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Enterprise Park to Crooked Lake 115 kV Transmission Line March 2012 Environmental Assessment Interference also depends on the weather conditions. In humid conditions, corona is higher than it would be in dry weather. Under ideal conditions, the conductor cables would be free of corona discharges; protrusions, such as water droplets on the cable, enhance the electric field in the vicinity of the droplet to a size where corona could become present (Straumann and Fan, 2009). AM radio reception (in broadcast bands 535 to 1605 kilohertz (kHz)) interference typically is stronger if a radio unit and/or antenna is located beneath the transmission line and dissipates rapidly within the ROW to either side of the transmission line. Modifying a radio antenna and/or relocating a radio unit (i.e., away from a transmission line and away from a metallic tower -type structure) are simple ways to restore AM reception on a device that originally had good reception prior to the interference. FM radio reception is rarely affected by the presence of transmission lines. Since corona generated radio frequency noise currents decrease in magnitude as frequency increases, the effects of corona are quite small in a FM broadcast band (88-108 Megahertz). In addition, FM radio systems have inherent excellent interference rejection properties. Television signals are rarely affected by corona interference. However, some interference may be possible, if a shadow effect is created when a large transmission structure is aligned between a receiver and a weak signal. Digital signals are more tolerant of electric interference. Interference with television reception can be corrected by several methods including adjusting the television antenna, installing a remote antenna, and installing a translator. GPS collects and coordinates data from at least four satellites at any one time. As such, constellation, positioning of the four satellites, and signal strength are the most important factors that decide accuracy of the GPS. In 2002, the Institute of Electronics and Electrical Engineers (IEEE) conducted a series of experiments to observe if overhead transmission lines interfere with the GPS function. One of the tests utilized a Trimble GPS receiver near a 345 kV line to determine if corona noise and gap discharge could affect the "lock" a receiver had on the satellite constellation above. The results from this experiment by IEEE are as follows: • Generally, GPS function is very minimally affected by transmission line electromagnetic interference (EMI). • Interference that is caused could be either due to corona noise or gap discharges. • Rarely, transmission structure may cause a drop in accuracy due to blocking a view of at least one of the satellites from GPS. However, corona noise and gap discharges do not cause loss of a satellite signal "lock" (IEEE, 2002 as cited in Minnkota Power Cooperative, Inc., n.d.). Based on this research, GPS signals very rarely experience interference from overhead transmission lines. On rare occasions, a transmission line structure may cause a drop in accuracy within a GPS device due to blocking a view to one satellite, but this would only occur if the receiver, tower, and satellite are in a line, which is rare. Typically, if there is 30