RST and 5NN: signal reports in Morse code explained
An RST report is three figures that tell the other operator how their signal reaches you: R for readability, from 1 to 5, S for strength, from 1 to 9, and T for tone, from 1 to 9. 599 is the top report: perfectly readable, extremely strong, a perfect tone. 5NN is the same 599 sent with cut numbers, N standing in for 9, and it is what you often hear in contests, where every second counts.
The report is the first real information in most CW contacts, right after the callsigns, so it is worth knowing what each figure means and how to give one that is useful.
What R, S and T stand for
Each figure answers its own question, and the three are independent.
Readability, 1 to 5: how hard is it to copy?
| R | Meaning |
|---|---|
| 1 | Unreadable |
| 2 | Barely readable, a word here and there |
| 3 | Readable with considerable difficulty |
| 4 | Readable with practically no difficulty |
| 5 | Perfectly readable |
Strength, 1 to 9: how loud is it? The scale runs from 1, faint signals that are barely there, through 3 (weak), 5 (fairly good) and 7 (moderately strong), to 9, extremely strong. Many receivers have a meter marked in these S units, and you can read the figure from it, or judge it by ear.
Tone, 1 to 9: how clean is the note? Low figures describe a rough, buzzing note, the sound of a transmitter with a badly filtered power supply. A 9 is a pure, steady tone with no ripple or warble. Most modern transmitters have a clean note, so 9 is the usual figure, and a lower one is worth taking seriously: it tells the other operator something in their station may need a look.
On voice, operators usually give only the first two figures, such as “five nine”, because the tone figure describes the note of a CW signal.
Reading a report
The figures are read one at a time, not as a number: 579 is “five seven nine”, not five hundred and seventy-nine. Some real reports and what they say:
| Report | What it means |
|---|---|
| 599 | Perfectly readable, extremely strong, perfect tone |
| 579 | Perfectly readable, moderately strong, perfect tone |
| 559 | Perfectly readable, fairly good strength, perfect tone |
| 449 | Readable with practically no difficulty, fair strength |
| 339 | Readable with considerable difficulty, weak |
| 539 | Perfectly readable, but weak |
| 399 | Extremely strong, but hard to copy |
The last two show why R and S are separate. A weak signal on a quiet band can be perfectly readable, so it earns R5 with S3. A strong signal buried under other stations or static can be loud and still hard to copy, so it earns S9 with R3. If you want to say why, the Q codes do it in three letters: QRM is interference from other stations, QRN is static, and QSB is fading. Q codes in Morse code: QTH, QSL, QRS and more has the rest.
A report below 599 is not a complaint. A 559 is a perfectly good contact, and an honest report is more useful to the other operator than an automatic 599: it tells them how their antenna, their power and the band are doing right now.
Sending a report in an ordinary contact
In a relaxed contact the report goes in your first over, usually after UR RST (“your signal report”) and usually twice, because figures have no context to guess from:
UR RST 579 579
..- .-. / .-. ... - / ..... --... ----. / ..... --... ----.
Every figure is five elements long, which is what makes reports harder to copy than words: there is no shortcut and no guessing. 5 is five dits, ....., di-di-di-di-dit. 7 is --..., and 9 is ----., four dahs and a dit. If figures still make you count, Morse code numbers 0 to 9 and the pattern behind them is the place to fix that first. Where the report sits in a full contact is shown in How a basic CW contact works, from CQ to 73.
To give a report, judge R first, by how much effort copying takes. Then S, from the meter or by ear. Then T, which is usually 9.
Why contests send 5NN
In a contest the aim is to make as many contacts as possible, and the report is often a formality: many exchanges simply give 599, and the part that matters is what comes after it. Sending 599 in full every time would waste air, so operators shorten it with cut numbers.
A cut number replaces a long figure with a short letter. The usual ones are N for 9 and T for 0, and A for 1 is common too. In a report, the one you will hear is N, in 5NN:
| Figure | Full code | Cut | Cut code |
|---|---|---|---|
| 9 | ----. |
N | -. |
| 0 | ----- |
T | - |
| 1 | .---- |
A | .- |
Each cut keeps part of the figure’s shape: N is the last dah and dit of 9, T is one dah of 0, and A is the first dit and dah of 1. That makes them easy to learn.
The saving is real. Counted in units, with the gaps inside and between the characters:
| Sent | Morse | Units | At 30 WPM |
|---|---|---|---|
| 599 | ..... ----. ----. |
49 | 1.96 seconds |
| 5NN | ..... -. -. |
25 | 1.00 second |
5NN takes about half the time of 599. At 30 WPM that saves about a second each time it is sent, and over a long contest the seconds add up. By ear, 5NN is a quick di-di-di-di-dit dah-dit dah-dit that you soon hear as one shape rather than three characters.
Copying cut numbers without confusion
A cut number is only a figure because of where it sits. N, -., is a letter anywhere else; in the report slot it means 9. So the trick to copying contest exchanges is to know the exchange before you hear it: if you expect a report followed by a number, you will read ..... -. -. as 599 without a pause.
When you write it down, write what you hear, 5NN, and read it as 599 afterwards. Converting while you copy splits your attention at the exact moment the next character arrives.
Outside contests, use cut numbers only where the other operator will expect them. In a slow, friendly contact with a newer operator, full figures are kinder.
Practicing reports by ear
Reports are a good first target for practice because they are short and they come in nearly every contact. Take a list of reports, from 339 to 599, have a friend or a practice file send them, and copy them at a speed where the figures come quickly; then mix in 5NN until you read it as 599 without thinking. Send them too, paying attention to the gap after each figure, because three five-element characters run together easily.
On a Mac, Dot & Dash can help with the listening half: its Text to Morse turns a line like UR RST 579 579 into Morse and plays it on its machine, and its Reference plays any figure when you rest the pointer on it. Once you have learned the figures, its Practice also has a Callsigns drill of made-up callsigns, which mix letters and figures as an exchange does, to key yourself or to copy by ear.
Questions
What does 599 mean in Morse code?
It is a signal report: readability 5 out of 5 (perfectly readable), strength 9 out of 9 (extremely strong) and tone 9 out of 9 (a perfect tone). It is the best report you can give.
Is 5NN the same as 599?
Yes. 5NN is 599 sent with cut numbers, where N stands for 9. It means exactly the same thing and takes about half as long to send.
Why do contests send 5NN so often?
In many contests the report is a formality, and the information that counts is the rest of the exchange. A fixed report, sent as 5NN, keeps each contact quick and predictable.
Is a report like 559 bad?
No. A 559 means perfectly readable at a fairly good strength with a clean tone, which is a perfectly good contact. Honest reports below 599 are normal and more useful than an automatic one.