Chuck, I was just trying to think of some reason why AE apparently thought she could home in on the higher frequencies that she could tune in on her radio receiver.
That, to me, is one of the $64,000 dollar questions.
Unfortunately, I haven't seen an answer to it anywhere.
Note the discrepancies:
June 25th at 2245GMT, the Coast Guard San Francisco office sent a radio message
... Mr. Putnam now at Oakland and advises Ms. Earhart at Bandoeng Java for repairs to motors and departure indefinite.
She will cable details communications from Port Darwin direct San Francisco and you will be given all information immediately. All communications from plane will be on 500, 3105, or 6210 kHz by voice, positions being given at 15 and 45 minutes past the hour.
Itasca adjust transmitter for possible use 3105 kHz for voice.
Direction finder on plane covers range of about 200 to 1400 kHz.
At 0720GMT, June 26th, Earhart cabled:
...
Itasca transmit letter A, position, own call letters, as above on half hour
at 7.5 MHz. Position ships and our leaving will determine broadcast times specifically. If frequencies mentioned unsuitable night work inform me at Lae. I will give long call by voice 3105 kHz quarter after hour, possible quarter to.
This contradicts the June 25th telegram that position reports would be given "given at 15 and 45 minutes past the hour." Jacobson: "It is unclear why Earhart wants the
Itasca to broadcast at 7500 kHz, since she is asking for code and cannot use that frequency for direction finding. The actual wording in the telegram is 7.5 megacycles."
At 1930GMT, June 26th, the San Francisco office of the USCG sent out a priority radio message stating
Following information from Earhart this date quote homing device covers
from 200 to 1500 and 2400 to 4800 kHz any frequencies not repeat not near ends of bands suitable unquote. ... assume continuous signals after her direction finder in range. See broadcast on quarter after and quarter before hour on 6210 and 3105 kHz. Am advising Earhart that
Itasca will voice radio her on 3105 on hour and half hour as she approaches Howland. ... Advice priority if adjustments Tare ten transmitter satisfactory for use on 3105.
The information on the 25th was that Earhart's DF equipment operated between 200 and 1400 kHz; now two ranges are given: "200 to 1500 and 2400 to 4800 kHz."Jacobson: "There is no contemporaneous documentation to verify that the information regarding the double frequency band of Earhart's RDF came from Earhart or George Putnam. Based upon the quoted passage, it should be taken at face value and accepted as coming from Earhart."
[9] The
transmission timeline shows that she asked for the letter A to be transmitted on 7500 kcs at 1928. At 1930, she reports that she heard the transmission, but could not get a null on it. This is the only transmission she acknowledges hearing from the
Itasca.
All I'm doing here is providing background for your question. Why didn't she understand her equipment?