Radio-Locator Home Page
find US radio stations by location
city/zip state
find by callsignsite navigation

Radio-Locator Help Page

Critical Hours

The two hours immediately after sunrise and the two hours directly before sunset are referred to as "Critical Hours".

AM radio signals travel farther at night due to ionization of the Earth's atmosphere. To prevent interference with other stations far away, many AM stations have to either sign off the air, reduce their transmitter power, or change their antenna patterns at night. Some AM radio stations also have to change their power or antenna patterns during these "Critical Hours" because of changes in the atmosphere at those times as well.


radio station email addresses & mailing lists
© 2018 Theodric Technologies LLC.