  Modern radio astronomical facilities are able to detect extremely weak
electromagnetic signals not only from the universe but also from man-made radio
frequency interference of various origins. These range from wanted signals to
unwanted out-of-band emission of radio services and applications to
electromagnetic interference produced by all kinds of electronic and electric
devices. Energy harvesting wind turbines are not only equipped with electric
power conversion hardware but also copious amounts of electronics to control
and monitor the turbines. A wind turbine in the vicinity of a radio telescope
could therefore lead to harmful interference, corrupting the measured
astronomical data. Many observatories seek to coordinate placement of new wind
farms with wind turbine manufacturers and operators, as well as with the local
planning authorities, to avoid such a situation. In our study, we provide
examples as well as guidelines for the determination of the separation
distances between wind turbines and radio observatories, to enable a benign
co-existence for both.
  The proposed calculations entail three basic steps. At first, the anticipated
maximum emitted power level based on the European EN 550011 (CISPR-11)
standard, which applies to industrial devices, is determined. Then secondly,
the propagation loss along the path to the radio receiver is computed via a
model provided by the international telecommunication union. Finally, the
received power is compared to the permitted power limit that pertains in the
protected radio astronomical observing band under consideration. This procedure
may be carried out for each location around a telescope site, in order to
obtain a map of potentially problematic wind turbine positions.
