| Abbreviation | Definition |
|---|---|
| Rx | Receiver |
| S21BR | Sierra Twenty one Bravo Romeo, Bangladesh |
| SAC | Send All Calls |
| SAR | Station Activity Report |
| SARA | Satellite Amateur Radio Astronomique |
| SARC | Schaumburg Amateur Radio Club |
| SARE | Sistema Auxiliar de Radioaficionados de Ejército (Spanish: Army Amateur Radio Auxiliary System) |
| SARL | Saskatchewan Amateur Radio League |
| SARL | South African Radio League |
| SAS | Steerable Antenna System |
| SB | Strong Bad signal |
| SBA | SideBand Addressing |
| SBARC | Santa Barbara Amateur Radio Club |
| SCA | Subsidiary Carrier Authorization |
| SCARC | Santa Clarita Amateur Radio Club |
| SCARC | Ski Country Amateur Radio Club |
| SCARC | St Charles Amateur Radio Club |
| SCARC | St Clair Amateur Radio Club |
| SCARC | Stanwood Camano Amateur Radio Club |
| SCARC | Sussex County Amateur Radio Club |