| 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 |
|
|
