Javascript® Electronic Notebook by Martin E. Meserve Inverted-V Antenna Calculator
One characteristic of this configuration is that there is a shortening effect of the radiator element, by 3 to 5 percent. This will cause an antenna, that was initially meant for a dipole configuration, to require some pruning once installed.
Another characteristic is the lowering of the feed impedance. A standard dipole, at an appropriate height, will have a feed impedance of around 70 Ohms. Lowering the ends to ground, in the V configuration, reduces the feed impedance to near 50 Ohms. This can provide you with a better match than a standard dipole.
Yet another characteristic is the radiation pattern. A standard dipole generates a horizontal ratiation pattern in the shape of a figure 8, with maximum radiation broadside to the antenna. The Inverted-Vee tends to be more omni-directional and radiate equally in all directions.
For best results with this type of antenna, the Apex Angle should be kept between 70 and 110 Degrees. Below 70 Degrees the radiators start to become parallel to each other and signal canceling will start to occur. Above 110 Degrees the antenna starts looking like a standard dipole, minimizing any of the feed impedance and shortening effects. The optimum Apex Angle is 90 Degrees.
The Data Input section, below, is set up for you to enter data. You only have to fill in the text boxed with known data and the rest are calculated. You can choose to specify a frequency of operation and let the web page calculate and use that for the Radiator Element Length. Or, you can specify your own value for the Radiator Element Length. Any time you change any of the input data, the output data is automatically re-calculated.
A few things to note are:
Example: When this page is initially loaded, or when it is refreshed, the default Center Frequency is 7.100 MHz, the Reduction Percentage is 4.0%, and a End Insulator of 0' 8" (00.2 M) is assumed. With all the other entry areas cleared, a Apex Angle of 90° is also assumed. The program will then calculate a Radiator Element length of 31' 7-3/4" (9.64 M), a Mast Height of 22' 10-1/4" (6.96 M), and a Horizontal Space of 45' 8-1/4" (13.93 M).
The calculated information in the example is effectively the ideal setup for an Inverted-V. But usually you would have other specific requirements like a fixed Mast Height or a fixed Horizontal Space. Just enter your specific requirements in the area provided.
Start by entering the Center Frequency and the Reduction Percentage in the area provided on the left. This will then be used as a base for the other calculations. Then enter your other information in the areas provided on the right of the diagram.