Mellembølger

Ikke at forveksle med Mellemfrekvens (radioteknik).

Ikke at forveksle med Mellembølgebåndet.

Mellembølger, mellemfrekvens (forkortet MB eller MF fra engelsk medium frequency forkortet) og er radiobølger i området (fra men ikke med) 300 kHz – 3 MHz, der har følgende korresponderende bølgelængdeinterval i vakuum (fra men ikke med) 1 km - 100 m. Derfor kaldes mellembølger også hektometerbølger eller hectometerbølger.

Svaret på hvorfor disse radiobølger både kaldes ved deres bølgelængde i meter og frekvens i Hertz skyldes, at radiobølger i radiofoniens barndom før 1920'erne, kalder radiobølger ved deres bølgelængde i meter.^[1] Mellem ca. 1923 til 1960 anbefales det at angive radiobølgers frekvens i cycles-per-second (cps). Fra 1960 angives frekvens i Hertz.^[2]

Mellembølger omfatter mellembølgebåndet og noget af kortbølgebåndet.

Kilder/referencer

^ earlyradiohistory.us: Kilohertz to Meters Conversion Charts Citat: "...The general public, used to wavelengths, had to be coaxed into making the transition to frequencies, and it was a good fifteen years before you stopped seeing references to wavelengths in the U.S. (In Europe, where mediumwave stations are assigned in 9 khz steps, they still are commonly reported by wavelength). In 1923 many publications started to print conversion charts like the two listed above, with explanations about this newfangled frequency concept. However, there was one area of inconsistency, which explains why I've included two slightly different charts...", backup
^ November 18, 2016, edn.com: Cycles per second: A historical perspective Citat: "...In honor of Hertz's many contributions to the field of electrodynamics the General Conference on Weights and Measures (CGPM) in 1960 replaced the designation of cycles-per-second with hertz..."

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[1] rlyradiohistory.us: Kilohertz to Meters Conversion Charts Citat: "...The general public, used to wavelengths, had to be coaxed into making the transition to frequencies, and it was a good fifteen years before you stopped seeing references to wavelengths in the U.S. (In Europe, where mediumwave stations are assigned in 9 khz steps, they still are commonly reported by wavelength). In 1923 many publications started to print conversion charts like the two listed above, with explanations about this newfangled frequency concept. However, there was one area of inconsistency, which explains why I've included two slightly different charts...", backup

[2] November 18, 2016, edn.com: Cycles per second: A historical perspective Citat: "...In honor of Hertz's many contributions to the field of electrodynamics the General Conference on Weights and Measures (CGPM) in 1960 replaced the designation of cycles-per-second with hertz..."

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