Hiram Percy Maxim (September 2, 1869 – February 17, 1936) was an American radio pioneer and inventor, and co-founder (with Clarence D. Tuska) of the American Radio Relay League (ARRL). He originally had the amateur call signs SNY, 1WH, 1ZM, (after World War I) 1AW, and later W1AW, which is now the ARRL Headquarters club station call sign. His rotary spark-gap transmitter "Old Betsy" has a place of honor at the ARRL Headquarters.
He was the son of Sir Hiram Stevens Maxim, inventor of the Maxim Machine gun. In addition, he was the nephew of Hudson Maxim, an inventor of explosives and ballistic propellants. He had two sisters, Florence Maxim, who married George Albert Cutter, and Adelaide Maxim, who married Eldon Joubert, Ignace Paderewski's piano tuner.  Hiram was a mechanical engineering graduate, class of 1886, of the Massachusetts Institute of Technology (then a two-year course). 
Beginning in 1892 Maxim worked at the American Projectile Company of Lynn, Massachusetts, and tinkered nights on his own internal combustion engine. He admitted his ignorance of engine developments in Germany by Maybach, Daimler, and Benz, and he later explained that he "was staggered at the amount of time required to build one small engine." Furthermore, he was appalled once he finally achieved combustion. The engine "shook and trembled and rattled and clattered, spat oil, fire, smoke, and smell, and to a person who disliked machinery naturally, and who had been brought up to the fine elegance and perfection of fine horse carriages, it was revolting."
In early 1895 Maxim visited Colonel Albert Pope in Hartford which led to his being hired for the Motor Vehicle Division of the Pope Manufacturing Company. His vehicle was not ready in time for the Times-Herald race in November, but Maxim was able to get to Chicago and serve as an umpire. He rode with the Morris and Salom entry, the Electrobat II.
In 1899, with Maxim at the controls, the Pope Columbia, a gasoline-powered automobile, won the first closed-circuit automobile race in the US at Branford, Connecticut. Columbia continued to produce gasoline cars until 1913, and was also a major manufacturer of early electric automobiles and trucks.
Marriage and family
He married Josephine Hamilton, the daughter of the former Maryland Governor William T. Hamilton December 21, 1898, in Hagerstown, Maryland, and had a son, Hiram Hamilton Maxim, and a daughter, Percy Hamilton Maxim, who married John Glessner Lee, the grandson of John J. Glessner. The John J. Glessner House designed by Henry Hobson Richardson is now a Chicago landmark. Percy Maxim Lee (1906-2002) was president of the League of Women Voters from 1950–1958, and testified in the U.S. Senate against Senator Joseph McCarthy in 1955.
He created the ARRL in 1914 as a response to the lack of an organized group of "relay" stations to pass messages via amateur radio. Relaying messages allowed them to travel farther than any single station's reach at the time.
Maxim founded the Amateur Cinema League in New York in 1926; he was elected president. The Amateur Cinema League published a monthly journal, Movie Makers .
Maxim wrote an amusing account of his youth in the book A Genius in the Family: Sir Hiram Stevens Maxim Through a Small Son's Eyes . This book was adapted to the screen as So Goes My Love . H. P. Maxim recounted his days as an automobile pioneer in his book Horseless Carriage Days and also wrote the book Life's Place in the Cosmos , an overview of contemporary science that surmised life existed outside of earth.
His daughter, Percy Maxim Lee (1906–2002) became President of the League of Women Voters of the United States and was appointed by President Kennedy to the Consumer Advisory Council, which she later chaired. She was an advocate for debates by presidential candidates, and an opponent of the abuse from Senator Joseph McCarthy.
Hiram Percy Maxim was returning to his home in Hartford, Connecticut, in February 1936, from a trip to California to visit the Lick Observatory. He fell ill and was taken from the train to a hospital in La Junta, Colorado, where he died the following day, February 17, 1936. Hiram P. Maxim was buried in the Rose Hill Cemetery (Maryland) in Hagerstown, Maryland, in the Hamilton family plot belonging to his wife's family.
- : Motor vehicle (battery electric vehicle)
- : Motor vehicle running gear
- : Electric motor vehicle
- : Motor road vehicle
- : Silent Firearm Issued March 30, 1909.
- Life's Place in the Cosmos , New York: D. Appleton, 1933.
- A Genius in the Family , New York: Harper, 1936.
- Horseless Carriage Days , New York: Harper, 1936.
- Schumacher, Alice Clink, Hiram Percy Maxim, Father of Amateur Radio , Great Falls, MT: Schumachers, 1970.