As a big fan of phasing type SSB,  I thought it might be of interest to some that the math and engineering work behind this type of audio phase shift network was done by Robert B. Dome of the General Electric Receiver Division.   No computers, just slide rules and brainpower back then, but his design provided a 90 degree phase shift with less error across the band of frequencies needed for transmitting speech.   It's described in his article "Phase Shift Networks" in Electronics magazine for Dec. 1946, which can be found at the World Radio History site.

Dome's design was the basis for the Barker and Williamson 350 / 2Q4 network that was affordable enough for the countless hams who followed the example of Tony Vitale W2EWL to create their own SSB transmitters,  both based on modifying plentiful and cheap ARC-5 transmitters  and in homebrew designs.  His design was also produced by Central Electronics and other comopanies in different form - even Millen made one!

Dome, aka W2WAM, is also credited for many technical innovations at GE, including frequency interlace color television modulation, which was compatible with existing black and white television sets but was not selected as the industry standard.

73, Bob W9RAN

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