Editing Reginald Fessenden (section)

===Weather Bureau contract===
[[File:Cobb island md aerial.jpg|thumb|[[Cobb Island, Maryland|Cobb Island]] on the [[Potomac River]], scene of the first successful radio transmission of speech in the fall of 1900.]]
In 1900 Fessenden left Pittsburgh to work for the [[United States Weather Bureau]], with the objective of demonstrating the practicality of using coastal stations to transmit weather information, thereby avoiding the expense of the existing telegraph lines. The contract called for him to be paid $3,000 per year and provided with work space, assistance, and housing.<ref name="Karwatka, D. 2004">Karwatka, D. (2004). "Reginald Fessenden and Radio Transmission". ''Tech Directions'', March 2004, 63(8), 12.</ref> Fessenden would retain ownership of any inventions, but the agreement also gave the Weather Bureau royalty-free use of any discoveries made during the term of the contract. Fessenden quickly made major advances, especially in receiver design, as he worked to develop audio reception of signals. His initial success came from the invention of a [[barretter detector]]. This was followed by an [[electrolytic detector]], consisting of a fine wire dipped in nitric acid, which for the next few years set the standard for sensitivity in radio reception.<ref>[https://babel.hathitrust.org/cgi/pt?id=uc2.ark:/13960/t4pk08c44&view=1up&seq=142 "Electrolytic Detectors"], ''Wireless Telegraph Construction For Amateurs'' by Alfred Powell Morgan, 1914, p. 118.</ref>

As his work progressed, Fessenden also developed the [[heterodyne principle]], which used two closely spaced radio signals to produce an audible tone that made [[Morse code]] transmissions much easier to hear. However, heterodyne reception would not become practical for a decade after it was invented, because it required a method for producing a stable local signal, which would not become available until the development of the oscillating [[vacuum-tube]].<ref>Aitken (1985) pp. 58–60.</ref>

Fessenden's initial Weather Bureau work took place at [[Cobb Island (Maryland)|Cobb Island]], Maryland, located in the [[Potomac River]] about {{convert|80|km|mi|sp=us}} downstream from Washington, D.C. As the experimentation expanded, additional stations were built along the Atlantic Coast in North Carolina and Virginia. However, in the midst of promising advances, Fessenden became embroiled in disputes with his sponsor. In particular, he charged that Bureau Chief Willis Moore had attempted to gain a half-share of the patents. Fessenden refused to sign over the rights, and his work for the Weather Bureau ended in August 1902.<ref>This incident recalled [[Francis Ormand Jonathan Smith|F. O. J. Smith]], a member of the House of Representatives from Maine, who had used his influence to gain a one-quarter interest in [[Samuel Morse]]'s telegraph.</ref>