Bob1370 said:"the guy who made the public-address announcements on MASH"
Wasn't that done by Gary Burghoff, who was very visible in the role of Radar and probably making those announcements in character, for at least part of the show's run--and didn't they have Jamie Farr (who played Max Klinger) do it late in the show's run as well? In short, didn't the PA job fall to the 4077th's company clerk, whoever he was?
Most of the M*A*S*H PA system announcements were done by actor Sal Viscuso.