Buffalo and Philadelphia (including Camden, and
undoubtedly RCA's plant as well) were the last
hold-outs of two-phase power in the U.S.

Are you saying that is what inspired RCA to build these transmitters with a two
phase feed to the rectifiers, I think they were the BTA-5G, BTA-10G, BTA-5H,
and BTA-10H?


I am hypothesizing that RCA utilized some ingenuity and well-known (to
two-phase aficionados) engineering techniques to make an unusual box which had
some unique cost-savings features.


To avoid confusion I call it a 4 pulse, or 6 pulse rectifier, as the case may
be.


However "incorrect" it may be, the literature calls these "four phase" and "six
phase".

"Twelve phase" is also employed. This is really three-phase, full-wave, using a
"zig zag" transformer.