How to adjust a straight key: spring tension and contact gap
Most straight keys have two adjustments that matter: the contact gap, which sets how far the knob travels before the contacts close, and the spring tension, which sets how hard you have to press and how briskly the lever comes back up. A common order is the gap first and the tension second; turn each screw only a fraction at a time, and tighten the locknut when you are done. The right setting is the one that lets you send evenly with a relaxed hand, so the last step is always to send and listen.
Find the two screws
Straight keys come in many designs, but nearly all share the same parts. A lever pivots on a bearing. The knob sits at its front end. Two contacts, one on the lever and one on the base, close when you press the knob down. A spring pushes the lever back up when you let go.
The two adjustments are usually screws, each with a locknut to hold it once it is set:
- The gap screw limits how far the lever can travel, and so how far apart the contacts sit at rest.
- The tension screw sets how hard the return spring pushes the lever back up. More tension makes the key stiffer.
Where they sit varies from key to key. If yours are not obvious, find them by experiment: loosen a locknut, turn its screw a quarter turn, press the knob a few times and notice what changed. If the knob now travels further or less far before the contacts meet, that was the gap. If it now feels firmer or softer, that was the tension. Turn it back afterward, so you start from where you were.
Some keys also have adjustable screws at the pivot, one on each side of the lever. If yours does, leave them alone unless the lever wobbles from side to side or sticks. They should be just snug enough that the lever moves freely up and down with no sideways play.
The contact gap: what it changes
The gap is the distance between the contacts when the key is at rest, and it sets how far the knob moves before anything happens.
A wider gap gives a longer stroke. The key feels deliberate, and a hand resting on the knob is less likely to close it by accident. But the contacts close later in each press and open earlier as you release, so your dits and dahs come out a little shorter than your hand movement, and at speed the long stroke becomes hard work.
A narrower gap gives a short, quick stroke that suits higher speeds. The contacts close early and open late, so elements come out a little longer. Too narrow, and a slight tremor or the weight of a resting finger closes the circuit, and you send dits you never meant to.
One common starting point is a gap you can see clearly when you look at the contacts from the side, with the knob making a short, definite movement before they meet. Some beginners like it a little wider, for the feel of the stroke, and many operators narrow it as their speed rises.
The spring tension: what it changes
More tension makes the key firmer. The lever snaps back the instant you relax, which gives crisp, slightly lighter elements. Too much, and every dit is a push, your forearm tires, and short elements start to clip.
Less tension makes the key softer and easier to press, but the lever comes back up more slowly, so elements run a little long. Too little, and the weight of your fingers resting on the knob is enough to hold the contacts closed, and the key feels mushy.
A common starting point is the lightest tension at which the weight of your relaxed fingers on the knob does not close the contacts, and the lever rises briskly the moment you let go. From there, firm it up a little at a time if your dits feel sloppy.
Reading the symptoms
Gap and tension both change how long the contacts stay closed compared with how long your hand presses, which has much the same effect on the sound as the weighting setting on a keyer. Dit to dah ratio and weighting in Morse code explains why that ratio matters. In practice, you adjust by symptom:
| If you notice | Likely cause | Try |
|---|---|---|
| Stray dits, contacts closing on their own | Gap too narrow, or spring too soft | Widen the gap a little, or add tension |
| Clipped, choppy dits and dahs | Gap too wide, or spring too stiff | Narrow the gap, or ease the tension |
| Heavy dits that run long | Spring too soft, or gap too narrow | Add a little tension, or widen the gap a little |
| An arm that tires quickly | Spring too stiff, or a long stroke at speed | Ease the tension, then narrow the gap |
| A key that feels mushy | Spring too soft | Add tension |
Setting it up, step by step
- Sit as you send. Put the key where it will live, at your normal height and distance, before you adjust anything. A key set up at an odd angle feels different once it is in its real place.
- Loosen the locknuts on the gap and tension screws.
- Set the gap. Close it until the contacts nearly touch, then open it in small steps until the knob makes a short, definite movement before the contacts meet.
- Set the tension. Back it off until your resting fingers close the contacts, then tighten in small steps until they no longer do and the lever lifts briskly.
- Send a test. Send runs of dits (H,
...., and 5,.....), runs of dahs (O,---, and 0,-----), and a sentence of plain text. Record it if you can, and listen. - Change one screw at a time, a fraction of a turn, then send the same test again. Changing both at once leaves you guessing which one helped.
- Lock it. Hold the screw still while you tighten its locknut, so the setting does not shift as the nut bites.
- Live with it. Give a setting a few sessions before you change it again. Your hand adapts, and what felt odd at first often feels right a few days later.
While you are there, look at the contacts. If the key starts missing elements, a common fix is to close the contacts lightly on a strip of clean, plain paper and draw it through a few times. Avoid files and abrasive paper, which wear the contact faces away.
Stop the key from walking
A straight key that creeps across the desk as you send makes you chase it, which spoils your timing and tires your arm. Ways to anchor it:
- Weight. A heavy base helps most. If yours is light, screw it to a heavier board or a metal plate.
- Grip underneath. Rubber feet, or a sheet of non-slip mat under the base, stop most sliding.
- Fix it down. A clamp to the edge of the desk, or strong double-sided mounting tape under a board, holds a key that nothing else will.
- Press straight down. A key that walks away from you is often being pushed forward. Line it up with your forearm and press down, not out. How to use a straight key without tiring your arm covers the grip and posture that help.
Keys on a Mac
A real key feeding a Mac is adjusted exactly as above. Many USB Morse keys and keyers work by typing a keyboard key, and Dot & Dash can use that key as its straight key once you choose it in Settings. A plain Mac keyboard has nothing to adjust, so there the app does the adapting instead, learning the length of your dit as you key. Connecting a USB Morse key or keyer to a Mac has the details.
Questions
Should I adjust the gap or the tension first?
A common order is the gap first, because it sets how far the lever travels, then the tension, which sets how firmly it travels that distance. After that, fine-tune them one at a time.
Why does my straight key send dits by itself?
The gap is probably too narrow or the spring too soft, so a slight movement or the weight of your fingers closes the contacts. Widen the gap a little, or add tension.
How often should I readjust my key?
Only when something feels or sounds wrong, after you move the key, or as your speed changes. Check the locknuts now and then, because a screw that has crept is a common reason a key suddenly feels different.
Does a closer gap make me send faster?
It shortens the stroke, which makes higher speeds easier to reach, but it does not set your speed. Your speed still comes from your hand, and a gap too close for your current skill adds stray dits.