The San Francisco Bay Area was an early center of ham radio with about 10% of the operators in the United States. William Eitel, Jack McCullough, and Charles Litton, Sr., who together pioneered vacuum tube manufacturing in the Bay Area, were hobbyists with training in technology gained locally who participated in development of shortwave radio by the ham radio hobby. High frequency, and especially, Very high frequency, VHF, transmission in the 10 meter band, required higher quality power tubes than were manufactured by the consortium of RCA, Western Electric, General Electric, Westinghouse which controlled vacuum tube manufacture. Litton pioneered the glass lathe which made mass production of reliable high quality power tubes possible.