List of abbreviations: 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