Радиотихая зона в США: Ограничения на радиосвязь для научных исследований.

Specific land area in which radio transmissions are heavily restricted

The National Radio Quiet Zone (NRQZ) is a large area of land in the United States designated as a radio quiet zone, in which radio transmissions are restricted by law to facilitate scientific research and the gathering of military intelligence. About half of the zone is located in the Blue Ridge Mountains of west central Virginia while the other half is in the Allegheny Mountains of east central West Virginia; a small part of the zone is in the southernmost tip of the Maryland panhandle.

The Quiet Zone is an approximate rectangle of land, 107.0 mile (172 km) on the north edge, 109.6 mile (176 km) on the south edge and 120.9 mile (195 km) on the east and west edges, comprising approximately 13000 square miles (33,670 km2). It straddles the borders of Virginia and West Virginia, and also includes a small part of Maryland. The NRQZ is centered between the Green Bank Observatory in Green Bank, West Virginia, and Sugar Grove Station in Sugar Grove, West Virginia. It includes all land with latitudes between 37° 30′ 0.4″ N and 39° 15′ 0.4″ N, and longitudes between 78° 29′ 59.0″ W and 80° 29′ 59.2″ W.

Most broadcast transmitters in the central area of the Quiet Zone are required to operate at reduced power and use directional antennas. This makes cable and satellite all but essential for acceptable television in much of the region. Restrictions of transmissions are strictest within ten miles (16 km) of the Green Bank and Sugar Grove facilities, The Observatory polices the area actively for devices emitting excessive electromagnetic radiation such as microwave ovens, Wi Fi access points and faulty electrical equipment and request citizens discontinue their usage. It does not have enforcement power (although the FCC can impose a fine of $50 on violators), but will work with residents to find solutions. Cellular telephone use in the central area of the zone is also very restricted.

The Green Bank Interference Protection Group maintains policies to manage radio frequency interference (RFI) by dividing into five zones based on available legal instruments. Zone 1 and Zone 2 are located within the property of the Green Bank Observatory. The entire property is designed as Zone 1 except small portions (such as housing, visitor, and laboratory areas) that are designed as Zone 2. Zone 1, also termed the Radio Astronomy Instrument Zone, restricts intentional radiators only to those are deemed essential. All unintentional radiators must be operated within the ITU R RA.769 recommendations on protection criteria used for radio astronomical measurements. Gasoline powered motor vehicles are prohibited in Zone 1 as their spark ignition engines generate significant radio interference, resulting in the requirement that all vehicles and equipment be diesel powered. Zone 2, also called Observatory Building Zone, allows intentional radiators licensed by National Radio Quiet Zone, but not other radiators such as Wi Fi, cordless phones, and other wireless equipment. Certain types of unintentional radiators are allowed. Digital cameras are prohibited, although film photography is allowed. Zone 3 and Zone 4 are governed by the Radio Astronomy Zoning Act which is the Chapter 37A of the West Virginia Code. It strictly regulates radio transmitters within 2 mile (3 km) and within 10 mile (16 km) of the Green Bank Observatory, respectively. Within these zones, interference to observations will be identified and documented. The owners of the offending equipment will be visited personally to request cooperation in eliminating the interference. Enforcement is used as a last resort. Enforcement in Zone 4 may be more lenient than the limit set by Chapter 37A. Zone 5 is the boundary of National Radio Quiet Zone; the National Radio Quiet Zone Administrator at the Green Bank Observatory manages the enforcement policies.