Editing Direction finding (section)

===Emergency aid===

[[Emergency position-indicating rescue beacon]]s are widely deployed on civil [[aircraft]] and ships. Historically emergency location transmitters only sent a tone signal and relied on direction finding by search aircraft to locate the beacon. Modern emergency beacons transmit a unique identification signal that can include [[GPS]] location data that can aid in finding the exact location of the transmitter.

[[Avalanche transceiver]]s operate on a standard 457&nbsp;kHz, and are designed to help locate people and equipment buried by avalanches. Since the power of the beacon is so low the directionality of the radio signal is dominated by small scale field effects<ref>*{{cite journal
 |author1       = J. Hereford
 |author2       = B. Edgerly
 |name-list-style = amp
 |year          = 2000
 |title         = 457 kHz Electromagnetism and the Future of Avalanche Transceivers
 |journal       = International Snow Science Workshop (ISSW 2000)
 |url           = http://www.backcountryaccess.com/images/documents/457andFuture_000.pdf
 
 |url-status       = dead
 |archive-url    = https://web.archive.org/web/20110722082049/http://www.backcountryaccess.com/images/documents/457andFuture_000.pdf
 |archive-date   = July 22, 2011
}}</ref> and can be quite complicated to locate.