His PhD thesis was supervised by William C. Erickson and concerned the design and prototyping for an array at the Clark Lake Radio Observatory. Much of Fisher's career has involved radio astronomy instrumentation, including telescope feed design, radio frequency interference mitigation, and signal processing. He joined NRAO in 1972 at the Green Bank, West Virginia site. He was part of the team that conceived and designed the 100-meter Green Bank Telescope there. He moved to the Central Development Lab at the Charlottesville NRAO headquarters in 2005, where he retired in 2012 but continues to be active in instrumentation projects.