Science Fair Projects Ideas - Clear channel

All Science Fair Projects

 		      

Science Fair Project Encyclopedia for Schools!
  Search    Browse    Forum  Coach    Links    Editor    Help    Tell-a-Friend    Encyclopedia    Dictionary     

Science Fair Project Encyclopedia

For information on any area of science that interests you,
enter a keyword (eg. scientific method, molecule, cloud, carbohydrate etc.).
Or else, you can start by choosing any of the categories below.

Science Fair Project Encyclopedia Contents Page

Clear channel

For information on the company named Clear Channel, see Clear Channel Communications.

Clear channel stations are AM radio stations that are designated as such so that only one or two 50,000 watt powerhouses operate at night on each designated frequency, covering a wide area at night via sky wave propagation. Non-clear channel stations transmitting on these frequencies are (or were) required to shut down at night, leading them to be known as daytimers. In North America, some frequencies were designated by the North American Radio Broadcasting Agreement (NARBA) (to which the U.S., Canada, and Mexico are signatory) as clear channels. These are considered by the FCC and CRTC to be class A (formerly class 1-A or I-A) stations. Daytimers are in class D.

For the U.S., clear channels first appeared in 1922 when the Commerce Department moved stations which had all used two frequencies (one for entertainment stations, one for news) onto 52 frequencies. Two were used for all low-power stations and the large stations each got their own frequency. A few frequencies were used on both the East and West Coast, which were considered far enough apart to limit interference. At this time large stations were limited to 1000 watts. Later in 1928, the AM band was reorganized with local, regional and clear channels (and a few reserved for Canada) by the new Federal Radio Commission. Gradually maximum power was increased to 50,000 W. This system was continued in the 1941 NARBA system although almost all stations shifted broadcast frequencies.

Recently however, the FCC has authorized nighttime operation by lower-powered stations on these frequencies, thus limiting the non-interference range of the primary licensees. Stations are still required to reduce power or reconfigure their transmitters at night. Regional class stations have been allowed to increase their power to the same 50,000 W as clear channel stations. In 1987 the rules were changed so that no new stations would have daytime-only licenses.

This article is not related to Clear Channel Communications, a San Antonio, Texas-based company that owns a large number of U.S. radio stations, though they did take their name from the term.

Clear channels in North America

Stations are listed by frequency in kilohertz (kHz), then by callsign. Stations noted beside frequency are the ones designated under NARBA as clear channels (class A stations).

External links

Science Fair Project Encyclopedia Contents Page
03-10-2013 05:06:04
The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details
Science kits, science lessons, science toys, maths toys, hobby kits, science games and books - these are some of many products that can help give your kid an edge in their science fair projects, and develop a tremendous interest in the study of science. When shopping for a science kit or other supplies, make sure that you carefully review the features and quality of the products. Compare prices by going to several online stores. Read product reviews online or refer to magazines.

Start by looking for your science kit review or science toy review. Compare prices but remember, Price $ is not everything. Quality does matter.
Science Fair Coach
What do science fair judges look out for?
ScienceHound
Science Fair Projects for students of all ages
All Science Fair Projects.com Site
All Science Fair Projects Homepage
Search | Browse | Links | From-our-Editor | Books | Help | Contact | Privacy | Disclaimer | Copyright Notice