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Author Topic: Failure to Communicate on 7500 kcs  (Read 27526 times)

Martin X. Moleski, SJ

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Failure to Communicate on 7500 kcs
« on: January 10, 2012, 09:12:20 AM »

Am I the only one who jumped to the conclusion that one possible reason for AE to tell Itasca that she was flying North and South on the (157/337) line was to help them DF her position?  Her technique may have been lacking, but knowing the direction a target is moving helps establish its location to a DF station. 

Yes, I think that this is a novel idea. 

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She obviously didn't understand that Itasca could not get a DF bearing on her frequency.

Yes.  That is one of the fundamental links in the accident chain.  Earhart seemed to have no grasp of the concept that both her DF equipment and that of the Itasa had frequency limitations.  The request to have the Itasca transmit the letter "A" on 7500 kcs makes no earthly sense to me.  So far as I know, we don't know where she got the idea that her equipment could get a bearing on that frequency.  She may have gotten some bad advice along the way.

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Too bad she didn't establish two-way communications when she had the opportunity.  She coulda asked questions on 3105 (am I getting louder?), and received answers on 7500 (_._ _ or _.).

I agree completely.  Why they didn't latch on to that lifeline and play twenty questions is, for me, one of the greatest missed opportunities that they had.  They knew a little Morse Code, just not enough to keep up with the requirements for getting the proper licenses and using it to decode transmissions in flight.  All they needed was to ask the Itasca to send some easily identifiable letter for "Yes" and some other letter for "No." 

Of course, then they would have to ask the right questions and figure out what to do about them.  That's not a trivial problem.  The Itasca probably would have asked them to transmit on a frequency within the range of the Itasca's equipment:

On 2040GMT, June 28, Itasca sent this message to Earhart

Itasca transmitters calibrated 7500, 6210, 3105, 500 and 425 kHz CW and last three either CW or MCW. Itasca direction finder range 550 to 270 kHz. Request we be advised as to time of departure and zone time to be used on radio schedules.

A transmission on 500 kHz would be ideal for the Itasca's declared DF range.  But Earhart had removed the trailing antenna intended for use on 500 kHz.  When she asked Itasca to take a bearing on her, she was transmitting on 3105 kHz--and the Itasca attempted but failed to get a bearing from her transmission.  The Itasca’s direction finder was designed to work only with lower frequencies (270 kHz to 550 kHz). 

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All she and Fred needed was a time machine and web link to TIGHAR for answers to their navigation questions.

When we perfect our time machine, we can send them the information that they need. 
LTM,

           Marty
           TIGHAR #2359A
 
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Harry Howe, Jr.

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Re: Failure to Communicate on 7500 kcs
« Reply #1 on: January 10, 2012, 11:08:26 AM »


Yes!  as in a simple A (._) for affirmative, and N(_.) for negative.  Did these two (AE?FN) have no instructions in flying and communication before they got a license?.  It's called Ground School!

When I was a student pilot I had it drilled into me that every communication began with the following information: Call letters, Position, Heading, Altitude, Conditions, Time, and Intentions. The acronym with which to remember the items was PHACTI (plural of Fact? hehe). Using this, AE's last transmission with Itasca at 0843 (Itasca Time) would have gone something like this, "Itasca, KHAQQ, near you on line 157/337, heading SSE.1000 feet, fuel low, 2025 Greenwich, Diverting to nearest land along LOP 337 to 157".
No Worries Mates
LTM   Harry (TIGHAR #3244R)
 
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Richard C Cooke

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Re: Failure to Communicate on 7500 kcs
« Reply #2 on: January 10, 2012, 04:34:40 PM »

Ah!  but then we would be discussing someone else that somehow sneaked through ground school without learning the basics.   ;D
rc
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Gary LaPook

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Re: Failure to Communicate on 7500 kcs
« Reply #3 on: January 10, 2012, 06:00:14 PM »


Yes!  as in a simple A (._) for affirmative, and N(_.) for negative.  Did these two (AE?FN) have no instructions in flying and communication before they got a license?.  It's called Ground School!

"WHEN UNDERTAKING VERY HARD ROUTES KEEP DIRECTION BY GOOD METHODS."

This is the mnemonic learned by all pilots of that era to remember the identification of the enroute beacon lights. These lights were spaced every ten miles and the ten Morse code letters used to identify them, in order were, W,U,V,H,R,K,D,B,G,M. (Nobody knows why these were chosen or why they were placed in that order.) They then repeated this sequence after one hundred miles. Earhart certainly had to be familiar with these ten Morse code letters.

Plus, it was reported that they could identify individual letters if repeated slowly. This means that they knew all of the Morse code letters but that they were not proficient enough to use them at a high rate of speed. They had to know all of them however or they would not be able to identify the individual letters no matter how slowly or how many times they were repeated.

gl
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Gary LaPook

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Re: Failure to Communicate on 7500 kcs
« Reply #4 on: January 10, 2012, 07:25:55 PM »

Am I the only one who jumped to the conclusion that one possible reason for AE to tell Itasca that she was flying North and South on the (157/337) line was to help them DF her position?  Her technique may have been lacking, but knowing the direction a target is moving helps establish its location to a DF station. 

Yes, I think that this is a novel idea. 



Jump back.

There are three reasons that this is not supported. First, you are ascribing a level of understanding of RDF to Earhart that obviously exceeded her level of understanding. Second, that would only make sense if she kept transmitting periodically, which she didn't do. And Third, that wouldn't work.   

"KHAQQ THIS IS NRUI, WE HAVE MEASURED A BEARING TO YOUR TRANSMITTER, IT IS EITHER NINETY OR TWO SEVENTY, WE CAN'T TELL DUE TO THE ONE HUNDRED EIGHTY DEGREE AMBIGUITY INHERENT IN RDF BEARINGS, OVER,"

"NRUI THIS IS KHAQQ I WILL RUN NORTH AND SOUTH TO ALLOW YOU TO RESOLVE THAT AMBIGUITY, OVER."

" KHAQQ THIS IS NRUI, NO DO NOT DO THAT AS THAT WILL NOT RESOLVE THE AMBIGUITY. YOU MUST PROCEED IN ONLY ONE DIRECTION AND SEND ADDITIONAL  SIGNALS AFTER TEN MINUTES AND WE WILL THEN BE ABLE TO RESOLVE THE AMBIGUITY, OVER."

See attached diagram.

gl
« Last Edit: January 10, 2012, 07:49:02 PM by Gary LaPook »
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John Ousterhout

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Re: Failure to Communicate on 7500 kcs
« Reply #5 on: January 10, 2012, 09:21:58 PM »

Gary,
You've clearly grasped what a knowledgable person might have been able to do with communications and access to a DF steer.  My point was that AE only had a "little knowlege" ( a dangerous amount) of how DF worked or how to use it.  Of all the things she might have said, why say she was on the 157 337 line at all, if she wasn't expecting some sort of help that (she thought) would benefit from that information?  I think she had a fundamental misunderstanding of how to use DF, and I thought her choice of what to say illustrated her misunderstanding.
Cheers,
JohnO
 
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Gary LaPook

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Re: Failure to Communicate on 7500 kcs
« Reply #6 on: January 10, 2012, 10:46:26 PM »

Gary,
You've clearly grasped what a knowledgable person might have been able to do with communications and access to a DF steer.  My point was that AE only had a "little knowlege" ( a dangerous amount) of how DF worked or how to use it.  Of all the things she might have said, why say she was on the 157 337 line at all, if she wasn't expecting some sort of help that (she thought) would benefit from that information?  I think she had a fundamental misunderstanding of how to use DF, and I thought her choice of what to say illustrated her misunderstanding.
I can't disagree with you.

gl
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Martin X. Moleski, SJ

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Re: Failure to Communicate on 7500 kcs
« Reply #7 on: January 10, 2012, 11:50:35 PM »

Why say she was on the 157 337 line at all, if she wasn't expecting some sort of help that (she thought) would benefit from that information?

Because it gives E/W longitude, in the absence of knowledge about their N/S latitude?

Because that is what they were doing?

It doesn't have to be related to direction finding.  That approach (pun intended; you may laugh now) wasn't working.
LTM,

           Marty
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Gary LaPook

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Re: Failure to Communicate on 7500 kcs
« Reply #8 on: January 11, 2012, 01:22:48 AM »




She obviously didn't understand that Itasca could not get a DF bearing on her frequency.
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Yes.  That is one of the fundamental links in the accident chain.  Earhart seemed to have no grasp of the concept that both her DF equipment and that of the Itasa had frequency limitations.  The request to have the Itasca transmit the letter "A" on 7500 kcs makes no earthly sense to me.  So far as I know, we don't know where she got the idea that her equipment could get a bearing on that frequency.  She may have gotten some bad advice along the way.
And why 7500, why not some other random number like 8364 or 6350 or 7937, etc.? And when did she come up with this number? The first time it is mentioned is in the June 27th radiogram from Earhart to Itasca. in which she requested Itasca to send the letter "A" and call letters "ON HALF HOUR 7.5 MEGACYCLES." The next day Itasca radioed to Earhart that "ITASCA TRANSMITTERS CALIBRATED 7500 6210 3105 500 425 KCS CW" and that "ITASCA DIRECTION FINDER FREQUENCY RANGE 500 TO 270 KCS." This message acknowledged AE's request for 7500 Kcs, (7.5 Mcs.) It is tempting to think that AE was just making a mistake on radio terminology and that she actually  wanted Itasca to transmit on a 750 meter wavelength (which is the same as 400  Kcs) which was a common direction finder wavelength. The problem with this idea is that in the same June 27th radiogram she requested "ONTARIO STANDBY ON 400 KILOCYCLES" so it is very unlikely she would request the correct 400 Kcs from Ontario and then use different terminology to request the same 400 Kcs (750 meter wavelength) signal from Itasca. And again on July 1st AE sent another radiogram requesting Ontario to transmit on 400 Kcs so that  appears to be the terminology that she knew how to use. ( I am using the obsolete terminology of "Kcs" and Mcs" rather than the modern usage of "Khz " and "Mhz" for consistency and to avoid confusion.)

Another theory is that she was using an experimental Bendix radio direction finder (RDF) that was designed to use high frequencies and that Bendix expected to get a marketing boost by her endorsement of that equipment after using it to find Howland. There are problems with this theory too. As far as I know Bendix never tried to sell an RDF that used high frequencies as there is no particular advantage to high frequency for RDF work. ( High  frequency direction finding, HF/DF also called "Huff-duff," was used in the war to take bearings on high frequency communication transmissions from U-boats so that they could be found and sunk and so that convoys could be detoured around the U-boats but this was completely different kind of equipment.) The standard frequencies, to this day, for RDF are still low frequencies in the 190 to 535 Kcs band (see paragraph  1-1-2 of the current Aeronautical Information Manual.) ( Technically these frequencies are in the low and medium frequency bands. The low frequency band extends from 30 Kcs to 300 Kcs and the medium frequency band goes from 300 Kcs to 3,000 Kcs or 3 Mcs. High frequency covers 3 Mcs to 30 Mcs. Why are the bands defined this way? Because they were actually defined by wavelengths in the early days of radio. High frequency covers wavelengths of 10 to 100 meters; medium frequency 100 to 1000 meters; and low frequency from 1000 to 10,000 meters.)

You would also think that even if AE was trying to do an experiment with a high frequency RDF that when it wasn't working out, and she was staring death in the face, she would have attempted to use 500 Kcs which Itasca was also transmitting on and which had been calibrated back in Lae. Itasca had also informed her that Itasca's RDF only covered 500 to 270 Kcs so it doesn't make sense when she asked itasca to take a bearing on her 3105 Kcs transmission. Both of these indicate that AE lacked any useful understanding of RDF.

Didn't anybody ever wonder why Itasca stated the range of their RDF as "500 to 275 kcs" instead of the expected "275 to 500 kcs?" It's because they were still using wavelengths for specifying the range of the radio, 600 to 1010 meters.

gl
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Martin X. Moleski, SJ

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Re: Failure to Communicate on 7500 kcs
« Reply #9 on: January 11, 2012, 08:15:34 AM »

Why 7500, why not some other random number like 8364 or 6350 or 7937, etc.? And when did she come up with this number?

I don't know.  The question has been asked before.  I imagine that it may have been suggested to her by someone in Lae as a "good frequency" for air-to-ground communication.  As things turned out, it was a good frequency--the message that she heard the letter "A" on it is the only mention in the logs of her receiving a transmission from the Itasca. 

I don't think we know exactly how she configured her receiver for direction-finding.  Itasca could not transmit voice on 7500 kcs.  If she had left things set up for direction-finding and asked for a voice transmission on 6210 kcs, she might have heard them.  That seems to me like another missed opportunity to solve the communications problem.  The reception on 7500 kcs shows that the receiver system did work on that frequency; it might also have worked on 6210.

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You would also think that even if AE was trying to do an experiment with a high frequency RDF that when it wasn't working out, and she was staring death in the face, she would have attempted to use 500 Kcs which Itasca was also transmitting on and which had been calibrated back in Lae. Itasca had also informed her that Itasca's RDF only covered 500 to 270 Kcs so it doesn't make sense when she asked itasca to take a bearing on her 3105 Kcs transmission. Both of these indicate that AE lacked any useful understanding of RDF.

Agreed.  Asking Itasca to transmit on 500 kcs is another problem-solving option that she missed.

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Didn't anybody ever wonder why Itasca stated the range of their RDF as "500 to 275 kcs" instead of the expected "275 to 500 kcs?" It's because they were still using wavelengths for specifying the range of the radio, 600 to 1010 meters.

Interesting.  No, I hadn't thought about it or made that connection.
LTM,

           Marty
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richie conroy

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Re: Failure to Communicate on 7500 kcs
« Reply #10 on: January 11, 2012, 01:49:17 PM »

dont know if this is ov any use but thought i would post it anyway

We are an echo of the past


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Martin X. Moleski, SJ

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Re: Failure to Communicate on 7500 kcs
« Reply #11 on: January 11, 2012, 05:04:52 PM »

dont know if this is ov any use but thought i would post it anyway

When you upload an image from elsewhere, would you provide a link to your source?

I presume it's Purdue, but by giving a link you make it easier to provide a reference later.

It's a fascinating telegram. 

I think it provides the information that then was sent by COMFRANDIV to Itasca:

Record No: 1548

From: COMFRANDIV
Action: ITASCA (PRIORITY)
Precedence Date: 06/26/37

FOLLOWING INFORMATION FROM EARHART THIS DATE

QUOTE

HOMING DEVICE COVERS FROM 200 TO 1500 AND 2400 TO 48 KILOCYCLES

ANY FREQUENCIES NOT REPEAT NOT NEAR ENDS OF BANDS SUITABLE

UNQUOTE

SUGGEST USING SUITABLE FREQUENCIES HAVING IN MIND UNCERTAIN CHARACTERISTICS OF HIGH FREQUENCIES.

USE 333 KILOCYCLES OR FREQUENCY IN THAT VICINITY AND TRY 545 KILOCYCLES AFTER TESTS WITH STATIONS YOUR LOCALITY TO DETERMINE WHICH IS BEST.

ADVISE IF IMPOSSIBLE TO PLACE TARE 10 TRANSMITTER ON 3105 KILOCYCLES.

EARHART AT LAE VIA TUTUILA EXACT FREQUENCIES SELECTED AND ASSUME CONTINUOUS SIGNALS AFTER HER DIRECTION FINDER IN RANGE.

SEE BROADCAST ON QUARTER AFTER AND QUARTER BEFORE HOUR ON 6210 AND 3105 KILOCYCLES.

AM ADVISING EARHART THAT ITASCA WILL VOICE RADIO HER ON 3105 ON HOUR AND HALF HOUR AS SHE APPROACHES HOWLAND.

REPAIRS MADE AND EARHART NOW AT SOURABAYA EXPECTS LEAVE DAWN THIS DATE FOR PORT DARWIN AND NEXT DAY FOR LAE.

ADVISE PRIORITY IF ADJUSTMENTS TARE TEN TRANSMITTER SATISFACTORY FOR USE ON 3105
LTM,

           Marty
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richie conroy

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Re: Failure to Communicate on 7500 kcs
« Reply #13 on: January 11, 2012, 06:09:54 PM »

We are an echo of the past


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richie conroy

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We are an echo of the past


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