Why did Earhart have so much trouble with radio communications?
3. Earhart switched radio frequencies at a critical time for radio transmissions and lost ground contact with the Coast Guard Cutter Itasca. There was considerable comment from many sources that it was an overt attempt to establish a spy mission; however, at the time of day that the switch was made, it was established procedure to change to the daytime frequency of 6210 KC from 3105 KC. These two frequencies are called harmonic frequencies (6210 is double 3105), and at certain hours of the day they “bleed” into one another. Thusly, Earhart made another serious mistake in selecting her departure time from New Guinea. Arriving in the vicinity of Howland Island at 8:00 A.M. in the morning Howland time meant that the night time frequency of 3105 would be fading and 6210 would be bleeding over taking its place. However, 3105 did not fade and 6210 was not on line at the time the switch was made. It was an impending doom to the Earhart flight. Communication with the Itasca was lost.
