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Adjusting Straight Keys, Paddles, & Bugs
A "How-To" Article by N1FN

 
Straight Keys
Paddles
Bencher Paddles
Bugs

These instructions use simple, generally familiar examples of equipment types and are designed to help you find the adjustment that suits you best. What you are looking for ultimately is a particular feel, and that will vary from person to person. Not all keys and paddles offer the same adjustments, or even use the same terminology, but hopefully this will be enough to get you started and to illustrate the general principles.


Straight Keys

The example shown is a Nye Speed-X Model 312, which is typical of a great number of straight keys.    

The available adjustments are:

Arm Tension, the force needed to move the lever up and down. It's usually exerted by a coil spring between the arm and the base, and is adjusted at B in the drawing.

Bearing Tension, the setting of the pivot bearings on which the arm rotates. It is controlled by the pressure on the bearing surfaces, and there is one bearing (and one adjustment) on each side of the pivot arm, shown at A1 and A2 in the drawing.

Contact Spacing, the space between the two electrical contacts when the key arm is not depressed (unkeyed). The contacts are located beneath the arm, toward the front of the key. The adjustment for the 312 and similar keys is at the back end of the arm, shown as C in the drawing.

The two unmarked screws at the back of the key, on either side of C, are the binding posts for connecting the key to the transmitter.

Here are the four steps you will need to "set up" your key:

1. UN-adjust the key. That's right- we need to loosen everything up and get to a common starting point, because each of the adjustments has some impact on the others. Loosen the spring tension on the arm (B) until no resistance is felt when you depress the knob. Open the contact spacing (C) as far as you can without removing the adjustment screw from the arm. Loosen the bearing tension screws (A) until the arm wobbles loosely.

2. Adjust the bearing tension. Choose one of the two bearings and tighten its adjustment screw (A) until you can just barely feel a bit of friction as you move the arm up and down. Now back the screw off until just the point at which the arm moves freely again- usually it's just a fraction of a degree of screw rotation, or about as fine an adjustment as you can make. Repeat with the other bearing tension adjustment screw. Setting the second bearing is likely to have had some effect on the first, so readjust the first bearing and then finally the second bearing. At this point the arm should move up and down perfectly freely, with no sideways play or "slop."

3. Adjust the contact spacing. The contact spacing determines the amount of vertical movement when you depress the arm. It's entirely a matter of taste, but if you haven't used a key before and haven't developed your own preferences, start with a sixteenth of an inch or about the thickness of a penny. Adjust screw (C) until you have the desired spacing between the contacts.

4. Adjust the arm tension. Tighten the arm tension adjustment screw (B) to a comfortable level of tension on the arm. Again, this is a matter of preference, but it is possible to suggest a good rule of thumb if you haven't developed preferences- set it for the minimum amount of tension that will allow you to feel that you are in control of the key.


Paddles

A dual paddle is a little more complex than a straight key, but it can be thought of as two straight keys side by side and operating horizontally rather than vertically. There are also single paddles, but there is very little difference in the way they are adjusted.

The example shown is a Hi-Mound Model MK-706, which is typical of a great number of dual paddles.  The available adjustments are:

Lever Tension, the force needed to move either of the two levers from side to side. It's usually exerted by a coil spring between the paddle lever and the adjusting screw, and is adjusted at B in the drawing.  Some paddles will have separate adjustments for each lever.  Note that paddles like the "Bencher" have the tension controlled by a single long spring running around a post at the back of the unit. The two screws to which the spring is attached control the tension by changing the angle at which the spring pulls.

Bearing Tension, the setting of the pivot bearings on which the paddles rotate. It is controlled by the pressure on the bearing surfaces. In the paddle shown, there is a single adjustment at the center of the bearing frame, shown at A in the drawing. Some paddles will have separate adjustments for the two arm pivot bearings, and some paddles will even have separate adjustments for the upper and lower bearing surfaces.

Contact Spacing, the space between the two pairs of electrical contacts when the levers are at rest (unkeyed). The contacts on the 706 are located at the rear end of the lever. The adjustments for the two arms are shown as C in the drawing.

Here are the steps you will need to "set up" your paddle

1. Un-adjust the paddle. That's right- we need to loosen everything up and get to a common starting point, because each of the adjustments has some impact on the others. Loosen the spring tension on the paddle levers (B) until no resistance is felt when move the levers. Open the contact spacing on each side (C) as far as you can without removing the adjustment screw from the arm. Loosen the bearing tension screw (A) until the arms wobble loosely.

2. Adjust the bearing tension. Tighten the bearing tension adjustment screw (A) until you can just barely feel a bit of friction as you move the levers back and forth. Now back the screw off until just the point at which the arms move freely again- usually it's just a fraction of a degree of screw rotation, or about as fine an adjustment as you can make. If the arms have separate bearing adjustments, perform this adjustment for each arm individually. At this point the two levers should move from side to side freely, with no vertical play or "slop"

3. Adjust the contact spacing. The contact spacing determines the amount of horizontal movement when you depress the arm. It's entirely a matter of taste, but if you haven't used a paddle before and haven't developed your own preferences, start with about the thickness of a a dime or a bit less. Adjust screws (C) until you have the desired spacing between the contacts on each side. The spacing does not have to be identical, and in fact many "bug" operators prefer a greater gap on the dash paddle.

4. Adjust the arm tension. Tighten the arm tension adjustment screws (B) to a comfortable level of tension on the arm. Again, this is a matter of preference, but the general rule is to set it for the minimum amount of tension that will allow you to feel that you are in control of the paddle. There is no reason the tension should be the same if you don't want it that way. For example, if you have never used a paddle before you may find it easier to learn if tension is set slightly greater on one side or the other.


Bencher Paddles


Bencher BY-1 Paddle
Links for larger, labelled images will be found below.

The popular Bencher line of paddles poses some interesting problems in adjustment, because the design is so different from more traditional straight-lever paddles.  The Bencher uses a “cantilever” arm design, so that the contacts are at the front of the paddle and the movement of the contacts is essentially from back to front rather than from side to side.  This design, coupled
with the distinctive shape of the finger-pieces, is why the term “Iambic” is so often associated with the design of the paddle.  But in fact, the Bencher  is a simply a variation on the theme of dual paddles, and Iambic refers only to the keyer with which the paddle is used. Click here for a discussion of iambic paddles and keyers.

Adjustment of a Bencher or other cantilever style paddle  is not as difficult as it looks. While the appearance is technically daunting, the Bencher is actually quite robust, and capable of adjustment in the usual ways to suit any operating style.
 

Naming of Parts

The parts of the Bencher need to be understood before an attempt is made to adjust the paddle.
Critical parts or adjustment screws are indicated in the illustrations.

The two paddle arms are the S shaped pieces of metal which have the plastic finger-piece at the
front and a contact at the other end, adjacent to the two contact posts. The paddle arm is attached
to the semi-circular pivot plates with a single screw which goes through the arm, and extends
beyond the pivot plate to rest against the stop screw.

The pivot plate rocks back and forth as the paddle is used, and adjustment consists of
locating the pivot plate properly and controlling the extent of its movement.  As stated, the paddle
arm is attached to the front of the pivot plate with a screw that goes through the plate and
controls the resting position of the plate when it is under tension from the spring.  The spring
attaches to a long screw that goes through the pivot plate from the upper quadrant. There is a
flat spot in the threading of the screw (on the inner side of the pivot plate), where the end of the
spring is attached.  As the screw is moved in or out, the amount of tension is changed as the angle
between the spring and the pivot plate changes.   The plate moves against two needle bearings
(upper and lower on each side)  with the needle bearings themselves extending forward from the
bearing block and the nylon bearing seat fixed in the back side of the pivot plate.

There is also a “locator” screw which goes through a large, unthreaded hole in the pivot plate and
screws into the bearing block.  The locator screw  is not actually attached to the pivot plate.  The
head of this screw limits the distance that the plate can move outwards if the paddle arm is moved
the “wrong way.”  In normal use it serves no purpose, but when the arms are moved backwards
(e.g. to clean the contacts) it does serve to keep the pivot plate from coming off the bearings.
 

The available adjustments are:

Paddle Arm Tension, the force needed to move either of the two levers from side to side. It's
exerted by a long coil spring which attaches to one adjustment screw, goes to the back of the
paddle and around a post, and then back up to the other adjustment screw. The two screws to
which the spring is attached control the tension by changing the angle at which the spring pulls
against the pivot plate.
.
Bearing Tension,  adjustable only as a side-effect of  varying the spring tension on the pivot
plate.  With needle bearings and nylon seats, it is essentially ignorable.

Contact Spacing, the space between the two pairs of electrical contacts when the levers are at
rest (unkeyed). The contacts on the Bencher are an adjustable contact on the end of a screw going
through the contact post, and a fixed contact on the end of the paddle arm. The contact spacing
determines the distance the paddle arm will move when keyed.

Pivot Plate Position, the location of the pivot plate.  There is really only one adjustment, namely
the resting position (paddle unkeyed) controlled by the stop screw.  The locator screw limits
outward movement of the pivot plate when the paddle arm is moved “backwards.”

Here are the steps you will need to "set up" your Bencher paddle

1.  Open up the contacts.  Loosen the transverse locking screw (the smaller, upper one) on each
contact post and then back out the contact screw until the contact itself is up against the inner
surface of the post.

2.  Inspect and adjust  the position of the pivot plates.  They should be perfectly parallel with
the front surface of the bearing block.  Looking from the side of the paddle, you should see that
the tops of the pivot plates form a straight line, parallel with the bearing block.  If they don’t,
adjust the stop screws (accessible from the back of the bearing block) until the plates line up.
When the above adjustment has been made, check the locator screw to see that the head is
approximately 1/8" out from the front of the pivot plate.

3. Adjust the contact spacing. The contact spacing determines the amount of horizontal
movement when you move the finger-piece or “key” the paddle. It's entirely a matter of taste, but
if you haven't used a paddle before and haven't developed your own preferences, start with about
the thickness of a dime or a bit less. Adjust the contact screws until you have the desired spacing
between the contacts on each side, then tighten the locking screws above the contact adjustment
screws.  The spacing does not have to be identical, and in fact many former "bug" operators
prefer a greater gap on the dash paddle.
 

4. Inspect contact alignment.  When keyed, the contacts should meet flush and not at an angle.
If they do not meet flush, you can usually fix the problem by loosening the nut that holds the
contact post (on the base of the paddle) and rotating the post slightly.  If you cannot achieve a
flush meeting of the contacts after performing ALL of the preceding adjustments, then it is
probably that the paddle arm has been bent.  If you find it necessary to straighten the paddle arm,
remove it  from the pivot plate and hold it firmly with a pair of pliers (or in a vice) and bend as
necessary.  You can also bend other (front) end of the paddle arm if you want to make a slight
adjustment in how close together the finger-pieces are.

5. Adjust the arm tension. Adjust the  tension adjustment screws to a comfortable level of
tension on the arm. Again, this is a matter of preference, but the general rule is to set it for the
minimum amount of tension that will allow you to feel that you are in control of the paddle. There
is no reason the tension should be the same if you don't want it that way. For example, if you have
never used a paddle before you may find it easier to learn if tension is set slightly greater on one
side or the other.  It will be pretty obvious, but tension is increased by turning the adjustment
screw out (counterclockwise), and decreased by turning it in (clockwise).

Bencher Paddle Illustrations:
 

Bugs


Hi-Mound BK-100. Click the image to view in full size.

"Bug" is a term used to describe an automatic or semi-automatic Morse key,  that is, a mechanical device which will automatically generate a series of dots and/or dashes.  The most common varieties, like the Hi-Mound BK-100 shown above and the most familiar of the many GHD and Vibroplex models, are semi-automatic.  This means the dots are formed automatically, while the dashes are formed manually. There have been many bugs with fully automatic dashes as well as dots, and the author owns an early THREE-paddle bug which had automatic dots and dashes, and a separate manual dash paddle for "long dashes" used in landline telegraphy.

Virtually all of the bugs which you are likely to encounter work the same way.  When the lever is moved to one side, a pendulum is allowed to swing back and forth, making repeated closure of a pair of contacts to generate dots. The oscillation (and generation of dots) stops when the lever is released. The speed of the osciallation is controlled by the position of the weight on the pendulum arm.  The closer the weight is to the pivot, the faster the pendulum will move.

When the lever is moved to the other side, it closes the dash contacts, acting very much like a straight key turned on its side.

Naming of Parts

Over the years the critical parts of a bug have had a lot of names, but I've tried to use the most commonly understood ones as shown in the diagram.  You won't find exactly the same parts on every instrument, but usually you can figure out what does what if you understand the basics.  And at this point I'd like to thank Bill, W1HIJ, for kindly providing a lot of background information for this article, along with some judicious quotes from an Army Tech Manual (TM11-459, 1945).  I'll be paraphrasing those instructions, along with a simple method for testing adjustment using a VOM which Bill also described.  In describing the parts there are a couple places where I'll show the name used in the Army Tech Manual in parentheses.

The Lever.  The lever on a bug is usually split, that is, what appears to be a single control at the front of the bug actually drives two separate levers at the back of the device.  The dash part of the lever is short and simple, while the dot part is more complex, being  attached to the pendulum.

Bearing Tension Adjustment Screw.  The lever his held in place on a pivot bearing, and there is usually a screw to adjust the tension so that the lever swings freely in both directions, without any sloppiness.

Arm Tension Adjustment Screws.  These adjust the tension of springs which press against the lever to return it to the center or resting position.

Dash contacts.  The adjustment screw adjusts the spacing between the contacts, which determines how far the lever must move when making dashes.

Dot Contacts.  The screw adjusts the spacing between the contacts, which is quite different from the spacing on the dash contacts.  The spacing here, in conjunction with the dwell screw, determines the "shaping" or weight of  the dots.

Dot Stop Screw (back stop screw).  This screw adjusts the resting position of the lever, so that oscillation is stopped by the damper.

Damper (deadener).  The damper is a flexible device for instantaneously absorbing the momentum of the pendulum so as to stop (damp) the oscillation.  In the case of the BK-100 (illustrated) it is a loose metal sleeve on a shaft.  Other bugs use rubber "bumpers."

Pendulum (reed).  The pendulum consists of an arm along which a weight can be moved.  The position of the weight determines the "moment" of the pendulum, or the speed at which is oscillates.

Dwell Adjustment Screw (front stop screw).  This screw adjusts the width of the pendulum's arc, and to the extent that the pendulum moves farther than is necessary for an instantaneous meeting of the dot contacts, the contacts stay closed (or dwell) until the pendulum swings back.

Procedure For Adjusting the Bug
 

1.  Back out the two lever tension adjustment screws so that the lever moves freely to left and right.

2.  Check and adjust the pivot bearing tension.  The lever should move freely left and right, with no up and down sloppiness.  If it requires adjustment, loosen the locknut and the screw until the lever feels sloppy.  Tighten the bearing screw until the slightest amount of friction is felt as you move the arm, then back the bearing screw off until the friction just disappears.  Tighten the lock nut.

3.  Adjust the dash contacts as desired for comfortable movement of the dash lever. If you aren't used to a bug and don't know exactly what you are looking for, start with about 1/16 of an inch.  Adjust the dash tension screw to a comfortable level of tension.

4.  Adjust the resting position of the pendulum.  Do this by adjusting the dot stop screw until the end of the pendulum just lightly makes contact with the damper.

5.  Adjust the pendulum weight to a position appropriate for the speed you want to set the bug up for.  If you have not used a bug before you will probably want to set the weight near the end of the pendulum arm, for relatively slow speed.

6.  Adjust the dwell screw so that there is a small gap between the end of the screw and the side of the arm when you swing the lever to the dot side and hold it.  This gap will vary significantly depending on the position of the screw along the length of the arm or pendulum. On the BK-100 it will be about 3/16", but the Army Tech Manual (for use with a particular Vibroplex) specifies .015"

7.  Swing the lever over to the dot side and stop the oscillation with a fingertip, but still holding the paddle over.  Adjust the dot contact screw so that the contacts just meet.

8.  Adjust the dot lever tension to suit.

At this point, normal activation of the dot lever should result in a string of 20 or more dots being generated before oscillation slows down.  If not, try some different adjustments of the dwell screw (and then readjust the dot contacts)-- you should be able to see easily whether a wider or narrower gap on the dwell screw is necessary, and find an appropriate adjustment. Most bugs can be adjusted to provide 20 or more dots from a single closure, but if yours can't, don't worry about it-- just set it for the most you can get out of it.

Note that when you change the bug's speed by moving the pendulum weight, you may need to repeat steps six and seven, particularly if you are changing speed by more than a few wpm.

Verifying Proper Dot Formation.

As mentioned above, Bill W1HIJ describes a simple way to use a VOM to determine that your dots are being generated correctly.  Keeping in mind that in a string of dots, the signal should be on and off for exactly the same amount of time (space between dots equals length of dot), just hook up an analog VOM (set for resistance) to the bug's output connections.  Key the bug, and you should observe the meter vibrating at about the mid point of the range.  While observing the meter, fine-tune the dot contact spacing  until the needle hovers  at midrange, indicating a "50% dwell" or perfect weighting.
 
 

Finally, the last word from the Army Technical Manual:
"The bug is designed to make sending easy rather than fast, and perfect control of the key is far more important than speed.  Be especially careful to send dits accurately.  Not all radio operators have equally sensitivie hearing, and careless sending on the semautomatic key will not be understood."

On Iambic Paddles and Keyers

To begin at the beginning, there is no such thing as an iambic paddle!  The confusion came about in large part because the Bencher “Iambic Keyer Paddle,” as it was labeled in magazine ads,  was introduced shortly after the iambic keyer itself was developed, and similar names have been used by other paddle manufacturers.  Many people tend to read “Iambic Keyer” as a description of the paddle rather than the device for which it was designed to be used, the "iambic" electronic keyer.  The proper terminology is "dual paddle" as opposed to "single lever paddle." 

Early electrical and electronic keyers were an emulation of mechanical keying devices such as bugs, where you would press a lever in one direction to get a series of dots, and the other direction to get a series of dashes (or make them manually in the case of a semi-automatic key, or bug).  The first keying devices, or paddles, had a single lever and were known variously as sideswipers, slap-keys, and paddles.  All electronic keyers work this way, but a more recent development (mid 1950's) is the iambic or "squeeze keyer" which adds a level of functionality to the basic "dit OR dah" scenario.

With an iambic keyer, you get an alternating series of dots and dashes when both levers are activated at same time, or squeezed.

The term "Iambic" comes from poetry, where it is used to describe a rhythm consisting of alternating unstressed and stressed syllables, as for example "Come live with me and be my love!" When you say that out loud you will easily hear the  "di-dah-di-dah-di-dah-di-dah" rhythm,  or in other words the rhythm you get when you "squeeze" the paddles connected to an iambic keyer.  The series can start with either a dit or a dah, depending on which lever makes contact first.  If the electronics in the keyer cannot determine which contact hit first (logically simultaneous), it will default to starting with either a dit or a dah and then begin alternating.  Just for the sake of being complete here, if you squeeze the paddles so as to get "dah-di-dah-di-dah-dit" the rhythm is technically "trochaic" rather than "iambic,"  but that's trivia you probably don't need to know.

Dual paddles like the Bencher can be used with “non-iambic” keyers, and single lever paddles can be used with iambic keyers (although the true iambic or squeeze-key features of course are unavailable with a single lever paddle). 
 

 

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