Siemens SIMATIC RF600 System Manual page 192

Transponder/tags
7.3 SIMATIC RF620T
If the transponder is positioned orthogonally to the transmitting antenna, it normally cannot
be read. Therefore the data carrier is preferably to be aligned parallel to the transmitting
antenna. The following figure illustrates this situation.
Figure 7-11 Application example for possible orientations of the transponder.
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System Manual, 10/2009, J31069-D0171-U001-A8-7618
SIMATIC RF600