Ok I screwed up by referring to the Sommer antenna site for Capture Area

But I was taught that antenna gain is a function of Aperture - part of the
classic radar range equation
https://ewhdbks.mugu.navy.mil/2waymon.htm

For Aperture discussion see URL:
https://ewhdbks.mugu.navy.mil/ANTENNAS.HTM

So would be interested in your comments on Antenna aperture and antenna gain
and capture area

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CL -- I doubt, therefore I might be !