Siemens SIMATIC RF 300 System Manual page 33

Mounting of several readers on metal frames or racks
Any reader mounted on metal couples part of the field to the metal frame. There is normally
no interaction as long as the minimum distance D and metal-free areas a, b are maintained.
However, interaction may take place if an iron frame is positioned unfavorably. Longer data
transfer times or sporadic error messages at the communication module are the result.
Mounting of several readers on metal racks
RF 300
System Manual, 05/2005, (4)J31069 D0166-U001-A1-7618, --
Problem: Interaction between readers
Remedy
Increase the distance D between the two readers.
Remedy
Introduce one or more iron struts in order to short-
circuit the stray fields.
Remedy
Insert a non-metallic spacer of 20 to 40 millimeter
thickness between the reader and the iron frame. This
will significantly reduce the induction of stray fields on
the rack:
RF 300 system planning
4.4 Installation guidelines
4-17