Introduction

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.

Program Description

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:

• The equations behind this web page are really just a geometric solution, so, this page can be used with any type of wire antenna, dipole, trap-dipole, folded-dipole, etc..
• It's OK to mix and match dimensions. The web page does all calculations in US/Imperial measurements and converts on input and output, as necessary.
• The Radiator Arm (Ra) length, in the diagram, is measured from the Apex to the top of the End Support and thus includes the Radiating Element AND the End Insulator. The Input Data area provides space for specifying them both separately.
• If the Support Height (Hs) is not set or set to zero, a small height (0.001 Ft) is assumed to avoid some divide-by-zero problems.
• If you select any of the Check Boxes, some of the input data areas will be grayed out and not allow any input. To re-enable these input area Un-Check the appropriate Check Box.
• If too much data is left undefined, the program will start to make some assumptions. It may be benificial to start this way, see what the program comes up with, and then adjust the input data. For example, if you only define the Radiator Element and End Insulator length, the web page will assume a Apex Angle of 90 Degrees and calculate the rest of the information. You can then make changes as you see fit.
• I tried to intercept all possible entry configurations and error conditions but a few still remain. I will fix them when I get around to it but if there is something that really bothers you, send me email.

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.

Inverted-V Antenna Calculator

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.