According to Elgen Long (The Mystery Solved, Simon & Schuster, 1999) the two radio technicians sent from Pan Am's radio shop at Dinner Key to work on Earhart's radios were Louis Michelfelder and Robert H. Thibert. Long interviewed Thibert on November 2, 1991. Thibert told Long that on May 29 he checked the direction finder on NR1020 by taking bearings on local broadcast radio station WQAM and found "The direction finder gave good bearings with a definite minimum when the loop was swung to point at the station."
Citing his interview with Thibert, Long goes on at great length about problems the Pan Am radio techs had with Earhart's transmitter and what they did to fix it, but there is no mention a problem with the DF, let alone replacing it with a Pan Am unit.
So whom do we believe? Contemporary press reports or the 54 year-old recollections of the technician who actually did the work? Press reports, as we all know, are often wrong, but so are anecdotal recollections. Just as with the patch that replaced the lavatory window, the one type of evidence we have that we can rely upon is photography and photos of the airplane show no change in the DF antenna.