Morse letters that sound alike, and how to tell them apart
The Morse letters that are easy to confuse fall into two families. Some differ by one more dit or dah: I, S, H and 5, U and V, D and B, M and O. Others use the same elements in a different order, or with dits and dahs swapped: A and N, G and W, K and R. You tell them apart by hearing each letter as one whole sound at full speed, never by counting its parts, and by drilling each pair side by side once you know both letters well.
The usual suspects
| Letters | Codes | Rhythm | What changes |
|---|---|---|---|
| I, S, H, 5 | .. ... .... ..... |
di-dit up to di-di-di-di-dit | one more dit each step |
| U, V | ..- ...- |
di-di-dah, di-di-di-dah | one more dit before the dah |
| D, B | -.. -... |
dah-di-dit, dah-di-di-dit | one more dit after the dah |
| M, O | -- --- |
dah-dah, dah-dah-dah | one more dah |
| A, N | .- -. |
di-dah, dah-dit | same elements, reversed |
| G, W | --. .-- |
dah-dah-dit, di-dah-dah | same elements, reversed |
| K, R | -.- .-. |
dah-di-dah, di-dah-dit | dits and dahs swapped |
The figures stretch some of these families further. After H comes 5, ...... After V comes 4, ....-. After B comes 6, -..... After J, .---, comes 1, .----, and after Z, --.., comes 7, --.... So a learner who has just settled S and H meets the same problem again, one dit longer, when the figures arrive.
Why these pairs trip the ear
Dit runs invite counting. At 5 WPM you can count the dits in S and H and get the right answer. At 20 WPM, H lasts 420 milliseconds and 5 lasts 540. The difference is one dit and one gap, 120 ms in all, which is too short to count reliably while you are also listening for the next letter. What helps instead is hearing each run as its own texture. One way to describe them: S sounds like a quick triplet, H like a short buzz, 5 like a slightly longer buzz. Counting asks “three or four?” when the question your ear needs to answer is “S or H?”
Reversed pairs lose their order. It is easy to register “one dit and one dah” and lose which came first, but in A and N the order is the whole message. The same goes for G and W. If you met A and N in the same session, they can fuse into one uncertain sound that you have to untangle later.
Swapped pairs share a shape. K is long, short, long. R is short, long, short. Both are three alternating elements, and on a tired evening the pattern “alternating, three” can be all that registers.
Your sending feeds your listening. If your hand adds a dit, you send H for S and rehearse the mistake every time. Spacing errors make false look-alikes too: squeeze the gap in AN, .- -., and it becomes P, .--.. Why your Morse letters run together covers that side of it.
Learn them apart, then drill them together
The fix has two stages, and the order matters.
- Never learn both halves of a pair in one session. Learn S until it is automatic, then add H in a later session. A good learning order keeps look-alikes apart for exactly this reason, so each letter gets to be its own sound before it has a rival.
- Once both are solid, put them side by side. A contrast drill is a random string of only the two letters, sent at full character speed, and you name each as it arrives. A practice partner can send it, or a trainer that lets you choose the characters can play it. With no partner, toss a coin to write a random list of the two letters, key it while you record yourself, and copy the recording a day later, once you have forgotten the order.
- Then widen the mix. Add the pair’s neighbors: S and H with I and 5, U and V with 4. The goal is to hear each letter as itself, not as “the other one”.
- Use words that hold both letters. Words make you switch fast, in context:
| Pair | Words to practice |
|---|---|
| S, H | SHE, HIS, HISS, SHH |
| A, N | AND, NAN, BANANA |
| U, V | VALUE, VAGUE |
| D, B | BED, BAD, DAB, BID |
| M, O | MOON, ROOM, MOM |
| G, W | GLOW, WAG, WIG |
| K, R | RAKE, TREK, RINK |
- Keep the character speed up. Use Farnsworth spacing so each letter is sent at 15 to 20 WPM while the gaps give you time to answer. Slow characters bring back counting.
- Answer straight away. If you hesitate, write a mark and move on. A pause to think about whether it was three dits or four is counting again.
Tricks for specific pairs
A and N. Listen for where the weight falls. A ends on the long sound, di-DAH; N starts on it, DAH-dit. Say them aloud with the stress in place and the difference becomes obvious.
G and W. The same idea: you can hear G as leaning forward, DAH-dah-dit, and W as landing at the end, di-dah-DAH.
K and R. K begins and ends with a dah, so it feels open and firm. R begins and ends with a dit and feels like a quick roll with a long note in the middle. K also turns up alone at the end of a radio transmission, meaning “over”, which gives it a sound of its own if you listen to on-air Morse.
M and O. O is noticeably long: 11 units against M’s 7. If a letter of dahs feels like it is still going, it is O. Five dahs in a row, -----, is 0.
D and B, U and V. Each pair differs by one dit, so treat the longer one as a separate word: you can hear a gallop in dah-di-di-dit that dah-di-dit lacks.
I, S, H and 5. Context helps here. Figures turn up in predictable places, such as callsigns, times and signal reports, so a buzz in the middle of a word is far more likely to be H than 5.
Check your sending
If you swap a pair when you listen, check whether you also swap it when you send. Key a line of words that contain the pair and let a decoder read it back; it only knows what your timing tells it. If it prints H where you meant S, your hand is adding a dit, and your ear has been learning from your hand. How to practice sending Morse code on your own has ways to get an honest read.
Dot & Dash is built with these pairs in mind. Its course keeps I, S, H and 5, A and N, U and V, D and B, and M and O at least a chapter apart, so each settles before you meet its twin. Along the way, the daily review brings the characters you miss back sooner, and Progress shows your accuracy for every character, so a stubborn pair is easy to spot.
Questions
Why do I keep mixing up S and H?
Often because you are counting the dits instead of hearing the letter. Raise the character speed so counting stops working, and drill S and H together once you know each one on its own.
Should I learn A and N at the same time?
It is better not to. Learn one until you answer it instantly, then add the other in a later session, and only then drill the two side by side.
What is the difference between a reversed pair and a swapped pair?
A reversed pair has the same elements in the opposite order, like A, .-, and N, -.. A swapped pair keeps the order but turns every dit into a dah and every dah into a dit, like K, -.-, and R, .-..
How do I tell 5 from H at speed?
Hear 5 as a longer buzz than H rather than counting five dits against four, and use context: figures turn up in predictable places, such as callsigns, times and signal reports.