Dipole Calculator
Calculate dipole antenna length, wavelength, and dimensions for optimal radio frequency performance
Calculate Dipole Antenna Dimensions
The frequency at which the antenna will operate
Use adjustment factor for high frequencies and thick conductors
Example Calculation
FM Radio Dipole (98.5 MHz)
Frequency: 98.5 MHz
Application: FM radio reception
Expected length: ~1.52 meters total
Calculation Steps
L = 468 / 98.5 = 4.751 feet
L = 4.751 × 0.3048 = 1.448 meters
Arm length = 1.448 / 2 = 0.724 meters
Result: Each arm = 72.4 cm
Common Frequency Bands
Construction Tips
Cut wire 5% longer, then trim for best SWR
Use insulators at both ends and center
Keep antenna away from metal objects
Use 50Ω coaxial cable for feedline
Height above ground affects performance
Understanding Dipole Antennas
What is a Dipole Antenna?
A dipole antenna is the simplest and most fundamental type of antenna. It consists of two conducting elements (poles) separated by an insulator at the center. The total length is typically half the wavelength of the operating frequency.
Why Half-Wavelength?
The half-wavelength dipole is resonant at the design frequency, meaning it has optimal impedance characteristics (approximately 73 ohms) and maximum radiation efficiency. This makes it an excellent reference antenna for gain measurements.
Radiation Pattern
- •Maximum radiation perpendicular to the antenna
- •Nulls along the antenna axis
- •Doughnut-shaped 3D pattern
Calculation Formulas
Basic Formula
L = 468 / f (MHz) [feet]
L = 142.6 / f (MHz) [meters]
l = L / 2 (arm length)
Wavelength Formula
λ = c / f
c = 299,792,458 m/s
Dipole length ≈ λ/2
Adjustment Factor
k = 0.9787 - [11.86497 / (1 + (R/0.000449)^1.7925)^0.3]
R = (λ/2) / conductor_diameter
Note: The adjustment factor k accounts for the finite conductor diameter and becomes important at higher frequencies or with thicker conductors.