WWX-AM was unlike all other experimental AMs. It and WWQ in Bellafonte Pennsylvania were a part of Air Mail Radio (AMR) and were the predecessors of modern Flight service stations. It wasn't until September of 1919 that The post office commissioned facilities for the stations. How they operated (and who) for the 5 interim years I do not know. By 1920 the Post office was operating a transcontinental service and was actively building airmail radio stations to support this service. By 1921 they had commissioned seventeen stations, one at each of the airfields they used. [Note the history of WWQ is even more murky since it's calls were also used by a US merchant ship at the same time!]
great history here.
Despite their progress the Airmail act of 1925 was passed and with it government operation of airmail came to an end. [On the plus side Fed Ex and UPS came to begin] On August 12, 1918, the Post Office Department took over airmail service from the U.S. Army Air Service (USAAS). Assistant Postmaster General Otto Praeger appointed Benjamin B. Lipsner, who left the USAAS, to head the civilian-operated Air Mail Service. One of Lipsner's first acts was to hire four pilots, each with at least 1,000 hours flying experience, paying them an average of $4,000 per year. The department also abandoned the polo grounds in Washington, D.C., and moved north to the larger airfield at College Park, Maryland, where it would begin its route to Philadelphia. was moved out of the post office's Monmouth facility and into The Aeronautical Office and their College park airstrip. http://www.pgparks.com/places/historic/cpam/3radio.html
In 1919 the U.S. Commerce Department formally established a broadcast service, with 833 KHz set aside for entertainment broadcasts, and 619 KHz designated for official government market and weather reports. In the Washington D.C. area only WIAY and WQAW received an authorization for 833 KHz. The first broadcast station licensed in the Washington area was WJH-AM on December 8, 1921. Fourteen days later WDM-AM and WDW-AM, received licences tying for 25th place nationwide.
Some stations survived and prospered and in fact are here today. Other became deleted. Of the above stations WJH was deleted in 1924, WDM was deleted in 1925, WDW was deleted in 1922, WQAW and WIAY were both off air by th end of 1924.
While all these stations were going off air the Navy started a second experimental station, 690 NAA in Arlington. It was built as a radiotelegraph station in 1913, right after NOF and WWX, and was located next to Fort Myer in Arlington, VA. In the mid-twenties NAA started to transmit on the broadcast band. Although its broadcasts occasionally included band concerts and speeches, it was mostly used for time signals. By 1927 it was one of three stations on air in that city. The other two were WRC on 640AM and WMAL, then on 1410. Everything else was gone. It wasn't until the early 1940's that radio recovered in D.C.
As typical, much of my D.C. radio history comes from Dave at http://www.dcrtv.org