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@Fred's comment links to the Australian Broadcasting Corporation's How the Apollo 11 Moon landing was achieved with the vital help of Carnarvon Tracking Station which links to their Carnarvon space tracking station report. I show two screen shots below from a video in both links, of a large, flat, square tracking antenna made from an 6x6 array of overlapping circular patterns.

What antenna is this, and how does it work?

enter image description here

enter image description here

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    $\begingroup$ It looks like a common-mode antenna with dipoles in vertical and horizontal polarization. In the USSR for space television an antenna was used in the form of an in-phase array of 384 helical emitters kik-sssr.ru/VNIIT_Krechet-Fobos/i0002rp.jpg $\endgroup$ – A. Rumlin Jan 19 at 8:48
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This type of antenna is known as a phased array, typically a group of similar smaller antennas arranged side by side. The electrical signal feed to the array includes delay elements and sometimes attenuation elements to "weight" the signal fed to or from the antenna elements that combine to form a narrow beam. Modern phased arrays are often used in RADAR or satcom antennas to allow fast electronic steering of the beam simply by changing the weights applied to the various elements. See: https://en.wikipedia.org/wiki/Phased_array

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  • $\begingroup$ This is of course true as far as this goes, but a phased array of what? What is the 6x6 pattern of overlapping circles? What kinds of radiators are used? How does it work? Thanks! $\endgroup$ – uhoh Jan 20 at 18:40
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    $\begingroup$ While the antenna elements initially looked like turnstiles, I am wondering about the structure behind the mesh surface. It's possible the elements are some kind of cavity-backed dipole, the cavity being the oval shaped thing beneath the mesh. Possibly done this way to reduce coupling between the elements. $\endgroup$ – Judd Jan 20 at 19:04

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