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Understanding Radio
Frequencies
Radio waves are a form
of electromagnetic radiation, created whenever a charged object (for
example, in normal radio transmission, an electron) accelerates with a
frequency that lies in the radio frequency (RF) portion of the
electromagnetic spectrum. In radio, this acceleration is caused by
alternating current input to an antenna. Radio frequencies occupy the
range from a few tens of hertz (cycles per second) to 300 gigahertz (300
billion cycles per second). Nonetheless, most commercial applications
use only a portion of this spectrum.
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The Radio Spectrum |
|
ELF |
SLF |
ULF |
VLF |
LF |
MF |
HF |
VHF |
UHF |
SHF |
EHF |
|
3 Hz
to
30 Hz |
30 Hz
to
300 Hz |
300 Hz
to
3k Hz |
3k Hz
to
30 kHz |
30 kHz
to
300 kHz |
300 kHz
to
3 MHz |
3 MHz
to
30 MHz |
30 MHz
to
300 MHz |
300 MHz
to
3 GHz |
3 GHz
to
30 GHz |
30 GHz
to
300 GHz |
Other types of
electromagnetic radiation, with frequencies above the RF range, are
microwave, ultra-violet, visible light, near- and far-infrared, X-ray,
gamma-ray and cosmic-ray. Since the energy of an individual photon at
radio frequency speed is too low to remove an electron from its atom,
radio waves are classified as non-ionizing radiation.
Radio Frequency, or RF, refers to that portion of the electromagnetic
spectrum in which electromagnetic waves can be generated by alternating
current fed into an antenna. Such frequencies, and their corresponding
wavelengths, account for the following parts of the spectrum shown in
the chart below.
The
gradient of colors illustrates the visible-light portion of the
electromagnetic spectrum.
Visible light waves are
the only electromagnetic waves we can see. We see these waves as the
colors of the rainbow (violet, blue, green, yellow, orange, red). Each
color has a different wavelength. Red has the longest wavelength and
violet has the shortest . When all the waves are seen combined together,
they make white light (artificial or sunlight). The visible or
white-light portion of the electromagnetic spectrum ranges in
wavelengths (or frequencies) from approximately 300 nanometers to about
700 nanometers. One nanometer is equal to one billionth (10-9) of a
meter.
The table above shows the commercial applications used in the various
regions of the RF spectrum. The bar at the top of the table shows the
descending order, left-to-right (by frequency) of the regions of the RF
spectrum.
Click here for a short guide to popular RF connectors.
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