These abbreviations are typically used when transmitting in Morse code in order to diminish the number of characters sent. Some of them are in use also in normal amateur radio speech.
| AA | All after (used after question mark to request a repetition) | OO | Official observer |
| AB | All before (similarly) | OP | Operator |
| ARRL | American Radio Relay League | OT | Old timer |
| ABT | About | OTC | Old timers club |
| ADR | Address | OOTC | Old old timers club |
| AGN | Again | PSE | Please |
| ANT | Antenna | PWR | Power |
| ARND | Around | PX | Prefix |
| BCI | Broadcast interference | QCWA | Quarter Century Wireless Association |
| BK | Break (to pause transmission of a message, say) | R | Are; received as transmitted (origin of “Roger”), or decimal point (depending on context) |
| BN | All between | RCVR | Receiver (radio) |
| BTR | Better | RFI | Radio Frequency Interference |
| BUG | Semiautomatic mechanical key | RIG | Radio apparatus |
| B4 | Before | RPT | Repeat or report (depending on context) |
| C | Yes; correct | RPRT | Report |
| CBA | Callbook address | RST | Signal report format (Readability-Signal Strength-Tone) |
| CFM | Confirm | RTTY | Radioteletype |
| CK | Check | RX | Receiver |
| CL | Clear (I am closing my station) | SAE | Self-addressed envelope |
| CLG | Calling | SASE | Self-addressed, stamped envelope |
| CQ | Calling any station | SED | Said |
| CQD | Original International Distress Call | SEZ | Says |
| CS | Callsign | SFR | So far (proword) |
| CTL | Control | SIG | Signal or signature |
| CUD | Could | SIGS | Signals |
| CUL | See you later | SK | Out (proword) |
| CUZ | Because | SKED | Schedule |
| CW | Continuous wave (i.e., radiotelgraph) | SMS | Short message service |
| CX | Conditions | SN | Soon |
| DE | From (or “this is”) | SNR | Signal-to-noise ratio |
| DN | Down | SRI | Sorry |
| DR | Dear | SSB | Single sideband |
| DSW | Goodbye (Russian: до свидания [Do svidanya]) | STN | Station |
| DX | Distance (sometimes refers to long distance contact), foreign countries | T | Zero |
| EMRG | Emergency | TEMP | Temperature |
| ENUF | Enough | TFC | Traffic |
| ES | And | TKS | Thanks |
| FB | Fine business (Analogous to “OK”) | TMW | Tomorrow |
| FCC | Federal Communications Commission | TNX | Thanks |
| FER | For | TT | That |
| FM | From | TU | Thank you |
| FREQ | Frequency | TVI | Television interference |
| FWD | Forward | TX | Transmit, transmitter |
| GA | Good afternoon or Go ahead (depending on context) | TXT | Text |
| GE | Good evening | U | You |
| GG | Going | UR | Your or You’re (depending on context) |
| GM | Good morning | URS | Yours |
| GN | Good night | VX | Voice; phone |
| GND | Ground (ground potential) | VY | Very |
| GUD | Good | W | Watts |
| GX | Ground | WA | Word after |
| HI | Laughter | WB | Word before |
| HR | Here, hear | WC | Wilco |
| HV | Have | WDS | Words |
| HW | How | WID | With |
| II | I say again | WKD | Worked |
| IMP | Impedance | WKG | Working |
| KN | Over | WL | Will |
| LID | Poor operator | WUD | Would |
| MILS | Milliamperes | WTC | Whats the craic? (Irish Language: [Conas atá tú?]) |
| MNI | Many | WX | Weather |
| MSG | Message | XCVR | Transceiver |
| N | No; nine | XMTR | Transmitter |
| NIL | Nothing | XYL | Wife |
| NR | Number | YF | Wife |
| NW | Now | YL | Young lady (used for any female) |
| NX | Noise; noisy | ZX | Zero beat |
| OB | Old boy | 73 | Best regards |
| OC | Old chap | 88 | Love and kisses |
| OM | Old man (any male amateur radio operator is an OM) |
Source: https://en.wikipedia.org/wiki/Morse_code_abbreviations