||This article includes a list of references, related reading or
external links, but its sources remain unclear because it lacks
inline citations. (April 2013)| The service area from a
television (TV) or frequency modulated (FM) radio transmitter
extends to just beyond the optical horizon, at which point
signals start to rapidly reduce in strength. Viewers living in
such a "deep fringe" reception area will notice that during
certain conditions, weak signals normally masked by noise
increase in signal strength to allow quality reception. Such
conditions are related to the current state of the troposphere.
Tropospheric propagated signals travel in the part of the
atmosphere adjacent to the surface and extending to some 25,000
feet (7,620 m). Such signals are thus directly affected by
weather conditions extending over some hundreds of miles. During
very settled, warm anticyclonic weather (i.e., high pressure),
usually weak signals from distant transmitters improve in
strength. Another symptom during such conditi