Orono_Route_Permit_Application - Docket # W002/TL-11-223

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6.2.5 Television and Radio Interference Corona from transmission line conductors can generate electromagnetic "noise" at the same frequencies that radio and television signals are transmitted. This noise can cause interference with the reception of these signals depending on the frequency and strength of the radio and television signal. Tightening loose hardware on the transmission line usually resolves the problem. If radio interference from transmission line corona does occur, satisfactory reception from AM radio stations presently providing good reception can be obtained by appropriately modifying (or adding to) the receiving antenna system. Moreover, AM radio frequency interference typically occurs immediately under a transmission line and dissipates rapidly within the right-of-way to either side. FM radio receivers do not usually pick up interference from transmission lines because: • corona -generated radio frequency noise currents decrease in magnitude as the frequency increases and are quite small in the FM broadcast band (88-108 Megahertz); and • the excellent interference rejection properties inherent in FM radio systems make them virtually immune to amplitude -type disturbances. A two-way mobile radio located immediately adjacent to and behind a large metallic structure (such as a steel tower) may experience interference. Moving either mobile radio so that the metallic structure is not immediately between the two units should restore communications. This will generally require a movement of less than 50 feet by the mobile radio adjacent to the metallic tower. Television interference is rare but may occur when a large transmission structure is aligned between the receiver and a weak distant signal, creating a shadow effect. Loose or damaged transmission line hardware may also cause television interference. Digital reception is, in most cases, considerably more tolerant of electric interference and somewhat less resistant to multipath reflections. In the digital realm, the picture does not gradually degrade; rather, at what is called the "avalanche point," the picture suddenly pixelates (turns into squares) and usually "freezes." Mitigative Measures No impacts are anticipated from the proposed Project. However, if radio or television interference occurs because of the transmission line, Xcel Energy will work with the affected parties to restore reception to pre -Project quality. If the interference is due to the power line, the electric utility will remedy problems so that reception is restored to its original quality. Generally, the problem is resolved by moving or raising or adjusting the customer's antenna. In some instances, a more effective antenna or a signal amplifier is required. 6.2.6 Aesthetics The proposed substation replacement will be within existing Xcel Energy property and the transmission facilities will mainly follow existing BNSF railroad and U.S. Highway 12 rights-of-way. The Project will have some effects on the visual and aesthetic character of the area. Orono Project June 7, 2011 MPUC Docket No. E002/TL-11-223 45