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Environmental Impact of W ind Projects 263

validating the exact locations and height of microwave antennas by
contacting the licensee. The reason is that FCC database may not have
precise locations and heights of microwave transmitters or receivers
either because of measurement error or because the installation was
updated without informing the FCC. In case microwave interference
is found, then the turbine must be relocated.

T V and Radio Transmissions
Similar to microwave signal, TV signal are susceptible to interfer-
ence. Here, in addition to direct obstruction of the line-of-sight be-
tween transmitter and receiver, a second mechanism causes signal
interference. This mechanism is scattering of signal, which causes the
receiver to get two signals: Direct signal and scattered signal that is
delayed, which impact the picture quality by producing ghost images.
Sound quality is typically not affected. TV reception can normally be
fixed with improvements to antennas and changes to setup of the
antenna.

Radar
Wind turbines interfere with radars installed for the purpose of moni-
toring weather, and detecting and tracking incoming aircraft and mis-
siles. In the United States, radar operators include National Weather
Service, Department of Defense, Homeland Security, FAA, and oth-
ers. Rotation of wind turbine blades can create clutter interference and
Doppler interference with radar signals. Examples of impact of wind
farms on radar include:

1. In the United States, the National Weather Service (NWS) has
159 Next Generation Weather Radar (NEXRAD). When wind
farms are located in the radar line of sight (RLOS) then there
are three types of impact: 11
Wind turbines reflect energy whose signal can be confused

with a storm. This contaminated reflectivity data is called
clutter.
If turbines are within a few kilometers, then the turbine

can block a significant portion of the radar signal that can
cause the radar to not “see” events behind the wind farm.
Figure 12-3 is a chart of impact from the NWS.
The velocity and spectrum width data can be impacted,

which may result in issues with algorithms to detect certain
storm characteristics, such as tornadoes, storm motion, and
turbulence.
2. As shown in Fig. 12-3, the impact is the greatest when the
turbine is within a few kilometers. According to Vogt et al., 11
turbines within 200 m of radar are not safe; turbines within