Swanson worked for Collins Radio in Cedar Rapids, Iowa and Dallas, Texas before joining Gates Radio in Quincy Illinois, which was later bought by Harris Corporation. Swanson worked for Harris for 35 years until retirement in 1999, primarily on the design of high efficiency amplitude modulation transmitters. His work led to a series of patents on various types of high efficiency modulation, and led to the first commercial implementation of pulse duration modulation system, and later progressive series modulation, polyphase PDM, and digital amplitude modulation. Swanson's patents led to almost all AM broadcast transmitters being designed using digital modulation techniques, and made AM vacuum tube transmitters obsolete. Swanson designed and developed a 2 Million Watt transmitter for the Voice of America. It still stands as the world's most powerful AM Broadcast transmitter ever made. One of his last works was a paper, "Performance of Modern AM Modulation Methods for Linear Digital Broadcast Applications," co-authored with John DeLay.
Honors
Swanson was a made a Harris Fellow, the highest honor given to an employee of that company. After retirement, Harris created a scholarship in Swanson's name at the John Wood Community College in Quincy, Illinois for the study of radio broadcast technology. Phillip W. Farmer, former Harris Chairman, President and CEO, said, "Mr. Swanson, a Senior Scientist at the Broadcast Communications Division has become a radio engineering legend in his own time. It is believed that no one has contributed more to the advancement of AM broadcast radio transmitters than Hilmer Swanson. Most famous are his PDM and PSM modulation techniques, and his "Crown Jewel"—the digital AM generation technology for Harris' DX series AM broadcast product Line." In 1990, Swanson received the National Association of BroadcastersEngineering Achievement Award. He was an honorary member of Society of Broadcast Engineers, and a life member of Institute of Electrical and Electronics Engineers and the Sigma Xi Science Honor Fraternity. Swanson was awarded at least 28 patents in at least six countries
Later life
In his retirement, Swanson and his wife, Carolyn, performed missionary work in Palau, Chile and Estonia working to establish Christian AM broadcast radio stations. He was survived by three sons, a daughter, and their families.