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Leg Lengths: Inverted V vs Horizontal Dipole Antennas

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  The halfwave dipole antenna element lengths are measured differently when building an inverted V dipole. You usually make an inverted-V dipole slightly shorter than a flat horizontal half-wave dipole because the downward-sloping legs change the antenna's capacitance and feed point impedance. A common rule of thumb is: Horizontal half-wave dipole: Each leg: Inverted-V dipole: Start with 2–5% shorter than the horizontal calculation, then trim while checking resonance. A practical formula is: or Example: 20 meters (14.2 MHz) Horizontal dipole: Total: Each leg: Inverted V: Total: Each leg: That's about 3.4 inches shorter per leg . Why? When the legs slope downward: The ends are closer to ground. The antenna has greater end capacitance. It becomes electrically longer than the same physical wire length. Therefore, less wire is needed to resonate at the same frequency. ...
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Half-wave Dipole Antenna Calculator

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  The measurements below are for building a simple Dipole Antenna. The Wire Size can range from 18 AWG to 12 AWG. The larger the wire, the wider the bandwidth. The antenna is designed to be fed with 50 or 75 Ohm Coax Cable of most any length with a Balun. Place a 1:1 Balun on the Antenna end of the Feedline. The Balun matches the Balanced Antenna into the Unbalanced Coax Cable. The balun will keep stray antenna currents off of the Feedline and help to keep stray RF out of the Radio Shack. If a Ferrite Balun is used, the balun needs to be rated at least twice the operating wattage to prevent the balun from overheating. This will help mitigate mismatches and stray RF due to using the antenna at frequencies other than what the antenna was specifically designed for. For a dipole antenna constructed to resonate at a desired center frequency ( cf) calculate the antenna length by using the formula: L = 468 / cf ( cf is in MHz). To determine the two element lengths ( E ), divide L / 2 ...
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