Mediumwave

Mediumwave radio broadcaststhose betweenfrequencies500 kHz2000 kHz. In most ofworld, mediumwave serves asmost common bandbroadcasting. The standard AM broadcast band535 kHz1705 kHz.

Mediumwave signals havepropertiesfollowingcurvature ofearth (the groundwave)reflecting or refracting offionosphere at night (skywave). This makes this frequency idealboth localcontinent-wide service, depending ontimeday. For example, duringdayradio receiver instateMarylandablereceive reliable but weak signals from high-power stations WFAN, 660 kHz,WOR, 710 kHz, 400 kmNew York City, duegroundwave propagation. At night,same receiver picks up signals as far away as Mexico CityChicago reliably.

InAmericas, mediumwave stationsseparated by 10 kHzhave two sidebands+/- 5 kHz. Inrest ofworld,separation9 kHz,sidebands+/- 4.5 kHz. This provides adequate audio qualityvoice, butinsufficienthigh-fidelity broadcasting, whichreserved forVHF FM bands.

InUnited States,September 2002,Federal Communications Commission approvediBiquity in-band on-channel (IBOC) systemdigital broadcasting, whichmeantimproveaudio qualitysignals. The Digital Radio Mondiale (DRM) IBOC system has been approved byITUuse outsideAmericas.