Abkürzungen "C"
| CARC | Cairns Amateur Radio Club |
| CARF | Canadian Amateur Radio Federation |
| CARS | Cyprus Amateur Radio Society |
| CASHOTA | Castles and Stately Homes on the Air  |
| CBARC | Citrus Belt Amateur Radio Club |
| CCAE | European Collins Collector Association |
| CDG | Croatian Digital Group |
| CDXC | Clipperton DX Club |
| CDXG | Charente DX Group |
| CEPT |
European Conference of Postal and Telecommunications Administrations |
| CHOTA |
Churches & Chapels on the Air |
| CIsA | Canadian Islands Awards |
| CISA | Castles in Serbia Awards |
| CISAR | Centro Italiano Sperimentazione Attivita Radiantistiche |
| CLHA | Croatian Lighthouse Award |
| COTA | Castles on the Air |
| COTA | Carabinieri on the Air |
| CPDXG | Chilean Pacific DX Group |
| CRA | China Radio Association |
| CRAC | Chinese Radio Amateur's Club |
| CRC | Czech Radio Club |
| CRD | Club Radio Durnal |
| CRRL | Canadian Radio Relay League |
| CRSA | Chinese Radio Sports Association |
| CSA | Canadian Space Agency |
| CSDXC | Czechoslovak DX Club |
| CTARL | Chinese Taipei Amateur Radio League |
| CUWS | Cambridge University Wireless Society |
| CWJF | Grupo Juizforano de CW |
| CWOPS | The CW Operator's Club |
