My understanding is that the value of the axis (like -10 / 0 dB) refers to the maximum antenna gain (e.g. 12dbi).

So, if a point on the figure is -5dB, then antenna gain of that point is

12 - 5 = 7 dBi.

Is this correct?

The axes in the figure are in degrees and dB.



In your example, the outer ring in the polar plot would be 12 dBi. So you are correct in thinking that any point -5 dB from the outer ring would represent a gain of 7 dBi.

It works the same for referencing dB, dBi (isotropic), and dBd (dipole).

  • $\begingroup$ More detailed information about pattern plots can be found here. $\endgroup$
    – Mike Waters
    Jul 22 '19 at 19:45
  • $\begingroup$ Also, since Mike mentions dBi and dBd, remember that 0dBd = 2.15dBi. So if you see one, and need to convert to the other, that's all you need to note. $\endgroup$
    – Scott Earle
    Jul 23 '19 at 6:59
  • $\begingroup$ Thank you so much !! haha !! first time I did not notice the db in the figure $\endgroup$
    – vvv
    Jul 26 '19 at 5:21

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