K in Morse code is —·—, written as -.-. Every licensed radio operator, aviation controller, and military communicator worldwide uses this exact pattern — it is the ITU-R M.1677-1 international standard, unchanged since the early 20th century.
Why K Has a 3-Signal Code
Alfred Vail designed the Morse code encoding in the 1830s by counting letter frequency in a printer's type case. Common letters got short codes; rare letters got long ones. K appears in roughly 0.8% of English text — the #22 most frequent letter — which determined its 3-signal code.
For comparison: E (the most common at 13%) gets one dot. Q (0.1%) gets four signals. The system is efficient by design — it was built for a world where telegraph operators were paid per word and transmission speed determined commercial value.
Memory Trick for K
DAH-dit-DAH — the OK rhythm.
Do not memorise what it looks like — memorise what it sounds like. Tap it on your desk while saying "dit" for dots and "dah" for dashes. Then use the Play button on the Translator and listen to K repeatedly. Your goal is to hear the pattern and think K with no intermediate step — the same automatic response you have when you hear spoken words.
In the NATO phonetic alphabet, K is spoken as "Kilo" on voice radio — chosen because it cannot be confused with any other letter name over a noisy channel.
Learning K With Related Letters
K (-.-) is a 3-signal letter. Other letters in this group: D, G, O, R, S, U, W. Learning letters by signal-length group is faster than learning them alphabetically — once your ear knows what 3 signals feels like, you only need to distinguish the pattern within the group.
The Learn page introduces K in Lesson 3 — added once the core alphabet is solid. Each lesson uses audio flashcards: hear the signal first, then identify the letter.
Words Starting With K
Practising letters inside real words builds stronger memory than drilling them in isolation. Use the Translator to hear any of these words at adjustable WPM — start at 5 WPM and increase as each speed becomes comfortable.
Sending K in the Two-Button Practice Mode
In the Two-Button Practice mode, left button = dot, right button = dash. To send K: right → left → right.
The gap between signals within K is one unit. The gap after K before the next letter is three units. Between words, seven units. These ratios must be consistent — incorrect timing makes even correct patterns ambiguous to a receiver.
Real-World Uses of K in Morse Communication
K-prefix callsigns (United States). KW (kilowatt power) and K (invitation to transmit) both common in CW.
If you are studying for an amateur radio licence or planning on-air CW operation, K will appear constantly. The Ham Radio Morse Code guide covers the full path from learning to operating, including how callsign identification works and what to expect in a standard CW contact.
A Practice Plan for K
Spaced repetition — returning to the same material at increasing intervals — is the most efficient way to build durable recognition:
- Day 1: Learn K (-.-) — audio only, use the Translator, 10 minutes
- Day 2: Drill K alongside one letter you already know in Practice mode
- Day 4: Practise K in words — type words starting with K in the Translator
- Day 7: Test recognition speed in the Quiz — K appears from Level 3 onward
The target: hear DAH-dit-DAH and think K before your conscious mind has processed it. That automatic response is what makes Morse code usable at real operating speeds.
K — The Invitation
K (—·—) is the mirror image of C (—·—·) with the final dot removed: two dashes with a dot between them. The symmetric structure — long-short-long — is easy to remember as "the symmetric letter". In CW procedure, K alone means "invitation to transmit" — the equivalent of "over" in voice radio. At the end of a transmission, sending K means "any station may respond". It is one of the most transmitted single letters in amateur radio. Every CQ call ends with K. Mastering K is essential for any on-air Morse operation.
K-prefix callsigns (K, KA, KB, KC, KD, KE, KF, KG, KH, KI, KJ, KK, KL, KM, KN, KO, KP, KR, KS, KT, KV, KW, KX, KY, KZ) are United States amateur stations — one of the largest callsign groups in the world. Hearing K in callsigns is extremely common in any US-facing CW contact.
From Learning K to Real Morse Communication
Knowing K (-.-) is one piece of a larger picture. The Learn page introduces K in the context of related letters — you never drill it in total isolation. The Two-Button mode presents K randomly alongside other letters you know, forcing genuine recognition rather than sequential anticipation. The timed Quiz tests whether you can identify K quickly enough to be useful in real communication.
At 0.8% frequency (#22 most common letter), K appears occasionally in any Morse text. Solid K recognition rounds out your alphabet and ensures you can handle any text, even if K appears rarely.
Use the Translator to hear K in context — type words containing K and listen at 8–12 WPM. The Alphabet page shows K alongside every other character for reference. The Abbreviations page covers the Q-codes and CW shorthand where K appears in operational contexts.