RF3 Element Yagi Antenna Calculator
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This page covers a 3-element Yagi Antenna calculator, explaining the formulas and basics behind it. Calculators for other antenna types, such as parabolic, horn, dipole, and patch antennas, are also mentioned.
What is a Yagi Antenna?
The simple Yagi Antenna is shown in Figure 1. It consists of three elements: the director, the dipole, and the reflector. It may have one or multiple directors.
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Dipole (Driven Element): This is the feed point where the feedline is typically attached from the transmitter. It facilitates the transfer of energy from the transmitter module to the antenna. The feed point is located at the center of the driven element. It becomes resonant when its electrical length is about half of the wavelength of the operating frequency.
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Director: Designed primarily for receiving EM waves, it’s the shortest of the parasitic elements. Its length is approximately 5% shorter compared to the driven element and has a higher resonant frequency. The director helps achieve the desired gain and directional pattern. The spacing between directors usually ranges from 0.1λ to 0.5λ or more. The gain of a Yagi antenna depends on the length of the antenna array and not on the number of directors used.
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Reflector: Placed at the rear of the dipole or driven element. Its length is usually 5% longer compared to the driven element. The spacing of the reflector from the driven element is about 0.1λ to 0.25λ. The spacing also depends on bandwidth, gain, front-to-back ratio, and sidelobe pattern specifications.
The following specifications are crucial in selecting a Yagi Antenna and performing calculations using this Yagi antenna calculator:
- Bandwidth
- Impedance
- Gain
- Front-to-Back Ratio
Yagi Antenna Calculator Example
INPUT: Operating Frequency (MHz) = 200
OUTPUTS:
- Reflector Length = 0.7425 meters
- Dipole Length = 0.7095 meters
- Director Length = 0.66 meters
- Reflector to Dipole Spacing = 0.1875 meters
- Dipole to Director Spacing = 0.1875 meters
Formula/Equations Used in Yagi Antenna Calculator
The following formulas/equations are used in the Yagi Antenna Calculator:
This 3-element Yagi Antenna calculator is useful for designing Yagi antennas.
