NR16020 antennas
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Ric Gillespie, ["Propagation Analysis," November, 2000, TIGHAR Tracks.
The other part of the equation seems to be the changes that were made to Earhart’s transmitting antenna prior to her second World Flight attempt. Originally, Western Electric had set up the vee antenna that ran from a mast on top of the fuselage to each vertical fin on the tail to be an appropriate length for Earhart’s two primary communications frequencies, 3105 and 6210 Kcs. The much lower 500 Kcs frequency required a much longer antenna which was provided by a “trailing wire” that was played out into the slipstream after the aircraft was in flight and reeled back in before landing. The wreck in Hawaii that ended the first World Flight attempt also wiped out the mast on the belly from which the trailing wire was deployed. During repairs back in California the decision was made to eliminate the trailing wire and lengthen the vee antenna on top of the fuselage to accommodate all three frequencies on the one antenna. The mast that supported the point of the vee was moved forward several feet. It was a terrible compromise that provided no meaningful capability to transmit on 500 Kcs while greatly complicating the problem of putting out a decent signal on 3105 and 6210. There appears to have been, however, another consequence to lengthening the vee. The new length made an excellent antenna for the unintended harmonic frequencies.