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Author Topic: Rethinking The Antennas  (Read 3561 times)

Andrew M McKenna

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Re: Rethinking The Antennas
« Reply #45 on: April 17, 2020, 02:55:22 PM »

My eyes are getting old ..... but what do you think that the object crossing the upper left corner of the 'navigation' window might be in the  'Miami taxi wire.png'? It looks like it crosses the same area of window that the rear connected antenna lead did in previous photos.

I'm confused.  'Miami taxi wire.png' shows the patch, not the navigation window and I don't see an object crossing the upper left corner of the patch.  The patch is new and shiny, so we see reflections of the people watching the plane taxi out.

I think he means the object that can be seen through both the starboard and port windows.  see this photo

Andrew
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Harbert William Davenport

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Re: Rethinking The Antennas
« Reply #46 on: April 17, 2020, 03:30:33 PM »

The third photo was taken March 12, 1937. The navigator's table has been installed (you can see the "goose neck" of the lamp) but features "B" and "C" are no longer present.  Also, the fuel tank vent line manifold "D" has been wrapped with wire(?) and there's a bundle of wire or cable "E" running to either the transmitter or the aft battery.

While there are a lot of eyes on this, please consider also this photo from approximately 3/3/37 showing electronics on top of the R1 fuel tank. In the 3/12/37 photo there seem to be cables extending from that same apparatus across the doorframe into the cockpit. What is that apparatus?

Dan Brown, #2408
   Could it be the coupler or coupling unit component of the Bendix Radio Direction Finding (RDF) system?
   That Bendix RDF system was installed in the Electra in Burbank from Friday, Feb 26 to about Friday, March 5, after Bendix radio expert Cyril Remmlein arrived there on Feb 26 from the east coast to supervise the installation. (See Timeline.)  That Bendix DF system replaced the Hooven DF system that had been in place in the Electra since the previous October.
   It is my understanding that the Bendix DF system had five key components: 1. the familiar overhead open loop antenna; 2. the coupling unit; 3. the Bendix DF receiver;  4. a ‘sense’ antenna; and 5. a remote control unit for operating the system from the cockpit.  (There was also a dial in the instrument panel that I will ignore for present purposes.)
   The Timeline shows published newspaper publicity photos of three of those components: the loop antenna, the remote control unit, and the receiver.  I have never seen a photo of the coupler unit, except for the one you’ve posted, if that is indeed the coupler, and perhaps a few other photos of the cabin like it, in which that black box is barely visible in the background.
   I would like to know more about the coupler, in part because of the likelihood that it was retained as a necessary part of the modified DF system that was in place in May for the second attempt.  In that modified system, the WE 20B communication receiver under the copilot seat was co-opted into doing double duty as the DF receiver, replacing the Bendix DF receiver which was eliminated from the modified system.  My understanding is that the coupler unit was still needed in its place, between the loop antenna and the WE 20B receiver. 
    For some time I labored under the misunderstanding that the remote control unit pictured in the photos being held by Remmlein was the same thing as the coupler unit, or incorporated all the needed coupling components within its small box.  Only recently have I realized my mistake, and I now believe that those coupling components were contained in their own separate larger box, the one we see in the photo posted by Dan Brown.
     I hope that Ric and our radio experts will weigh in to correct any misunderstandings on my part and to help further my understanding, as I lack radio expertise and have barely begun to research these issues.
H. Wm. (Bill) Davenport
3555R Prof of Philos, ret.
 
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Ric Gillespie

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Re: Rethinking The Antennas
« Reply #47 on: April 17, 2020, 03:39:43 PM »

I think he means the object that can be seen through both the starboard and port windows.  see this photo

I dunno what that is, unless it's the seam between the wing and aileron on the left wing.
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Ric Gillespie

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Re: Rethinking The Antennas
« Reply #48 on: April 17, 2020, 03:58:35 PM »

The "steam guages" beside the window are, top to bottom, altitude, outside air temperature, and indicated airspeed - all needed by the navigator to calculate True Airspeed.


     I hope that Ric and our radio experts will weigh in to correct any misunderstandings on my part and to help further my understanding, as I lack radio expertise and have barely begun to research these issues.

Thank you for making a distinction between me and a radio expert which - despite the best efforts of the the U.S. Army Signal Corps Advanced Radio Systems School at Ft. Monmouth, NJ - I most certainly am not.

That said, I think you nailed it.  Remmlein shows up to supervise the installation on Feb 26.  We don't know exactly when the RA-1 receiver was installed but it's present in the March 12 photo.  There are photos dated March 7 of AE posing with the about-to-be installed-loop. The photo Dan posted is circa March 3.  I think the box is the loop coupler.  There's no wire going forward because the loop has not been mounted yet.  BY March 12 the loop has been installed and the wire going from the box into the cockpit is headed straight for the base of the loop.
Nice work gentlemen.
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Ric Gillespie

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Re: Rethinking The Antennas
« Reply #49 on: May 23, 2020, 11:17:32 AM »

After more (much more) analysis of photos and written source material, we have reason to believe the antenna set-up on NR16020 at the time of the aircraft's disappearance was different than we previously thought.  As a reminder, there were three antennas on the Electra when it arrived in Lae.
• Dorsal vee wires from a mast on top of the fuselage to each vertical fin.
• A belly wire extending extending along the starboard underside of the fuselage.
• A loop antenna above the cockpit.

We have long believed the dorsal vee was used exclusively for transmitting and the belly antenna for receiving. The loop was used for DF (direction finding).  Hence, the loss of the belly antenna on takeoff conveniently explained why Earhart was unable to hear Itasca's voice transmissions on 3105 but when trying to DF on Itasca she was able to hear the transmission via the loop.

Earhart's Western Electric 13C transmitter had a receiver relay terminal which allowed the transmitter and receiver to share the same antenna. Our belief that this feature was not used was based on a photo of the cabin in which the terminals on the transmitter are visible.  The receiver relay terminal is clearly unused (see below).  However, that photo shows the cabin as it was when the airplane was equipped with the Hooven Radio Compass system and before the installation of a "navigator's station" in early March 1937.  At that time, the Hooven system was replaced with a Bendix system, a plywood table was built over the transmitter, and duplicates of some cockpit instruments (altimeter, airspeed indicator, and outside air temperature gauge) were installed for the navigator. A series of photos of Earhart sitting on the navigator's table, when correctly daed in sequence, shows the instruments were first installed on the cabin wall beside the window but were later moved down into the table.

In a photo of the cabin taken on March 12, 1937 (see below) there is a bundle of cables extending aft, secured to the fuselage fuel tank vent manifold.  The cables probably serve the duplicated cockpit instruments mounted in the table.  Included with the cables is a black wire that leaves the bundle and goes to a different destination.  It is most logically a line from the receiver to the receiver relay terminal on the transmitter, thus allowing the dorsal vee to be used for both transmitting and receiving.

Such a change would be a smart move.  The belly antenna was poorly situated for receiving unless the aircraft was close enough to the station to receive signals via "groundwave" (about 30 miles).  At greater distances, signals arriving from above as "skywave" (bounced off the ionosphere) are blocked by the fuselage. The March 12 photo is the last photo we have of the cabin, so we don't know what it looked like for the second world flight attempt.  We do know that, during the rebuild after the wreck in Hawaii and Manning's departure from the project, the trailing wire was not reinstalled and the Bendix receiver was removed, but there is no reason to think the ability to use the dorsal vee for both transmitting and receiving was not retained. That would explain why the port-side belly antenna was not replaced.  The Bendix direction finder needed a "sense" antenna to resolve "180° ambiguity." The starboard-side belly antenna could serve that purpose.

Of course, if the dorsal vee was being used to receive, we need a new hypothesis for why Earhart was not able to hear Itasca on 3105 but was able to hear the signals sent on 7500.  There is a simple explanation:

During the test flight on July 1st, Earhart was able to hear the station at Lae on Lae's frequency, 6522 kHz, so she must have had Band 4 (4000 to 10,000 kHz) selected on the WE20B. The was no need to change the setting when she left for Howland the next morning because she planned to receive hourly weather reports from Lae. Whether she ever heard them is debatable. If she later tuned the receiver to 3105 to listen for Itasca without switching to Band 3 (1500 to 4000 kHz) she wouldn't hear anything, but when she tuned to 7500 to use the loop, with the receiver still set on Band 4, she would hear the signal. The loss of the belly antenna on takeoff meant only that, without a “sense” antenna, the direction finder would not be able to resolve “180° ambiguity,” but the point is moot because the 7500 frequency was far above the DF’s 1500 kHz limit.
On the reef at Gardner, she must have realized her error because that evening she seems to have been able to hear Itasca on 3105 and send the dashes they requested that were heard by Achilles and New Zealand Star. She has to be on Band 3 to hear Itasca.  To later hear KGMB on 1320 kHz she has to be on Band 2 (550 to 1500 kHz).

If our conclusions are correct, there are two take-aways from this new research.
•  Earhart's failure to hear Itasca was due to operator error, not an accident on takeoff.
•  If Artifact 2-2-V-1a is from the Electra, it is most likely internal receiver feed line.  If the receiver under the copilot seat was connected to both the belly antenna and the transmitter in the cabin, there was much more internal receiver feed line aboard the airplane than we thought.




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Randy Conrad

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Re: Rethinking The Antennas
« Reply #50 on: May 23, 2020, 07:46:12 PM »

Ric...are you by chance seeing part of the window from the other side?
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Ric Gillespie

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Re: Rethinking The Antennas
« Reply #51 on: May 24, 2020, 07:33:01 AM »

Ric...are you by chance seeing part of the window from the other side?

I'm not sure I understand your question.  Part of the port-side cabin window is visible in the Jan/Feb 1937 photo. No window is visible in the March 12, 1937 photo.
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James Champion

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Re: Rethinking The Antennas
« Reply #52 on: May 24, 2020, 10:06:17 AM »

So, in the March 12, 1937 picture, the dorsal vee lead in is just-out-of frame to the right.

To get a 'repeater' of the cockpit altimeter and airspeed to the navigators table would have required two pressure tubes with a pitot-static port system.  I don't think the technology of the 30's would allow for mechanical diaphragm-pressure based instruments like these to be repeated electrically. I would guess-estimate that a 'repeater' for air temperature would need 3 to 4 wires.

What I'm getting at is the size/routing/bending of the shielded wire bundle we see in the March 12, 1937 picture explained fully by the needs of these three instruments? I state 'bending' as ideally these pressure based indicators would be routed with metal tubing. I say ideally as they might have used rubber hose, but would that lead to instrument accuracy issues? Is the shielding on this harness really an attempt to constrain flexible hoses from vibrating and/or changing size with pressure? Is what is marked in the photo as "Receiver line" actually one of the pressure lines?

I'm just pondering these issues outloud.
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Ric Gillespie

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Re: Rethinking The Antennas
« Reply #53 on: May 24, 2020, 10:18:36 AM »

So, in the March 12, 1937 picture, the dorsal vee lead in is just-out-of frame to the right.

Yes.

To get a 'repeater' of the cockpit altimeter and airspeed to the navigators table would have required two pressure tubes with a pitot-static port system.  I don't think the technology of the 30's would allow for mechanical diaphragm-pressure based instruments like these to be repeated electrically. I would guess-estimate that a 'repeater' for air temperature would need 3 to 4 wires.

What I'm getting at is the size/routing/bending of the shielded wire bundle we see in the March 12, 1937 picture explained fully by the needs of these three instruments?

I don't know.

I state 'bending' as ideally these pressure based indicators would be routed with metal tubing.

The wire bundle is new. I don't see any new metal tubing.

I say ideally as they might have used rubber hose, but would that lead to instrument accuracy issues? Is the shielding on this harness really an attempt to constrain flexible hoses from vibrating and/or changing size with pressure? Is what is marked in the photo as "Receiver line" actually one of the pressure lines?

I can't say it's not, but it's different from everything else in the bundle and it leaves the bundle as it comes down the wall and appears to be headed for a different destination.

I'm just pondering these issues outloud.

Pondering is good.
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William G Torgerson

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Re: Rethinking The Antennas
« Reply #54 on: May 27, 2020, 01:51:45 PM »

Mr. McKenna:

My apologies but I have been away from the forum for a bit. However this is the photo my comment was referring to. If you look at the 'high resolution' version of this photo you can see whatever 'it' is clearly crossing the upper left of the navigation window. To me 'it' appears to be inside the aircraft.

Bill
3046R
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Jon Romig

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Re: Rethinking The Antennas
« Reply #55 on: May 31, 2020, 11:38:22 AM »


If our conclusions are correct, there are two take-aways from this new research.
•  Earhart's failure to hear Itasca was due to operator error, not an accident on takeoff.
.

I accept it was not the loss of the belly antenna that directly resulted in the inability to receive, but is operator error the only possible, or even likely, conclusion?

* When your radio doesn’t receive, isn’t the first thing you do is flip the receiver’s controls on and off and into different positions to eliminate a transient fault and confirm that you have the proper setting?

* Is it possible that Earhart was so unfamiliar with this receiver that she wouldn’t properly position the band selector, and would not repeatedly check its position?

* When the belly antenna was ripped out (violently I might add) is there a possibility of damage to the other antenna and/or the receiver?

I am sure there are other possibly reasons.

We should not default to operator error until we have done our best to eliminate the alternatives.

Thanks,

Jon Romig
Jon Romig 3562R
 
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Ric Gillespie

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Re: Rethinking The Antennas
« Reply #56 on: June 01, 2020, 08:53:10 AM »

I accept it was not the loss of the belly antenna that directly resulted in the inability to receive, but is operator error the only possible, or even likely, conclusion?

It's a fair question.

* When your radio doesn’t receive, isn’t the first thing you do is flip the receiver’s controls on and off and into different positions to eliminate a transient fault and confirm that you have the proper setting?

I've never had a receiver fail but I've frequently failed to get a response when being handed off from one controller to another. The solution is to check that you've correctly selected the new frequency, try again, and if no response go back to the previous controller and request a different frequency. Today, changing frequencies is a simple matter of dialing it in.  For Earhart, changing frequencies was a multi-step process that may or may not involve changing bands.

* Is it possible that Earhart was so unfamiliar with this receiver that she wouldn’t properly position the band selector, and would not repeatedly check its position?

It was the same receiver the airplane was delivered with but she seems to have rarely used it.

* When the belly antenna was ripped out (violently I might add) is there a possibility of damage to the other antenna and/or the receiver?

It's hard to see how the loss of the belly antenna would have any effect on the dorsal antenna. The two were not connected.  The receiver itself was clearly working because she was able to hear Itasca on 7500.

We should not default to operator error until we have done our best to eliminate the alternatives.

I agree, but that's kinda what we did, and it fits a pattern.  Time and again with Earhart, communications problems are traceable to operator error, i.e. trusting Joe Gurr to set up her radios and antennas while the plane was being repaired, not being able to diagnose and repair a simple blown fuse which disabled the receiver for much of the world flight, incorrectly converting meters to kilocycles in Darwin, blaming the DF's failure to home on Lae during the testflight to being too close to the station, and ultimately, asking Itasca to send signals on a frequency her DF could not respond to.
« Last Edit: June 01, 2020, 08:55:27 AM by Ric Gillespie »
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Friend Weller

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Re: Rethinking The Antennas
« Reply #57 on: June 01, 2020, 12:53:55 PM »

Here's a puzzle...... <snip>... but what's the connection at "A" going down through the floor? 

Yup, definitely a ground lug - see the first photo below.

For Earhart, changing frequencies was a multi-step process that may or may not involve changing bands.

In reference to the second and third photos below: The band switch is the upper rightmost knob on the receiver remote control unit.  I can see that having to look AND reach across to a knob behind the yoke AND adjust the crank to tune to the correct frequency might have been one too many things to deal with when things became dicey as they reached the advanced LOP.  Under ordinary circumstances, it wouldn't be a big deal.....but Amelia and Fred were not in an ordinary situation.  Flying fatigue had to be a contributing element.

(Don't ask me how many times I've forgotten to switch the work truck out of 4WD until I was more than a ways off the mountain and on pavement....and that 4WD switch is right in front of me, I haven't been driving for 20+ hours, and I'm firmly on the ground!)   ;D
Friend
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« Last Edit: June 01, 2020, 05:28:04 PM by Friend Weller »
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