Weekend Radio
Projects you can build - By: Mike Maynard, K4ICY

The Depot Cootie Key - An Easy-to-Build Single-Lever Morse Paddle

As Presented in The Printed Circuit, Newsletter of the Tallahassee Amateur Radio Society (TARS). January 2015 - Page 13  Click Here for an index of Electronics Projects

 

Build Your Own “Depot Cootie” Key for as Little as $10!


       As the great homebrewing advocate Frank Harris, KOIYE, once put it: "Be The Complete Ham," no one can rightly call themselves a "real" ham until they’ve attempted to build some piece of their own equipment. The very act of homebrewing some station accessory or piece of radio gear divides the sheep from the goats - or the Amateur from the appliance user.  Sure, not all hams are so technically inclined, but this is a teaching hobby and if the hams of the early part of last century could be compelled to understand the inner workings of their radios and craft just to be granted a class A or B license, then the hams of today can certainly endeavor to go that one extra step.

        The "Cootie" or side-swiper key, as mentioned in my associated article was one of first easy-to-build "alternative" key solutions for the telegraph operator of the late 19th century and later for the experimenting ham of the radio age.  The side-to-side motion was easier on the wrist and an operator could actually send faster with less work.  The literal backbone of this simple key relies on a springy piece of steel to act as the actuator arm, pivot bearings and retracting springs all in one.  All one had to do was affix the other end of the arm and provide some adjustable contacts that would be  available  on  both  the

Depot Cootie Key 

left and right.  Many a new ham of not-so-prosperous times found the "Cootie" to be an economic necessity for enjoying their new Novice licenses.  As the early part of the 20th century rolled on, hams found themselves converting surplus or broken semi-automatic "Bug" keys to single-lever paddles.  Later on, with the advent of the transistor age, when electronic keying became an affordable reality, a few enterprising key manufacturers produced dedicated solid arm models which promised incredible speeds and improved sending accuracy.  A few particular models are still in production today and are considered popular and the key of choice for speed aficionados.

       "Can I build one for myself so easily?" you say.  Yes, and I'll show you an example that took me only half an hour to build and it works great!  There's a beauty in constructing something with simple parts.  First of all, we need to do a little "up-cycling" by re-using an old part that would have normally gone to the landfill.  Go take a look at your hacksaw, in particular, the type used for cutting light metal or wood and has a thin blade that is at least a foot long and ½” wide - which is the part we’ll need.  If you don't have one lying around, that's okay, a pack of replacement blades are not that expensive.  You'll need to do a little prep to the blade once you have your other parts, so keep these old and worn blades handy for future “gift” keys.

Hack Saw and Corner Braces
       Now I can't endorse one hardware store over another here, but I'm sure that you'll find everything you’ll need at your local Lowe's®, Ace Hardware®, or Home Depot® stores, so there'll be no need to order anything, and the tools will be minimal.  For my build, I went to The Home Depot® [Yes, I named this key the "Depot Cootie,"  but if anyone asks, maybe I was re-envisioning the days of railroading telegraphy past.]  Anyways, you can expect to find all the parts on the list to cost you at least $10 and not much more.  If you have a piece of wood lying around that you can cut to form the base of the key, then you're already ahead, but I happened to find this piece of pre-fab molding in the trim section for only 84 cents - and it already had an attractive chamfer on it!

        Aside from the used ½”-wide hacksaw blade and a good wooden base, the right angle brackets are the key to this assembly.  I used 1-½”  corner braces I got in a pack of four for only a few bucks.  Once affixed to the base, the bottom holes on the vertical  section  are used to mount the blade and the  contacts  while  the 

top holes serve to connect the wires.  You'll see that the list of fasteners is a little extensive including two kinds of lock washers and pan-head machine screws, but nothing here is critical and I leave it up to you to figure out a solution that works best for you.  The one part that may be important is to use all #8 faster sizes as well discuss later.  Also, everything should be stainless steel if you can get it so that your key will not suffer from poor electrical connections later on due to surface oxidation.

Hardware

HARDWARE:  Steel ½” Hacksaw Blade, Pre-Cut 4-½” x 2-¾“ x 1”  (not critical) Fiberboard Trim Block, (4) 1-½” (½“ wide) Galvanized Corner Braces (Brass may contain a non-conductive coating), (3) #8-32 x 5/8” Pan (or round) Head Machine Screws, (2) #8-32 x 1” Pan (or round) Head Machine Screws, (6) #8-32 Machine Screw Nuts, (6) #8 Ext. Tooth (Star) Lock Washers, (6) #8 Flat Washers, (6) #8 Med. Split Lock Washers, (2) #8-32 Wing Nuts, (4) Small Adhesive-Back Rubber Feet, Finger Piece taken from a Chip-Clip – or use anything that can be glued on.

TOOLS:  Large Tin Snips (Metal Shears), Drill (for pilot holes in wood), Screwdrivers, Socket Drivers, Metal File, (opt.) J.B. Weld

Cut the blade with Metal Shears

INSTRUCTIONS:

1)     Prepare the hacksaw blade.  My goal for this project was to eliminate as much of the metal-working danger as possible.  I do not recommend drilling or cutting into the hardened spring steel that the blade is made from unless you have access to a drill-press or metal-cutting tools.  We have an advantage!  There happens to be a hole near each end of the hacksaw blade from which it's affixed to the hacksaw handle.  The hole happens to fit a #8 screw (typically,) if not, a little drilling with a metal bit to bore a larger hole may be needed.  Now we actually need to cut off a length of the existing blade to use for our key.  For this you should use a good pair of tin snips (metal cutting shears) to cut a piece of the blade which will include the hole on the opposite end from the cut.  3-1/2" to 4-1/2" will be plenty - or suit to your own design.  Important: Be sure to wear safety goggles and gloves when cutting the blade as the hardened steel is brittle and may produce flying shards.  If you don't have a pair of tin snips, then you could try holding the blade in a bench vice, and with a pair of vice-pliers, bend the blade near the cut line until the metal work-hardens and snaps apart.  Here, you should file down the sharp corners and teeth if you wish.  Also file or sand off the paint where the end with the hole is and also where the contacts will land to promote a clean electrical connection.

2)     Prepare the arm pivot assembly.  Sandwich the blade and the backs of two corner braces together, aligning the holes of the braces with that of the blade-end.  Attach fasteners as shown in the diagram.  The blade adds a small amount of clearance between the braces so build this part first before affixing to the base.  The blade should be perpendicular to the sides of the braces and eventually parallel to the surface of the base.  Once  you  tighten  the  fasteners

you should really have no issues with the blade moving from its placement angle, but if it does then you could bind it to (only) one of the braces with J.B. Weld® epoxy.  A blade without a pre-drilled hole can be effectively held between the two screws along the vertical section of the brace assembly, but you may have to address the contacts’ landing position if the blade doesn’t line up.

 ...building process

3)     Prepare the base.  There are no critical measurements to give you, but start off by dividing the center of your wooden base with a pencil line.  Place the pivot assembly near the back and align the blade to center along the pencil line.  Pencil in the inside of the brace's screw holes to mark where to pilot-drill for the wood screws that are often provided with corner braces.  The distance from the pivot to the contacts is not critical, so gauge where you would like the contact posts to sit, and for placement, sit the remaining corner braces in their positions with the backs (upward side) facing towards the center, space them out each from about ½" to ¾" of distance from the center line.  Mark the pilot-holes on the base through the screw holes in the braces.  Don’t assemble the contact hardware just yet until the pivot/arm assembly is in place.

4)     Using the supplied wood screws attach the pivot assembly to its position, and then attach the braces for the contacts.

5)     Assemble the contact hardware.  The goal here is to have adjustable contact spacing that is also precise.  The stainless steel screws are perfect for good conductivity, but use your imagination on the arrangement.  In my example, I used a wing nut to serve as a hand-tightening lock nut to allow for easier adjustments on-the-fly.  However, it  is  not  perfect.   

 For  a  better method, I suggest using a nylon-insert lock nut permanently attached to the corner brace using J.B. Weld® epoxy resin. You can also "Weld" the wing nut to the pan-head end of the machine screw which will give you a precise adjustment mechanism - just make sure there is good electrical conductivity along some part of the screw.  You can also “Weld” the contact-side nut to the brace and leave the wing nut free to act as a stop nut.  Like I said: nothing critical here - just use your imagination.

Explded View of Depot Cootie

6)     Attach a finger piece.  I found these ready-made finger pieces loosely attached to some "Chip Clips" we had lying around.  The clips are easily broken, but the finger pieces were made of some kind of nylon and had a recess that was the same size as the blade!  Of course, you can make this part out of anything to add your personal touch; use anything from guitar picks and wooden nickels to layers of heat-shrink tubing or electrical tape.  A dull hacksaw black is not too dangerous if covered with something.  Your body should be electrically insulated from the key anyways to protect from high voltages or dangerous RF.

7)     Attach some small adhesive-back rubber feet to the bottom of the base.  This key will be too light by itself to operate without sliding around on the table, so rubber feet will help.  Using a sheet of soft high-friction silicone adhered to the entire bottom surface of the base will be better.  You can also attach it to a larger piece of wood or to the table itself!

8)     Attach the key's wires either by wrapping the wire around the screws and then clamped down in between two washers held in place by a nut or solder terminal lugs on to the wire and clamp the lugs to the top positions on the corner braces as shown.

      Adjustment should be straight forward - the gap between the end of each contact screw and the blade surface should be set for best comfort.  The Cootie key can not only be used for side-swipe sending but to command an "iambic" automatic keyer.  If you are using a keyer then you may want extremely tight spacing.  As you can see in my example, I added a second blade from the top screw position, angled down to the finger piece.  I did this to effectively double the "spring" tension because I needed more resistance in moving the arm a very minute distance at only 0.005", the thickness of a sheet of paper.  Single-lever control of an automatic keyer is not the same in operation as with a dual-lever paddle where "squeezing" achieves the desired result of an automatic "iambic" pattern of alternating 'dits' and 'dahs'.  You have to manually alternate between each 'dit' and 'dah' contact to achieve this pattern and your timing has to be close enough so that you don't end up getting unintended elements. There are some advantages though as it's claimed that using a single-lever key to operate a keyer produced fewer errors in sending.  Many find the single-lever key easier to learn which is why it is perhaps a "best seller" by a certain key manufacturer over their other products.

Views

       Now to talk a bit about using the Cootie key in its intended fashion: which is to send code by the “side-swiping” method.  For one of many instructional YouTube videos visit this link: https://www.youtube.com/watch?v=ZfLrgYHIpjo (An introduction to the Sideswiper)  In sides-swiping 'dits' and 'dahs' are produced manually as with a straight key, but in succession of moving the arm from one contact to the other.  As by common practice, elements are always started by moving the paddle from right to left – where the left contact is always made first - then alternately keying between each opposing contact until the character is completed.  The left contact is always keyed first regardless of character.  This method of sending is claimed to be "the hardest" to learn of all keys, but once the user has become more practiced at it, side-swiping becomes one of the most comfortable!

       The adjustment of a Cootie key (or single-lever paddle) used in side-swiping differs from that of electronic keying.  The "weighting" of the side-swiped elements tends to be “heavier,” which to those that don't know, weighting is the term used to express the timing ratio between the marks (on) and spaces (off) of a character element.  A repeated keyer ‘dit’ is generally set to a 1:1 ratio and you should get a "dit dit dit" sound, but in sideswiping, you're more likely to get a "diidiidit" sound which is one reason why side-swiping has such a characteristic sound on the air.  To alleviate the propensity for heavy weighting, it is generally better to set the contacts very wide apart so that your wrist has to take more time to move the key arm from one contact to the other - maybe up to a ¼" gap.  Don't fear side-swiping, just give it a good College try for yourself.

       If you've built your own Cootie key then congratulations and welcome to the club!  Homebrewing hams are a commodity compared to days of old, not to mention CW operators for that matter.  And if you're a side-swiper (like myself) then truly you are a rare find.

73! DE Mike, K4ICY k4icy@arrl.net

Edited: 02/19/15
©2012-2016 Copyright - Michael A. Maynard