Frequency Wavelength Calculator
This calculator requires the
use of Javascript enabled and capable browsers. This calculator is
designed to calculate the wavelength of any frequency signal. Enter the
frequency number, by default 27.185, you wish to calculate and then
select the designator from those given in the table. The default is
megahertz. (27.185 megahertz is channel 19, the highway channel, of the
Citizens Band Radio Service. See our chart for other CB frequencies. You
may also wish to see other allocated US and International frequencies.)
Click the button for a measure of a full wave, three quarter wave, five
eights wave, half wave or quarter wave length. The length is returned in
U.S. values separately in feet and also in inches, as well as in metric
values of meters and millimeters. You may change the entered frequency
value or click on Clear Values to try again. Be sure to click on Full
Wave to see the actual frequency band designation and frequency
wavelength verified as the wavelength itself is displayed. The Frequency
Designation and Frequency Wavelength will vary according to the wave
selection. The obvious need for that information is that the Frequency
Wavelength is where you may expect to see harmonic or rf interference
from the broadcast Frequency Designation.
There are different ways to indicate where to find a certain station on
a radio dial. For example, we could say that a station is operating on
27185 kilohertz (kHz), 27.185 megahertz (MHz), or on 11 meters, which is
where the CB frequencies are. All three ways of expressing the frequency
are correct! Radio waves are transmitted as a series of cycles, also
known as hertz, one after the other. The hertz (abbreviated Hz) is equal
to one cycle per second. You may have noticed that the electric power
supplied to your home is rated at 60 Hz. Electric power is distributed
by the power company as alternating current (AC), meaning it goes
through a sine wave cycle of changing directions of flow. When we say
that electric power is 60 Hz, we mean it changes the direction of flow
(cycles or hertz) 60 times in one second. Radio waves go through far
more cycles in a second than electric current, and we need to use bigger
designation units to measure them. We have chosen to use the metric
system for such designations. One is the kilohertz (kHz), which is equal
to 1000 cycles per second. Another common one is the megahertz (MHz),
which is equal to 1,000,000 cycles per second, which is the equivalent
of also 1000 kHz. A gigahertz (GHz) is 1000 megahertz. The obvious
relationship between these units is typical of metric designation
changes, being a factor of 1000.
1,000,000
Hertz = 1000 Kilohertz = 1 Megahertz = .001 Gigahertz
Radio, in
various forms, is usually thought of beginning at frequencies of
approximately 5 kHz, though most commercially readily available receivers
only have the ability to tune frequencies down to about 150 kHz. The
generic term wavelength is left over from the very early days of radio.
Frequencies were measured in terms of the distance between the peaks of
two consecutive cycles of a radio wave instead of the number of cycles per
second. Hams still designate ranges of frequencies in the same manner.
Even though radio waves are invisible, there is a measurable distance
between the cycles of electromagnetic fields making up a radio wave. The
distance between the peaks of two consecutive cycles is measured in
meters, hence usage by hams. The relationship between a radio signal's
frequency and its wavelength can be found by the industry accepted formula
wavelength equals 300 divided by the frequency in megahertz.
Assuming the formula is correct, a frequency of 27185 kHz would be
equivalent to a wavelength of 11.035 meters (try it on the calculator but
be sure to click on Full Wave...), which we would round to 11 meters.
Thus, 27185 kHz, 27.185 MHz, and 11 meters as a broad group, all refer to
the same operating frequency! As the formula indicates, the wavelength of
a radio signal decreases as its frequency increases. This is important
because the length or height of various types of antennas must often be a
fraction (usually one-quarter or one-half) of the wavelength of the signal
to be transmitted or received. This means that most antennas designed for
frequencies near 4000 kHz will be physically considerably larger than
antennas designed for frequencies near 30 MHz. Other than in amateur
radio, frequencies are seldom given in terms of wavelength anymore. Hams
refer to certain segments of the shortwave bands are referred to in terms
of meter bands as a convenient form of shorthand. For example, the term
10-meter band is used to refer to the ham radio band that extends from
28000 to 29700 kHz.
There
are exceptions to the general rules as are evident in
the above frequency table. The 17-meter ham radio band
is actually higher in frequency than the 16-meter
broadcasting band. These deviations to guidelines are a
product of early mistakes in usage that are now accepted
as correct for the purpose of continuity of that
particular band.
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