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Author Topic: Research needed - RDF change in Miami?  (Read 2619 times)

Clarence Carlson

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Re: Research needed - RDF change in Miami?
« Reply #15 on: March 28, 2020, 01:59:33 PM »

If I am following this correctly it had been established that:

A. The RA1 receiver was removed after the accident on March 20 to save weight, along with the trailing wire antenna. That leaves us with the WE receiver.
B. Chater's report confirms the ability to receive 500 kHz, establishing that the WE receiver tuned a range of 485-1200 kHz (as noted by Brandenburg)

Now I am scratching my head, my question is: how would it be possible to receive KGMB at a frequency of 1320 kHz? History of Broadcasting in Hawaii I sense I missed something. KGU broadcasting at 760 is, of course still within the receivers tuning range.
Clarence Carlson
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Ric Gillespie

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Re: Research needed - RDF change in Miami?
« Reply #16 on: March 28, 2020, 03:05:08 PM »


B. Chater's report confirms the ability to receive 500 kHz, establishing that the WE receiver tuned a range of 485-1200 kHz (as noted by Brandenburg)

Now I am scratching my head, my question is: how would it be possible to receive KGMB at a frequency of 1320 kHz?

We know she could receive on 3105 and 6210, so the receiver did not top out at 1200. Hearing KGMB on 1320 would not be a problem.
Going back to Mike Everette's radio analysis (https://tighar.org/Projects/Earhart/Archives/Research/ResearchPapers/ElectraRadios/ElectraRadios.htm#12) The standard 20B had four bands:
200 - 400
550 - 1500
1500-4000
4000-10,000

Mike was referring to changes in Band 2.

« Last Edit: March 28, 2020, 03:25:16 PM by Ric Gillespie »
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Clarence Carlson

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Re: Research needed - RDF change in Miami?
« Reply #17 on: March 28, 2020, 07:59:17 PM »

Thanks Ric.

I should have been a little more specific. Band 2 on the modified WE receiver now ends at 1200 kHz. Band 3 is listed as starting at 1500 kHz. So the modifications applied to the broadcast band (making it possible to receive 500 kHz) seems to have created a "hole" between 1200 kHz and 1500 kHz. Which is where 1320 kHz lies. Hence the head scratching.
Clarence Carlson
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« Last Edit: March 28, 2020, 08:03:38 PM by Clarence Carlson »
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Ric Gillespie

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Re: Research needed - RDF change in Miami?
« Reply #18 on: March 29, 2020, 09:58:06 AM »

I should have been a little more specific.

I should have been a little less dense.

Band 2 on the modified WE receiver now ends at 1200 kHz. Band 3 is listed as starting at 1500 kHz. So the modifications applied to the broadcast band (making it possible to receive 500 kHz) seems to have created a "hole" between 1200 kHz and 1500 kHz. Which is where 1320 kHz lies. Hence the head scratching.

Of course, we don't know for sure exactly what changes, if any, were made to the receiver. However, we do have a new historical document courtesy of Earhart researcher Les Kinney (see below).  It appears to be a Western Electric press release dated February 17, 1937 written by E. J. Quimby of the Western Electric Information Department, describing the work done on Earhart's Electra during her visit. Quimby is the guy in the photo attached to my earlier post standing beside AE sitting on a step ladder.  AE is holding a 20B remote.  The reverse side of that photo (courtesy of TIGHAR member Larry Inman's "Remember Amelia" collection) is attached below.  The photo probably accompanied the press release.

I find several things about the press release interesting.
•  It's important to note that Quimby is a PR man, not a technician, which may account for some of the ambiguity in the wording.
•  Quimby begins by saying, "When Amelia Earhart left Newark Airport shortly before 3 o'clock this afternoon, her Lockheed Electra plane carried a complete installation of the latest radio aids to aerial navigation." I find it interesting
he says "latest aids to aerial navigation," not "communication."  When AE left Newark, the plane still had the Hooven Radio Compass.  Western Electric had nothing to do with the Hooven installation, so why the puff about navigation?   Three days earlier, as the telegram she sent to Mantz from New York confirms, she had decided to swap out the Hooven Radio Compass for a Bendix system.  Was Western Electric aware of the impending change?
•  Quimby says, " Her standard Western Electric type 13 transmitting equipment has been specially modified for the round-the-world flight so that she can communicate with ships at sea and shore marine stations on a crystal controlled frequency of 500 kilocycles."  This is entirely in agreement with Tinus' later description of changes made to the transmitter. Does Quimby's word "communicate with ships at sea" imply two-way communication?
•  Quimby "The type 20 [notice he does not say 20B] radio receiver may be employed for either telegraphy or telephony and covers the frequencies necessary to receive beacon signals, commercial broadcast stations, aircraft and police radio stations, amateurs, and various frequencies employed by foreign radio stations."  That sounds like a standard 20B.
• Quimby then describes the "diminutive remote control unit mounted directly on the instrument panel."  That's the 27A Remote AE is holding in the photo.  I'm quite sure (but I'll double check) the plane has had a 27A Remote since shortly after it was delivered in 1936.  If there has been no change to the receiver, why are they installing a new remote?

Getting back to the original question, if Earhart's receiver cannot tune to KGMB, how does that change our assessment of the post-loss radio signals?
« Last Edit: March 29, 2020, 10:00:34 AM by Ric Gillespie »
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Ric Gillespie

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Re: Research needed - RDF change in Miami?
« Reply #19 on: March 29, 2020, 10:42:21 AM »

Yep, the 27A Remote was included in the original (May 21, 1936) specs for the airplane.  It was, supposed to be installed in the control box lid. I'm not sure where the "control box lid" was.  All photos show it in the instrument panel "shelf" on the right side of the cockpit.
The 20B receiver was originally supposed to be installed on top of the fuel tanks in the cabin but they ended up putting it under the copilot's seat.

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Clarence Carlson

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Re: Research needed - RDF change in Miami?
« Reply #20 on: March 30, 2020, 12:27:52 PM »

"Getting back to the original question, if Earhart's receiver cannot tune to KGMB, how does that change our assessment of the post-loss radio signals?"

It would seem to be a question worthy of discussion. I've tried to think of a way that the receiver might still be able to tune beyond the frequency specifications but I can't quite get there. Maybe someone else has some thoughts on this.


Clarence Carlson
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Ric Gillespie

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Re: Research needed - RDF change in Miami?
« Reply #21 on: March 31, 2020, 10:28:42 AM »

Bob Brandenburg and I have been reviewing the question.  It's clear that Earhart was hearing KGMB.
Below are a few references to the Post-Loss Signals Catalog.  Earhart was sending dashes long before KGMB began asking her to:

Message 16 Itasca asks Earhart to send long dashes
Message 17 long dashes heard by Achilles on 3105
Message 18 dashes heard by New Zealand Star on 3105
Message 19 “generator start and stop” herd by Itasca on 3105
Message 26 long dashes on 3105 heard by Ft. Shafter
Message 27 long dashes and weak voice heard by COMHAWSEC on 6210
Message 41 long dashes on 3105 heard by COMHAWSEC
Message 54  KGU asks Earhart to transmit
Message 55 PAA Mokapu hears unintelligible voice on 3105
Message 63 PAA Mokapu hears two long dashes in apparent response to first KGMB broadcast
Message 66 COMHAWSEC hears carrier and voice on 3105 at end of KGMB broadcast
Message 100 PAA Mokapu heard KGMB request Earhart to send four dashes, and heard 4 dashes on 3105 immediately following the broadcast. Mokapu then asked KGMB to repeat the broadcast, to verify the response, and KGMB did so. Mokapu heard two dashes immediately following the second broadcast. Mokapu said that KGMB repeated the broadcast message to Earhart at half hour intervals “during the evening.” Mokapu obtained a radio direction finder bearing of approximately 215° on the source of the dashes.
Message 101 COMHAWSEC heard “carrier broken” – i.e. dashes – signals responding to the 0630Z KGMB broadcast
Message 103  Navy Radio Tutuila hears series of 4 dashes in response to KGMB broadcast
Message 104  Ditto 10 minutes later

The bearing Mokapu took (Message 100) pretty much proves she was hearing KGMB.

Bob points out that the logical way to modify the 20B receiver to cover 500 kHz would be to extend the upper end on Band 1 to 500 or 550, rather than alter the broadcast band coverage of Band 2.
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Clarence Carlson

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Re: Research needed - RDF change in Miami?
« Reply #22 on: April 01, 2020, 12:32:02 PM »

Agreed. As a long time amateur radio op the Post Loss signals analysis are mostly what brought me to TIGHAR. I've always thought the KGMB data were very persuasive. But if that data impeaches Michael Everette's analysis of the Electra radio coverage then shouldn't that information be revisited? As it is the website presents conflicting data that would seem to be consequential.
Clarence Carlson
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Ric Gillespie

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Re: Research needed - RDF change in Miami?
« Reply #23 on: April 01, 2020, 01:09:09 PM »

But if that data impeaches Michael Everette's analysis of the Electra radio coverage then shouldn't that information be revisited? As it is the website presents conflicting data that would seem to be consequential.

As a matter of policy we don't "correct" research bulletins.  They are a snapshot in time and many are now obsolete, but they are valuable as an historical record of our investigation. 

I can't change Mike Everette's analysis.  His analysis is generally excellent but he should not have said, "As the requirement for 500 KHz operation existed in Earhart’s case, the Band 2 tuning range was factory modified to 485-1200 KHz, covering the lower frequencies at the expense of the upper part of the broadcast band."  That was an opinion, not a fact.  Our current opinion is different but we still don't know for sure how her receiver was set up.
« Last Edit: April 01, 2020, 03:12:27 PM by Ric Gillespie »
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Clarence Carlson

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Re: Research needed - RDF change in Miami?
« Reply #24 on: April 01, 2020, 02:18:47 PM »

Thanks Ric. That does clarify the matter.
Clarence Carlson
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