Inverted Vee Dipole Antenna Calculator

Input Center Frequency (in MHz) Inverted Vee Dipole Length Calculation

Input Center Frequency : in MHz (MegaHertz)

  
Length  : feet
 
  

The inverted-vee dipole is a half-wavelength antenna fed in the center like a dipole. By the rigorous definition, the inverted-vee is merely a variation on the dipole theme. But in this form of antenna as figure, the center is elevated as high as possi- ble from the earth's surface, but the ends droop to very close to the surface. Angle a can be almost anything convenient, provided that a > 90 degrees; typically, most in- verted-vee antennas use an angle of about 120 degrees.

Although essentially a com- pensation antenna for use when the dipole is not practical, many operators believe that it is essentially a better performer on 40 and 80 m in cases where the dipole can- not be mounted at a half -wavelength (64 ft or so) . By sloping the antenna elements down from the horizontal to an angle as shown in Figure, the resonant frequency is effectively lowered. Thus, the antenna will need to be shorter for any given frequency than a dipole. There is no absolutely rig- orous equation for calculation of the overall length of the antenna elements.

Although the concept of "absolute" length does not hold for regular dipoles, it is even less viable for the inverted-vee. There is, however, a rule of thumb that can be fol- lowed for a starting point: Make the antenna about 6 percent shorter than a dipole for the same frequency. The initial cut of the antenna element lengths (each quarter wavelength) is After this length is determined, the actual length is found from the same cut- and-try method used to tune the dipole in the previous section.

Bending the elements downward also changes the feedpoint impedance of the antenna and narrows its bandwidth. Thus, some adjustment in these departments is in order. You might want to use an impedance matching scheme at the feedpoint, or an antenna tuner at the transmitter.