Still from ROV video

[Gary LaPook]

Here's a little bit of info' on RDF antenna:
Airplanes in flight accumulate electric charges52,53 that cause radio noise interference.

O.K., I've been having fun but now it's time to cut to the chase. At the risk of giving away my age, when I was young (make that VERY young) I had an AM radio on the nightstand next to my bed. I would fall asleep listening to soft music in my bedroom lit by the warm orange glow from the radio's tubes shining out through the ventilation holes in the back of the radio. (For those who do not know what a radio tube looks like, I am attaching a photo of several types and also go here.) The back of the radio was made out of some kind of fiberboard. When I removed the back (they were made easy to remove so that you could replace the tubes when they burned out) I found the loop antenna mounted on the inside of the back. It was designed to work on the AM broadcast band, 535 kc to 1600 kc, just slightly above the "beacon band" (190 kc to 535 kc) which was the band used for radio direction finders, it still is. This is where the standard direction finder frequencies used in Earhart's time, 375 kc, 400 kc and 500 kc, 800 meters, 750 meters and 600 meters wave lengths. Itasca was transmitting homing signal on 500 kc/600 meters. The loop antenna inside my radio consisted of dozens of turns, or coils, of wire. There was a reason for this.

It turns out that a loop antenna designed for direction finding should contain a length of wire equal to 0.08 wavelength for optimum performance but it can also be tuned to work on nearby frequencies. So the loop antennas used on aircraft radio direction finders do not have just one or two coils, but many coils. Do the math. Looking at the photo of Earhart mugging with the antenna, it appears that the loop is about one foot (30 cm) in diameter. Multiply by Pi and the circumference is a little more than three feet, let's call it one meter. The loop was designed to cover wavelengths between 600 to 1500 meters, let's say it was optimized for the standard direction finder wavelength of 800 meters. Multiply the 800 meters by 0.08 and you find the amount of wire in the loop is 64 meters long. Since the circumference of Earhart's loop is about one meter then there had to be 64 coils of wire inside it. The picture from the ROV shows only two coils so it ain't an RDF antenna. (And yes, they use very fine wire so 64 meters does fit inside the static shield.)

Also, the static shield has to be made out of a non-magnetic, conducting material, usually copper or aluminum. Where did that go?

(Does anybody else remember the tube testing machines which, at least in Chicago, were found in drugstores, for some reason. When your radio stopped working you pulled the tubes and carried them down to the drugstore. Looking at a table on the self test machine, you found the listing for your tube, placed it in the right sized socket, followed the instructions for your type of tube, set the various switches and then read the meter. If the reading was not in the correct range then you had found the bad tube and you bought a replacement tube, they were kept in a locked cabinet making up the base of the testing machine, you had to call the druggist over. If the first tube tested O.K. then you tested the rest of your tubes until you found the bad one. Too bad Earhart didn't have a tube tester machine.)

gl

[richie conroy]

gary the df on howland weren't turned on anyway till at least 7am in the morning of disappearance because battery had run low during nite trying to contact amelia an thought it was not needed as she had fred noonan aboard,

in video footage of lae take off, u see fred helping amelia climb onto wing then proceed in to electra cockpit not bad for someone who is bladdered,

amelia telegram ed either her husband or newspaper stateing she was feeling illl due to petrol fumes

an that was before lae take off, so can imagine what it would be like fully loaded, no doubt fred being an hardcore drinker they say prob had straw going in to reserve tank didnt help

a few things bother me about the flight in general...

amelia on take off from lae, diverted round weather front, before joining planned flight path which add's at least an hour on to time of arrival ?

the electra was fine tuned to take off fully loaded, if tanks emptied 1 by 1 then correcting balance of weight due to one wing tank full to opp side tank empty would that give false reading on instruments ?

also if they corrected  flight path due to head wind - side wind, an didnt adjust these back as plane got lighter would it be possible while the compass states ur heading north still, they could have blowin well off flight path while still heading north on compass reading ?       

[Tom Swearengen]

John--
I didnt see any apparent threads on the nose end of this 'cylinder' to retain a tach cable. Might be there. I was going by the shape and apparent size of the target. About the size of a Bendix generator, or starter. May be the electric motor for landing gear retraction. I have no pictures of that, other than a large "flywheel" looking apparatus. I'll try to fing that pic. Insted of an instrument like a tach, it seemed larger in diameter like an electric motor.
I'm probably wrong.  But, we are seeing all sorts of different debris, and if the wings and undercarriage were torn off by the reef, well, the motor has to be somewhere. I looks to me that there is a random pattern so this debris field. Maybe If Richie and Jeff can string these pics together in like  panagram, we can study the debris field closer.
Tom

[John Joseph Barrett]

Gary,  I don't think we can write off the RDF just yet. What type(s) of wire were used for the coils and the inner loop? Seems to me that it would probably have been a thinner guage of wire to have been wrapped inside of the loop. Two dissimilar metals in a salt water environment is the perfect situation for a galvanic reaction which, I would think, be more than capable of dissolving a thin wire over the course of 75 years of submersion. I might be wrong, but I don't recall the plane being equipped with any sacrificial zincs. Not surprising as it was never intended to be immersed in salt water. I know that I've needed to change the zincs on my boats a couple of times and they've never spent 75 years in the water.  LTM- John

[Tom Swearengen]

As for the Louver looking thing, I dont recall anywhere on the airframe any louvers. Maybe in the cabin. But it does look like it has a finned configuration. Ideas?
Tom

[John Joseph Barrett]

Tom,  It wouldn't necessarily have to be a threaded connection. I have seen some that use a 'c' clip or have a squeeze type clip built into the end of the cable housing. Depending on how it was mounted, it might be a bit hard to reach up and unthread the cable connector where it might be easier to squeeze a clip to remove it. Again, we don't have anything definitive scale wise to go by, but in looking at various pictures of the cockpit there are diffeerent sizes of guages visible, some fairly large. You may be right, it could be a starter or generator as well. Who knows what got tossed where during th break up and following years.  LTM- John

[John Joseph Barrett]

Tom,  I surfed the web for a bit looking for a purpose for the louvers and came up empty thus far. To me they look like louvres and not slots. I play with old cars and not planes, but the oil coolers I have seen have slotted fins just like a radiator to allow the most unrestricted airflow possible. Louvers are more for directing the airflow one way or another. Maybe mounted up behind the panel to direct the outside, or even heated, air down toward our intrepid crew's feet? I don't know. I will kep looking.   LTM- John

[richie conroy]

can anyone make out a shape, or have a idea what this could be have been on it 2 hours an my mind has gone blank..  :-\

[richie conroy]

cud these objects be same thing ?

[Jeff Victor Hayden]

Yet again, while we were debating the RDF antenna 'coral outcrop' the answer was again staring us in the face. Take a look at the first image. The little blue hole is where the cable goes from the RDF antenna 'coral outcrop' through the fuselage roof into the cockpit. The yellow lines outline the 'imprint' of the mounting used to secure it to fuselage roof. There's even a part of the inner skin of the fuselage ceiling dropped down, again with convinient hole to route cable. The third picture is the mounting used to hold the RDF antenna 'coral outcrop' to the top of the fuselage which I posted before. The last picture is of a ditch and settle aircraft wreck, shallow water, with the RDF (it's in there somewhere). Note this wreckage hasn't had to endure the reef/waves/storms/tides of TIGHARs one or the 300 metre slide down a volcanic outcrop. That's why it looks so pristine, if you can make it out through the growth all over it. Photo courtesy of PacificWrecks.com, Kevin Denlay.

[richie conroy]

or do these match up better

[Jeff Victor Hayden]

or do these match up better

Did they carry parachutes? take a look at what Freds stood next to on the ground.

[Harry Howe, Jr.]

Gary
We only had one radio, a big cabinet piece of furniture in the living room.  Went to Wallgreen's Drug Store to test and get replacement tubes when radio crapped out.  A real chore, had to take the back off, look in to see if ya could spot the unlit tube (if ya were lucky), take them all out if ya weren't lucky, put them in a paper bag, walk down to the Wallgreens store, etc.  A real project.

During the War years my Grand Father had a crystal SW radio  and I used to listen to War news on the headset  I forget the station, prolly BBC or its wartime equivalent.  Pretty exciting stuff for a kid.

[Harry Howe, Jr.]

Richie
With respect to fuel usage and plane balance, pilots are taught to adjust the fuel usage from tank to tank with some frequency (say every half hour or hour ) as the flight progresses in order to maintain balance.

What AE did or didn't do is unknown to us.

[Gary LaPook]

Gary,  I don't think we can write off the RDF just yet. What type(s) of wire were used for the coils and the inner loop? Seems to me that it would probably have been a thinner guage of wire to have been wrapped inside of the loop. Two dissimilar metals in a salt water environment is the perfect situation for a galvanic reaction which, I would think, be more than capable of dissolving a thin wire over the course of 75 years of submersion. I might be wrong, but I don't recall the plane being equipped with any sacrificial zincs. Not surprising as it was never intended to be immersed in salt water. I know that I've needed to change the zincs on my boats a couple of times and they've never spent 75 years in the water.  LTM- John

Copper wire is used to make the coils inside the anti-static shield. All the coils were made out of the same wire so why are there two coils left? They should all be left or they should all be gone. And where is the anti-static shield which was made out of metal. The RDF antenna  should look like the one in this picture tht was posted later.


gl