Siemens SIMATIC RF600 Series System Manual page 306

Antennas
6.7 SIMATIC RF660A
USA (FCC)
The radiation diagram is shown for horizontal alignment and for a center frequency of 915
MHz.
The radiating/receiving angle of the antenna is defined by the angle between the two -3 dB
points (corresponding to half the power referred to the maximum performance at a 0° angle).
The optimum radiating/receiving angle is therefore approximately ±35 degrees.
Figure 6-50 Directional radiation pattern of the antenna (at 915 MHz, horizontal alignment)
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System Manual, 11/2018, J31069-D0171-U001-A21-7618
SIMATIC RF600