The 40 Meter Inverted V Antenna
This 40 meter Inverted V antenna was tested and tuned at a height of 35 feet and proved excellent results. A distance of approximately 80 feet is required to tie off the ends of the antenna. The ends of the antenna are about 11 feet above the ground.
The antenna has a near perfect 50 ohm impedance and does not use a balun. This antenna is broad banded enough to work the entire 40 meter band with very low SWRs.
Inverted V antennas are used for working HF frequencies and are typically not suitable for VHF or UHF frequencies. These antennas are horizontally polarized. They are great for working long distance communications but also do a good job working closer stations that are normally heard during the daylight hours.
An inverted V antenna can be built using either stranded or solid gauge copper wire depending on the use and mounting conditions. Stranded wire is often used for antennas that are mounted in trees or in high wind areas where the wire elements are under a lot of stress. Solid gauge wire is suitable for mounting the antenna on a mast or tower as the antenna moves less in the wind and there is usually a lesser chance of a wire element kinking and breaking. The size of wire used for the elements also depends on the mounting conditions.
The video demonstrates construction techniques using 14 gauge solid insulated outdoor wire (14-1 AWG PE). In most cases either 14 or 12 gauge wire may be used. Wire size and types are discussed in the Dipole and Inverted V Antenna Basics video.
There is a formula for calculating the length of an inverted V antenna but I prefer to instead use the formula for a dipole antenna. When using the formula for a dipole antenna I find that my elements are just slightly long and usually never too short. So for making each element my formula is 234 / F (MHz) = Length (feet) + 20". This formula calculates one half of the antenna plus an extra length for connections.
The antenna is tuned the same way as tuning a regular dipole antenna. The lengths of the antenna elements are either lengthened or shortened until the length of the antenna is correct for the desired operating frequency. The length of both antenna elements must be equal. Changes made to one half of the antenna also need to be made to the other half.
When building your first inverted V antenna you might make the lengths of the elements slightly longer than as calculated in case of any extra needed length. Always remember to add 8" to 10" of extra wire on each end of the wire sections (16" to 20" total) for connecting the feed-point and insulators.