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Wednesday, March 10, 2010

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Dipole Calculator
Most hams are familar with the center fed, half wave dipoles and inverted vees that are very popular and easy to build. This formula will give you a starting point to make these antennas. There are several factors that affect the resonant frequency of any antenna. Some of these factors are: the height above ground, the diameter of the wire, nearby structures, the affects of other antennas in the area and even the conductivity of the soil.

There is a standard formula that can be used as a starting point in your design. For a center fed, wire dipole, this formula is 468 / frequency in megahertz. You should always cut the antenna a few inches longer to allow you trim the antenna in order to obtain a 1:1 match.

The Inverted V should be about 3 - 5% shorter than a dipole at the same frequency. The calculator uses 4% as a constant in the calculation. You may change this value to any number that you would like to use.

This page uses the standard formula, 468 / f MHz to calculate dipole lengths. You may change this number to 234 for a 1/4 wave version.
Enter the formula for the antenna calculation

Divided by Freq MHz

Percent smaller for the Inverted Vee
Your dipole's total length is feet
Each leg of the dipole is feet
Your Inverted V's total length is feet
Each leg of the Inverted V is feet

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