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Local Sunrise / Sunset Calculations

Given a set of coordinates (latitude and longitude) in degrees / minutes / seconds, this program will calculate the approximate average monthly sunrise and sunset times at that location. These values are important to those AM stations who must reduce power, cease operations, or change to directional operation during the nighttime hours, as well as the stations protected by the changed operation. (See Why AM Radio Stations Must Reduce Power, Change Operations, or Cease Operations at Night for more explanation.) The coordinates (latitude and longitude) for a specific AM station may be retrieved from the AM Query.

In the program below, you may select the U.S. time zone in which you are interested. For example, a listener may want to know when a particular daytime-only AM station in the next time zone will cease operation for the night. That person would enter the coordinates of the station, his time zone, into this program and receive the answer.

AM licensees should be aware that local sunrise / sunset times specified on AM radio station authorizations issued by the FCC will be made using STANDARD time (NOT advanced or daylight savings time). This program, however, will allow computations with advanced or Daylight Savings Time (1 hour ahead of Standard Time). This program does not have sufficient data to calculate local times for latitudes above 60° North Latitude (i.e., northern Alaska or Canada), or east of 63° West Longitude, or at any locations for South Latitude or East Longitude.

Many AM broadcast radio stations operate with presunrise authority (PSRA) or postsunset authority (PSSA). These special authorizations allow the station to incrementally change power or mode of operation before sunrise or after sunset, in recognition that changes in the ionosphere (the atmospheric layer that reflects AM signals at night) do not occur instantly at nightfall or at sunrise. For these stations, the times shown by this program will generally indicate when the incremental station changes must begin.





     


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