Reginald A. Fessenden House
Reginald A. Fessenden was born Quebec in 1866, and entered Bishop's University as a precocious young mathematical prodigy, but left in 1884 without graduating. In 1886, he took a position at the Edison Machine Works, working for inventor Thomas Edison. During an academic period teaching at Purdue University and at the University of Pittsburgh, Fessenden engaged in research on the nascent subject of wireless telegraphy. Much of the rest of his life he was employed in industry, either directly or as a consultant, but was often living near poverty, and produced a stream of inventions. In 1904 he invented the rotary spark-gap transmitter, and in 1906 he built a large transmitter in Massachusetts from which he successfully made a voice transmission. He also discovered the means to recombine separate frequencies to form a coherent audible sound. At his death he was described by inventor and businessman Elihu Thomson as "the greatest wireless inventor of the age, greater than Marconi."
Radio receiver
In 1901 Reginald Fessenden had invented a better means of accomplishing this. In his "heterodyne receiver" an unmodulated sine wave radio signal at a frequency f" offset from the incoming radio wave carrier f" was applied to a rectifying detector such as a crystal detector or electrolytic detector, along with the radio signal from the antenna. In the detector the two signals mixed, creating two new "heterodyne" (beat) frequencies at the sum f" + f" and the difference f" − f" between these frequencies. By choosing f" correctly the lower heterodyne f" − "f" was in the audio frequency range, so it was audible as a tone in the earphone whenever the carrier was present. Thus the "dots" and "dashes" of Morse code were audible as musical "beeps". A major attraction of this method during this pre-amplification period was that the heterodyne receiver actually amplified the signal somewhat, the detector had "mixer gain".