This calculator is designed to help you create a quarter wave ground plane antenna with radials. The main radiating element is a quarter wavelength (λ/4), while the radials are 12% longer. Typically, four radials are used, though three is the minimum, and up to six can be implemented. This antenna is truly unbalanced, with a feed impedance of approximately 50Ω, making it a perfect match for a 50Ω unbalanced feedline. The velocity factor is set at 95%, which should work well for most applications. If you have the proper tools, you can cut the antenna slightly larger and trim it to achieve the best match at your target frequency.
Building these antennas for UHF or higher frequencies is simple, requiring a chassis-mount N-Type (or SO-239) connector, solid wire, and solder. For VHF and lower frequencies, as the elements grow in size, a more structured design approach is necessary.
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