Morse code abbreviations
Morse code abbreviations differ from prosigns for Morse code in that they observe normal interletter spacing; that is, they are not "run together" the way prosigns are. From 1845 until well into the second half of the 20th century, commercial telegraphic code books were used to shorten telegrams, e.g. "Pascoela = Natives have plundered everything from the wreck".
|AA||All after (used after question mark to request a repetition)|
|AB||All before (similarly)|
|ARRL||American Radio Relay League|
|BK||Break (to pause transmission of a message, say)|
|BTU||Back to you|
|BUG||Semiautomatic mechanical key|
|BURO||Bureau (usually used in the phrase PLS QSL VIA BURO, "Please send QSL card via my local/national QSL bureau")|
|CL||Clear (I am closing my station)|
|CQ||Calling any station|
|CQD||Original International Distress Call, fell out of use before 1915|
|CUL||See you later|
|CW||Continuous wave (i.e., radiotelegraph)|
|DE||From (or "this is")|
|DSW||Goodbye (Russian: до свидания [Do svidanya])|
|DX||Distance (sometimes refers to long distance contact), foreign countries|
|FB||Fine business (Analogous to "OK")|
|FCC||Federal Communications Commission|
|GA||Good afternoon or Go ahead (depending on context)|
|GND||Ground (ground potential)|
|HEE||Humour intended (often repeated, e.g. HEE HEE)|
|HI||Humour intended (possibly derived from HEE)|
|II||I say again|
|KN||Over; only the station named should respond (e.g. W7PTH DE W1AW KN)|
|OM||Old man (any male amateur radio operator is an OM regardless of age)|
|OTC||Old timers club (ARRL-sponsored organization for radio amateurs first licensed 20 or more years ago)|
|OOTC||Old old timers club (organization for those whose first two-way radio contact occurred 40 or more years ago; separate from OTC and ARRL)|
|QCWA||Quarter Century Wireless Association (organization for radio amateurs who have been licensed for 25 or more years)|
|R||Are; received as transmitted (origin of "Roger"), or decimal point (depending on context)|
|RPT||Repeat or report (depending on context)|
|RST||Signal report format (Readability-Signal Strength-Tone)|
|SASE||Self-addressed, stamped envelope|
|SFR||So far (proword)|
|SIG||Signal or signature|
|SK||Out (proword), end of contact|
|SK||Silent Key (a deceased radio amateur)|
|SMS||Short message service|
|T||Zero (usually an elongated dah)|
|UR||Your or You're (depending on context)|
|WTC||Whats the craic? (Irish Language: [Conas atá tú?])|
|YL||Young lady (originally an unmarried female operator, now used for any female)|
|88||Love and kisses|
An amateur radio conversation in Morse code 
The skill to have sensible conversations with Morse is more than knowing just the alphabet. To make communication efficient, there are many internationally agreed patterns of communication.
A sample CW conversation between station 1 (S1) and station 2 (S2)
CQ CQ CQ DE S1 K Calling anyone (CQ), this is (DE) S1, listening for any response (K)
S1 DE S2 KN Calling S1, this is S2, listening for a response only from designated station (KN) (Two-way connection established)
S2 DE S1 = GA DR OM UR RST 5NN HR = QTH TIMBUKTU = OP IS JOHN = HW? S2 DE S1 KN Good afternoon dear old man. You are RST 599 here (the N's substitute for 9's; signal is very readable (5) and very strong (9), with very good tone (9)) I'm located in Timbuktu. The operator's name is John. How do you copy?
S1 DE S2 = TNX FB RPRT DR OM JOHN UR 559 = QTH HIMALAYA = NAME IS YETI S1 DE S2 KN Thanks for the nice (fine-business) report dear old man John. I read you 559 (very readable (5), average strength (5), very good tone (9)). I am in the Himalayas. My name is Yeti.
S2 DE S1 = OK TNX QSO DR YETI = 73 ES HPE CUAGN S2 DE S1 KN Okay, thanks for this conversation (QSO), dear Yeti. Best regards and hope to see you again.
S1 DE S2 = R TU CUAGN 73 S1 DE S2 SK Understood. Thank you. Best regards. (signing off)
With heavy use of the Q code and Morse Code Abbreviations, surprisingly meaningful conversations can be had. Note that very few English words have been used ("is" and "name"), only abbreviations. S1 and S2 might not speak the same native language.
Of course, real rag-chewing (lengthy conversations) cannot be done without a common language. On the worldwide amateur bands this is often English.
Contesters often use a very specialized and even shorter format for their contacts. Their purpose is to process as many contacts as possible in a limited time (e.g. 100-150 per hour).
See also 
- Commercial Telegraphic Code Books James A. (Jim) Reeds