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A decametre (International spelling as used by the International Bureau of Weights and Measures and by most English speaking countries, [1] [2] United States spelling dekameter or decameter [3] [4]), symbol dam ("da" for the SI prefix deca-, [1] "m" for the SI unit metre), is a unit of length in the International System of Units (SI) equal to ten metres.
Nançay Decameter Array (DAM) Nançay, France 10–100 MHz DAM website (fr) Nançay Radio Heliographe (NRH) Nançay, France 150–450 MHz NRH website (fr) ALLBIN (Amateur Linked Long Baseline Interferometer Network) Germany
HF's position in the electromagnetic spectrum.. High frequency (HF) is the ITU designation [1] for the band of radio waves with frequency between 3 and 30 megahertz (MHz). It is also known as the decameter band or decameter wave as its wavelengths range from one to ten decameters (ten to one hundred meters).
Units in everyday use by country as of 2019 The history of the metric system began during the Age of Enlightenment with measures of length and weight derived from nature, along with their decimal multiples and fractions. The system became the standard of France and Europe within half a century. Other measures with unity ratios [Note 1] were added, and the system went on to be adopted across ...
The prefix was a part of the original metric system in 1795. It is not in very common usage, although the decapascal is occasionally used by audiologists.The decanewton is also encountered occasionally, probably because it is an SI approximation of the kilogram-force.
Radio astronomy emerged after the Second World War, when experts and surplus equipment became available for civilian use.The École Normale Superieure was given three 7.5 m diameter Würzburg Riese that the British had seized from the Germans during the war.
The length of the meter, for example, is given as 39.37 inches. The mean of the best English and the best American determinations differs from this only by about the amount by which the standard bar changes its length by a change of one degree of temperature.
The Observatory has been used for studying various aspects of the Sun, galaxies and pulsars. A few observations with the array have been the first two-dimensional images of radio emission from slowly varying discrete sources in the outer solar corona, an all-sky survey of radio sources at 34.5 MHz in the declination range -30° S to 60° N, and a low frequency carbon recombination lines in ...