When comparing dish antennas of the same frequency, larger-sized antennas are generally more efficient at focusing the signal and result in a higher antenna gain. The gain of a dish antenna is influenced by its size relative to the wavelength of the signal it is designed to receive or transmit.
Here's why larger dish antennas typically provide higher gain:
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Aperture Efficiency: Larger antennas have a larger effective aperture, which allows them to collect more of the electromagnetic waves coming towards them. This increased collection area leads to better signal focus and higher gain.
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Narrower Beamwidth: Larger antennas can produce a narrower beamwidth. A narrower beamwidth means that the antenna can more effectively concentrate the signal in a specific direction, enhancing directivity and gain.
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Reduction of Side Lobes: Larger antennas tend to have better side lobe performance, which means they are less likely to pick up unwanted signals from nearby directions. This results in a cleaner signal and better overall performance.
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Higher Directivity: The larger surface area allows for greater directivity, meaning the antenna can better discriminate between signals coming from different directions, which contributes to increased gain.
In summary, for antenna applications where focusing the signal is critical, larger dish antennas are generally preferred due to their higher gain capabilities resulting from their ability to collect more signal and provide better directionality.