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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 28185 kilohertz (kHz), 28.185 megahertz (MHz), 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 electrical 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.

For your reference:
1,000,000 Hertz = 1000 Kilohertz (1000 KHz) = 1 Megahertz (1 MHz) = .001 Gigahertz (.001 GHz)

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 (λ) 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. Amateur Radio Operators 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 Amateur Radio Operators. The relationship between a radio signal's frequency and its wavelength can be found by the industry accepted formula: λ = 300/Frequency in Megahertz.

Input frequency in mhz
Decimal Feet Decimal Inches Feet and Inches
For those who prefer to use tapes and rulers.
λ in meters
λ in cm
5/8λ in cm
1/2λ in cm
1/4λ in cm
1/6λ in cm
1/10λ in cm
4/3λ in cm
λ decimal ft
5/8λ decimal ft
1/2λ decimal ft
1/4λ decimal ft
1/6λ decimal ft
1/10λ decimal ft
4/3λ decimal ft
λ in inches
5/8λ in inches
1/2λ in inches
1/4λ in inches
1/6λ in inches
1/10λ in inches
4/3λ in inches
4/3λ (Hentenna circle)

To calculate electrical wavelength, change the velocity factor.
 Velocity Factor

Things to notice: try frequencies 149.9, 299.7, 494, and 983.5 with no velocity factor.
Try 142.38 284.8 and 468 with 95% end effect factor. Notice the resultant wavelengths.
These numbers should look familiar by now... :)