Siemens SIMATIC RF640A Operating Instructions Manual page 28

Polarization axis and axis of symmetry are orthogonal to each other
In the following directional radiation pattern of the antenna, the axis of symmetry of the antenna and the polarization axis of
the transponder are orthogonal to each other.
Pattern of the vertical plane of the antenna
Pattern of the horizontal plane of the antenna
Figure 7 The RF640A directional radiation pattern in the FCC frequency band, axis of symmetry of the antenna, and
polarization axis of the transponder are orthogonal to each other
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SIMATIC RF640A
J31069-D0225-U001-A2-7618, 12/2010