High Frequency
High frequency (HF) radio frequencies are between 3 and 30 MHz. Also known as the decameter band or decameter wave as the wavelengths range from one to ten decameters (ten to one hundred metres). Frequencies immediately below HF are denoted medium frequency (MF), and the next higher frequencies are known as very high frequency (VHF). The HF band is a major part of the shortwave band of frequencies, so communication at these frequencies is often called shortwave radio. Because radio waves in this band can be reflected back to Earth by the ionosphere layer in the atmosphere, called "skip" or skywave propagation, these frequencies can be used for long distance communication, at intercontinental distances. The band is used by international shortwave broadcasting stations (2.310 - 25.820 MHz), aviation communication, government time stations, weather stations, amateur radio and citizens band services, among other uses.
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Famous quotes containing the words high and/or frequency:
“This is of the loon—I do not mean its laugh, but its looning,—is a long-drawn call, as it were, sometimes singularly human to my ear,—hoo-hoo-ooooo, like the hallooing of a man on a very high key, having thrown his voice into his head. I have heard a sound exactly like it when breathing heavily through my own nostrils, half awake at ten at night, suggesting my affinity to the loon; as if its language were but a dialect of my own, after all.”
—Henry David Thoreau (1817–1862)
“One is apt to be discouraged by the frequency with which Mr. Hardy has persuaded himself that a macabre subject is a poem in itself; that, if there be enough of death and the tomb in one’s theme, it needs no translation into art, the bold statement of it being sufficient.”
—Rebecca West (1892–1983)