so you can see the mechanism and see where I mounted the Dot/Dash Stabilizer. The bottom one shows a close up of the stabilizer from a different angle allowing you to see how it mounts to the pendulum and also see the snubber pin protruding through the stabilizer's block and just lightly touching the springy dot contact. This stops the contact from continuing to vibrate as it opens after either a dot or a dash is keyed. Much to my surprise, it worked amazingly well in cleaning up both the dot and dash keying. Gotta love it when a plan comes together, even after all these years (1913 to present).

Right now, I have no plans to actively market the D/DS for the Model-X, but if anyone really wants one, I'll custom make it (brass only) and the cost will be $60 (post paid) to US customers and $70 to international customers (there may be added postage to some countries owing to new USPS rules and price increases just implemented on "First Class International Small Package" mailing.

Install and ordering info for the standard models:

They mount to the arm with a socket head set screw and the proper Allen wrench is included along with a printed set of instructions explaining installation and proper adjustment. Also, they are made entirely by hand so there may be slight differences between each one (this won't affect the operation at all).

The prices are $28.50 post paid for the aluminum and $38.50 for the brass ones to domestic USA customers.

Due to large postage increases and the extra, complicated Customs forms I need to fill out for export, International prices are US$51.50 for the aluminum ones and US $61.50 for the brass ones. This does include international First Class shipping.

Please email me W0EB. before you order to check availability.

If you decide to order one or more, I will need the make/model of the bug(s) you want stabilizers for, whether they are "left" or "right" handed (the bug, not you) and be sure to include your mailing address as well.

I take personal checks, USPS money orders (made out to Aubrey J. Sheldon) and sent to my QRZ listed address or PayPal to w0eb [at] cox dot net .

If you send a check or money order, please be careful to spell my last name right. People keep spelling it SHELTON instead of SHELDON and my bank will NOT cash them!

Incorrect spelling on the check or money order will delay manufacture and shipping of your DS as I have to return it to you for correction and I cannot ship the DS without completed payment.

International customers MUST, repeat MUST use PayPal as it is the only form of payment I can accept from customers in countries outside of the United States.


Some additional images and information provided by a satisfied customer, Fred Schebor, K8NGW after he installed a Dot Stabilizer I made for his left handed Vibroplex Presentation. The following images are Copyright(C) Fred Schebor, K8NGW and are used here by permission.

Left Hand Dot Stabilizer mounted on K8NGW's late model Vibroplex "Gold Base" Original

Since I did not have a photo of a left handed bug with a left handed Dot Stabilizer properly mounted on it to use in the instruction sheet I provide with every dot stabilizer I make, Fred, K8NGW sent me pictures of the one he installed on his Vibroplex Original (Gold Bug) Presentation model. He also gave me permission to use the photo(s) as I needed and gave me a copyright release to do so.

Fred also hooked up a scope and ran before and after tests of the keying waveform using his bug. The first scope screen capture shows the contact bounce that causes the "Scratchy Dots" and the second trace shows the alleviation of the bounce that all but completely eliminates the "Scratchies". Many thanks to Fred for providing these pictures and for his kind permission to use them as I needed.

K8NGW Oscilloscope trace showing a "Scratchy Dot" before installation of the Dot Stabilizer.

And, finally, the last picture shows the effect of an installed Dot Stabilizer on the keyed dot, virtually eliminating the nasty bounce that caused the "Scratchy" dot. I hope these photos and the accompanying explanation helps illustrate the cause and one effective cure for a bug's nemesis, the "Scratchy Dot Syndrome".

K8NGW Oscilloscope trace of a keyed dot after installation and proper adjustment of the Dot Stabilizer.

Jim Sheldon - W0EB

For further information or to order one or more, contact Jim, W0EB.

Page copyright (c) 2019 W0EB, Images copyright (C) 2019 W0EB and K8NGW (used with permission).

Vibroplex, McElroy, Johnson SpeedX, Lightning Bug, Champion, Hi Mound, etc. are trademarks of their respective companies.

Page last updated by W0EB - 02/10/2019 @ 17:00 UTC