Thierry wrote:
Up to now the U. S. Federal Communications Commission oversees the
operations of U.S. private sector international broadcasters, and
assigns 4 character alphabetic call signs to the international broadcasters.
But what about a company like VOA's (Voice of America) and thousands
others who use a trade name instead of a callsign ?
Aren't they under the FCC authority ?

No, stations that belong to the U.S. federal government are NOT under
FCC authority. The FCC only regulates private use of radio, and use by
state and local (city, county, etc.) governments. Most federal
government stations do not have callsigns.

The Armed Forces Radio and Television Service (AFRTS) is another U.S.
government-operated broadcast service that doesn't have callsigns. Of
course most AFRTS stations are located outside U.S. territory, but the
few that are U.S. based (especially in Puerto Rico and Alaska) do not
have calls.

(the most prominent exception: the USA National Weather Service operates
a nationwide chain of weather broadcasting stations between 162.4 and
162.55MHz. All of them have callsigns, even though almost all of them
belong to the Weather Service, a federal agency.)

--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com