Fox launched in 1986 as Fox Broadcasting Company. It used a logo that had 3 squares with the channel's initials, similar to the current logo of the BBC. Underneath was a rectangle with the channel's full name in the same font.
Later in 1986, Fox Broadcasting Company changed to just Fox, launching with a logo that slightly resembled the 20th Century Fox print logo. A negative space makes the O.
In 1987, Fox changed their logo to make it look more like the 20th Century Fox print logo.
In 1993, Fox changed their logo to a front-facing version of the previous logo.
The Fox text was made smaller in this version, and the searchlights were moved closer to the edge of the rectangle.
The black rectangle and searchlights were removed in this version, and a bar was added at the top.
In 1996, the 1994 logo returned, this time without the two black bars at the bottom. Also, the searchlights were made thicker and longer. Although it's no longer used as of 1999, it still remains in use on plenty of Fox affiliates' logos. It also appears on the alternate logo of Fox News Channel mainly for the cable network's special breaking news reports and news productions as seen on the Fox television network.
In 1999, the logo was reduced to just the Fox text.