Iambic keying explained: mode A vs mode B
Iambic keying means squeezing both levers of a dual-lever paddle so the keyer sends alternating dits and dahs, starting with the lever you closed first. Mode A and mode B differ at one moment only: when you let go of the squeeze. In mode A the keyer finishes the element it is sending and stops. In mode B it finishes that element and then sends one more, the opposite one.
Everything else is the same in both modes: the speed, the spacing inside a character, what happens when you hold just one lever. If you never squeeze, you will never hear a difference.
What a squeeze does
A paddle on its own is two switches. The keyer behind it does the timing. Hold the dit lever and it sends dits, one after another, each one unit long with one unit of silence after it. Hold the dah lever and you get dahs, three units each. Let go and the keyer stops at the end of the element it is sending, so every dit and dah comes out full length. If that chain is new to you, What is a Morse keyer, and do you need one? starts from the beginning.
Press both levers together and the keyer alternates. Close the dit lever first and it sends .-.-.- and on for as long as you hold; close the dah lever first and it sends -.-.-. and on. The name is usually traced to poetry, where an iamb pairs a short beat with a long one, much like a dit and a dah.
That alternation is why squeezing saves work. A good number of characters are runs of alternating elements:
| Character | Code | Squeeze with |
|---|---|---|
| A | .- |
dit lever first |
| N | -. |
dah lever first |
| R | .-. |
dit lever first |
| K | -.- |
dah lever first |
| C | -.-. |
dah lever first |
| Period | .-.-.- |
dit lever first |
| AR | .-.-. |
dit lever first |
Without a squeeze, C is four separate movements: dah side, dit side, dah side, dit side. With a squeeze it is one: close the dah lever, add the dit lever, and let go at the right moment. That last part, the right moment, is exactly where modes A and B part company.
Some keyers also remember a quick tap on the other lever made during an element, and send that element next even if you have already let go. This element memory is a different idea from mode A or B, and where a keyer has it, it forgives a tap that lands slightly early.
Mode A: what you hold is what you get
In mode A the keyer keeps alternating while both levers are closed, and when you release them it stops after the element it is sending. To send C, -.-., you squeeze with the dah lever first, hear dah, di, dah, and keep squeezing until the final dit has started. Then you let go and the dit finishes.
The rule of thumb for mode A: let go during the last element you want.
Let go one element early, during the second dah, and the keyer finishes that dah and stops. You have sent -.-, which is K. Hold on too long, into a fifth element, and you send -.-.-, which is not a letter at all.
Mode A is easy to reason about. The keyer never sends anything you are not holding (or did not tap), so when something comes out wrong, the cause is in your release.
Mode B: one more after you let go
In mode B a squeeze leaves a trace. Let go of both levers during an element and the keyer finishes that element, then adds one more, the opposite one. To send C in mode B you squeeze with the dah lever first and let go during the second dah: the keyer finishes that dah and then adds the final dit by itself.
The rule of thumb for mode B: let go during the element before the last one.
Here are the same characters keyed both ways:
| Character | Code | Mode A: let go during | Mode B: let go during |
|---|---|---|---|
| K | -.- |
the second dah | the dit |
| R | .-. |
the final dit | the dah |
| C | -.-. |
the final dit | the second dah |
| Period | .-.-.- |
the final dah | the third dit |
The extra element is not a fault; it is the design. Mode B lets your hand leave the paddle a beat sooner. That matters more as speed rises, because the window you are aiming for shrinks: at 30 WPM a dit lasts 40 milliseconds (1200 divided by 30), and letting go “during” one is a narrow target.
The cost is that mode B sends something you are no longer holding. If your squeeze lingers into an element you meant to be the last, you get one extra.
Why switching later is hard
Neither mode is better in the abstract. The trouble starts when your hand has learned one and the keyer is set to the other, because the release point becomes automatic. You stop deciding when to let go; your hand just does it.
The errors are predictable, and they mirror each other:
- A mode B hand on a mode A keyer drops the last element. C comes out as K,
-.-, and the period.-.-.-loses its final dah and turns into AR,.-.-.. - A mode A hand on a mode B keyer adds one. K comes out as C,
-.-., and C turns into-.-.-.
If you hear yourself sending K for C, or C for K, on someone else’s keyer, check the mode before you doubt your sending. And if you write the mode down for one keyer, write it for all of them: a radio’s built-in keyer and a separate box can easily be set differently.
So the usual advice comes down to one line: pick a mode early and keep it. Changing is possible, but it means unlearning a timing your hand performs without asking you.
Which one should you pick?
There is no wrong answer, but there are a few honest guides:
- If you never squeeze, it does not matter. Keyed one lever at a time, a dual-lever paddle sends the same Morse in A and B. That is also how a single-lever paddle always works; Single-lever vs dual-lever paddles compares the two.
- If you want the keyer to send only what you hold, choose A. Its mistakes are easy to trace, and a lingering squeeze cannot add anything.
- If you like to let go early, or you plan to send fast, try B. Its earlier release point gives you more room at speed.
- If you already squeeze in one mode, stay there. Set every keyer you use to match your hand, not the other way round.
To learn either one, slow the keyer down, perhaps to 15 WPM, and send the alternating characters from the first table until each comes out right ten times in a row. Then move to words built from them: CAR, RACK, CRANK. Every letter in CRANK is a single squeeze, which makes it a good test of your release timing.
Trying both modes on a Mac
You do not need a paddle to find out which mode suits your hand. Any two keys you can hold at once behave like a dual-lever paddle. Dot & Dash has paddles built in: by default the Left Option key sends dits and the Right Option key dahs, timed at the speed you set, in iambic mode A or B, chosen in Settings, General. In the app’s own words: “In mode B a squeeze adds one more element after you let go.” Its sending drill reads back what you keyed, so a C that came out as K shows up at once.
Questions
Is mode B faster than mode A?
No. The speed is set on the keyer and is the same in both modes. Mode B only lets you release a squeeze one element earlier; keyed correctly, both send identical Morse.
Does the mode matter if I only press one lever at a time?
No. Modes A and B differ only in what happens when you release a squeeze, so if you never close both levers together, they behave the same.
Can a single-lever paddle do iambic keying?
No. Its one lever cannot close both contacts at once, so there is never a squeeze. The keyer still times every dit and dah; you make each change between them yourself.
Why did my C turn into K on a friend’s keyer?
The usual cause is a hand trained on mode B meeting a keyer set to mode A, which does not add the final element your hand expects. Switch the keyer to B, or hold the squeeze until the last dit has started.