Here's a relevant article from the Washington Post that explains more.

   Z-104 Silenced; Post Radio To Debut in Station Shuffle

   Washington Post
   January 5, 2006
   http://www.washingtonpost.com/wp-dyn/content/article/2006/01/04/AR2006010400849_pf.html

   Radio broadcaster Bonneville International Corp. shook up
   Washington's airwaves yesterday by moving its all-news station
   WTOP and classical outlet WGMS-FM to new frequencies, eliminating
   pop music station Z-104 and announcing plans for a news-and-talk
   station it will program with The Washington Post.

   The moves involve three local stations that occupy six slices
   of the AM and FM bands.  By reshuffling its station lineup,
   Bonneville is attempting to place its most popular and lucrative
   programming -- news -- on the frequencies that have the strongest
   broadcast signals.  At the same time, it essentially is backing
   out of the music field, eliminating airplay of contemporary
   recordings and consigning classical to one of its weakest signals.

   With only a perfunctory on-air announcement, the Utah-based
   broadcasting giant at noon yesterday triggered the local radio
   version of musical chairs.  It abruptly knocked WGMS off of 103.5
   FM and moved WTOP into that slot.  WGMS, in turn, moved to 104.1
   and 103.9 -- the former homes of the pop station Z-104, which
   immediately disappeared.  In a flash Z-104's listeners went from
   hearing upbeat deejays and adult-contemporary singles to a
   dulcet-toned announcer introducing a Rachmaninoff piano concerto.

   On March 30, two of WTOP's frequencies (1500 AM and 107.7 FM)
   will switch to Washington Post Radio, news and talk programming
   that Bonneville will produce with The Post, which owned WTOP
   from 1949 to 1978. Bonneville will continue to own the stations
   under a new trademark and content-licensing agreement.   ...

   Classical music fans, particularly in the District and Montgomery
   County, will find it harder to get a clear signal for WGMS at
   its new frequencies. The station's broadcast towers are in Waldorf
   and Frederick, and the potential for interference or lost signals
   could drive away some listeners, an executive at a rival radio
   company said yesterday.

   Yesterday's announcements underscored the changing nature -- and
   to some extent, the slow shrinking -- of radio as a music medium.
   Although radio airs many kinds of music, direct competition among
   genres is rare. Washington, for example, was left with only one
   contemporary rock station (DC101, WWDC-FM) after WHFS-FM switched
   to a Spanish-language pop music format last January, and with
   one major classical station (WGMS) after WETA-FM switched to
   news and talk in March.  ...

   According to BIA, Z-104 had revenue of $9.9 million in 2004,
   slightly more than WGMS's $9.3 million.  But company analyst
   Mark Fratrik estimated that WGMS was more profitable because of
   the lower cost of operating a classical station compared with a
   pop station, which requires heavy promotion and relatively highly
   paid deejays.  ...

 - seb