Here is a diagram of the CSM Unified S-Band Antenna, taken from the Apollo Experience Report: S-Band System Signal Design and Analysis. Page 10 (p. 18 in the PDF) describes the antenna: "The high-gain antenna consists of an 11-inch-diagonal wide-beam horn flanked by an array of four 31-inch-diameter parabolic reflectors."

Stafford Air & Space displays a high gain antenna.

Click image for a 878x1548 pixel version of this image in a new window.
From p. 10 (p. 18 in the PDF) of Apollo Experience Report: S-Band System Signal Design and Analysis
Extraction and cleanup by heroicrelics.