O
| OB | Outside Broadcasting | OECD | Organization for Economic Co-operation and Development | OFCOM | Federal Office of Communications (Switzerland) | OFCOM | Office of Communications (GB) | OFDM | Orthogonal Frequency Division Multiplex | OFR | Off Frequency Rejection | OIR | Organisation internationale de radiodiffusion | OQPSK | Offset QPSK | OR | Off-Route | ORB | Orbit (used in the designation of certain WARCs) | OSCAR | Orbiting Satellite Carrying Amateur Radio | OTH | Over-the-Horizon | |