The loop control box has LOOP TUNING printed on it. It has a tuning dial and a band selector. I guess it needed to be connected to a receiver for signal amplification, audio output and BFO function. The receiver would need to be tuned to the same frequency but would be limited to the frequency range of the loop control box. The loop alone will give two nulls. Combining the signals from the loop and the static antenna does not prevent the user finding the null but it gives a single null giving an unambiguous direction.

Quote from: Colin Taylor on March 16, 2026, 05:00:12 AMThe 7500kcs signal could not be received through the loop antenna because the loop control box could not be tuned above 1500kcs. Therefore it must be received through a static aerial.

The control for the frequency of the loop was in the one and only RECEIVER.

Amelia configured the RECEIVER to receive on 7500 kcs and connected it to the loop.

The loop could not do any DIRECTION FINDING on that frequency.

Those are two different issues.

If the loop was not acting as an antenna, it could not be used for direction finding.

The unit she was using employed only the loop for direction-finding. The more sophisticated unit that Hooven had designed that was originally installed on the aircraft used two antennas. It was able to resolve the question of whether the transmission was coming from ahead of or from behind the plane.

Hooven wrote a paper about the loss of the aircraft and crew.

The 7500kcs signal could not be received through the loop antenna because the loop control box could not be tuned above 1500kcs. Therefore it must be received through a static aerial.

However, according to Michael Everette it is possible that the upper two bands of the Western Electric receiver were connected to the dorsal aerial through switch gear in the transmitter.

https://tighar.org/Projects/Earhart/Archives/Research/ResearchPapers/ElectraRadios/ElectraRadios.htm#16

Alternatively the ventral receiver antenna was undamaged.

That means that the problem was to do with switch selection. To receive a morse signal on 7500kcs would require selection of the upper band, tuning 7500 AND selecting CW (or BFO).

Whatever the aerial configuration, a small adjustment of the tuning and deselection of CW would have enabled Earhart to receive a voice transmission on 6210kcs.

The undated picture shows the loop aerial, the loop control box (under the roof panel at left) the receiver remote control (to right of throttles by her left hand) and the five switch panel containing the CW switch (to the right of that)

Quote from: Colin Taylor on March 11, 2026, 05:02:57 AMSo, how could she tune 7500 but not hear anything on 3105 or 6210? I guess we will never know.

The loop antenna worked on 7500. She did not experiment with staying on that antenna and tuning to one of the other two frequencies. 

My guess is that after failing to DF on 7500, she then switched back to the circuit for the belly antenna, on which she never heard anything. 

One receiver, two antenna circuits. 

One antenna worked once. The other one never did.

Her transmission antenna -- on top of the plane -- worked well enough for Howland to record messages from her that increased in signal strength from 2:40 AM until 8 AM or so.

https://tighar.org/wiki/index.php?title=Transmissions_heard_from_NR16020

Thanks for the links. I agree with you. So, the 'Miami' photo apparently shows the Electra cockpit in a hangar at Burbank, California before the first start! The mystery box appears to be the Hooven ADF control box and I see the ADF left/right indicator in the instrument panel above the turn and slip.
Oh dear, I cannot believe what is written in Elgen Long's book? I thought the internet was bad enough!
So, I am inclined to agree that there was only one receiver, hence only one ventral aerial and the loop control box was connected to the WE receiver.

So, how could she tune 7500 but not hear anything on 3105 or 6210? I guess we will never know.

Quote from: Simon Ellwood on February 23, 2025, 06:13:46 AMHi Kenton,
In your August post you said "This fall I will publish a comprehensive report expanding on my earlier work." On your recent posts, however, I don't see links or attachments dated in the fall, only to your earlier work linked in August. Are you still working on the comprehensive report, or did you in fact publish it and I somehow missed it?
Thanks,
Jon

Jon You in August 2024 I mentioned publishing an update report on.  Life had other ideas.  I will eventually publish an update.

An analysis of the Sydney Island source is here:
2-2-V-1: Lockheed 10 or a C-47?

Diego,
Thank you for the interesting post.   

Matt (and Kenton),

Thanks for posting this.  The Ghost has done a lot of AE research, always does a great job, and has produced another impressive article. He posted here back in the days when there was still serious debate on the Forum, but he didn't survive the many purges (or become a paid member). 

I had corresponded with the Ghost a couple of years ago about Vinson's videos, but I didn't have the patience to sit through them and really absorb them. Nor did I fully understand the Chuck and Bob exchanges.  The Ghost has kindly reduced those videos to writing, explained Chuck and Bob's exchanges, and now everything makes sense.

Shout out to Chuck Varney too, just in case he ever checks in here. 

Matt,
Thank you for posting links to John Kada's interesting paper related to Earhart's last radio signals while still in flight.   The discussion of the TIGHAR/Bob's Donut Hole hypothesis versus the Rockwell-Collins/Nauticos investigation is thought provoking.  This link provides information on Nauticos' future expedition. Nauticos Expedition and Radio Research