https://www.rfwireless-world.com/calculators/conical-horn-antenna-gain-calculator-and-formula
Conical Horn Antenna Gain Calculator | RF Aperture | RF Wireless World
Quickly calculate the gain of a conical horn antenna. Input aperture diameter and frequency for accurate dBi gain results.
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https://financialtoolset.com/tools/rf/parabolic-antenna-calculator/
Parabolic Antenna Gain Calculator | RF Tools
Calculate parabolic dish antenna gain, beamwidth, and effective area for satellite and microwave links.
antenna gain calculatorrftools