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I have purchased a circularly polarized antenna with a gain of 2.54dBi at 1W. If you require additional specs please let me know. My question is does the gain of the antenna equals the multiply of the power, for instance, if the input power is 4W then the gain is 4x2.54=10.16dBi?

Or does it still remain at 2.54dBi at 4W?

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  • \$\begingroup\$ It either stays the same, or even falls to a lower value if the antenna's rated power is less than 4W. (Which may be true for the sort of chip antenna used in phones) \$\endgroup\$
    – user16324
    Commented Mar 1, 2020 at 15:04

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An antenna gain of 2.54dBi means it has 2.54dB greater launch power in its maximum direction than does an isotropic antenna. That's what the 'i' in dBi means, taking as a reference the isotropic antenna.

A physical isotropic antenna doesn't exist, it's what you get if you theoretically spread all your input power evenly over the full \$4\pi\$ steradians around it. Thus even a simple dipole has a gain of about +3dBi in its maximum directions.

If the input power is 1 watt, then it outputs +2.54dBW/\$4\pi\$ per steradian in its maximum direction. If the input power is 4 watts, it outputs +8.56dBW/\$4\pi\$ steradian. An increase of 4x in power is an increase of 6.02dB

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  • \$\begingroup\$ The dipole only has a gain of 3 dBi in the directions of its two main lobes; it has a loss in the longitudinal direction.. \$\endgroup\$
    – Chu
    Commented Mar 2, 2020 at 1:09
  • \$\begingroup\$ @Chu Two main lobes? The dipole has a single doughnut-shaped main lobe, which looks like two if you take a slice through it. \$\endgroup\$
    – Neil_UK
    Commented Mar 2, 2020 at 4:34

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