Visualising the pre-loss radio signals
I have taken the time and signal strength data from the Itasca radio logs and produced a bar-graph depicting the time-line from about 19:00 Itasca Local Time (ILT) on the 1st July 1937 to 10:39 ILT on the 2nd. The graph displays the times of the Itasca transmissions and the change-over times of the radio-men on duty. It then shows the times of Earhart's radio schedule: transmitting on the quarter-hour and three-quarter-hour while listening out on the hour and the half-hour; and the times of the actual radio signals received by Itasca and Nauru Island, with the amplitude of the bars representing the signal strength. Also shown are the approximate time estimates of the waypoints.
On the chart is shown the direct track between Lae and Howland Island with the waypoints at 200nm intervals and the time-estimates based on the forecast winds and corrected for the position report at longitude 159E (POS 159) just before waypoint 4. Earhart's radio transmissions are plotted on the six-degrees left offset track which was the result of the difference between the forecast wind and the actual wind. All the times are Itasca Local Time.
The first thing to notice is that when Bellarts and Thomson are on duty they stick carefully to Earhart's radio schedule, transmitting on the hour and half-hour and listening-out for Earhart's transmissions on the quarter hours. However, when Galton comes on duty at 07:00 he will have been told that Earhart is inside 200nm and starting to be heard but he does not follow Earhart's schedule and there is a veritable blizzard of radio calls as he tries to make contact.
The 07:15 and 08:15 calls are missed although Bellarts is there at 07:42 when Earhart calls '...we must be on you...gas is running low... '. The last call heard was at 08:43 ILT and things calm down a bit around 09:00 but order is not fully restored and for some reason no more calls are heard. You can see how some of the missed calls may have been 'stepped-on' by Itasca transmitting at the 'wrong' time.
There is a conspicuous gap in Earhart's transmissions with only one unreadable signal between 22:30ILT and 02:45ILT. This offers evidence of the radio transmission pattern having somewhat of a doughnut- ring pattern, as the sky-wave and ground-waves interfere.
The position of the Electra at 10:30 UT (23:00 ILT) is shown, when Nauru Island heard Earhart report '...a ship in sight...'
An interesting exercise but unfortunately, nothing new to be learned.
Thanks, Colin.
A very interesting exercise indeed!
QuoteWhen Galton comes on duty at 07:00 he will have been told that Earhart is inside 200nm and starting to be heard but he does not follow Earhart's schedule and there is a veritable blizzard of radio calls as he tries to make contact.
... possibly stepping on some of her transmissions.
So sad, even after all of these years of thinking about the case.
So near and yet so far!
I am puzzled by the absence of a distress call.
This analysis ends at 10:39ILT which is the end of page three of Bellart's donated material, which is available on-line and is also the time that Captain Thomson thought she was out of fuel and set off to look for her. But I calculate that Earhart could have flown until 11:54. There are many more pages of Itasca radio logs on microfilm in the Coastguard archive. Has anyone examined them for perhaps unreadable signals which were overlooked at the time?
"We must be on you but cannot see you" could be taken for a distress call. She had gas and the Electra was flying normally so perhaps she didn't thing she was in "distress."
In her last message, AE also hinted that she was switching to her daytime frequency.
| 2013 | 0843 | 3105 | Itasca | "KHAQQ to Itasca we are on the line 157 337 (https://tighar.org/wiki/index.php?title=Last_words) wl rept msg we will rept this on 6210 KCS (https://tighar.org/wiki/index.php?title=Frequency,_wavelength,_and_antenna_tuning#Daytime.2Fnighttime_frequencies) wait, [(3105/A3 S5 (?/KHAQQ xmission we are running on N ES S line) (https://tighar.org/wiki/index.php?title=LOP)]" |
Neither the repetition on 6210 KCs nor any other transmission was logged from AE that day.
AE's daytime frequency did not function well on her departure from Lae:
| 0000 | | 6210 | Chater (http://tighar.org/Projects/Earhart/Documents/Chater_Report.html) | The departure from Lae took place at 0000 GMT. No transmissions from the plane were heard until four hours later. |
| 0418 | | 6210 | Chater (http://tighar.org/Projects/Earhart/Documents/Chater_Report.html) | "Height 7000 feet, speed 140 knots" then some remark concerning "Lae" then "everything OK." |
| 0519 | | 6210 | Chater (http://tighar.org/Projects/Earhart/Documents/Chater_Report.html) and Collopy (http://tighar.org/Projects/Earhart/Documents/Collopy_Letter.html) | At 0519 GMT, Earhart again broadcast a message on 6210 kHz. Chater reports: "Height 10000 feet position 150.7 E 7.3 S cumulus clouds everything OK."[1] (https://tighar.org/wiki/index.php?title=Transmissions_heard_from_NR16020#cite_note-1) Collopy (https://tighar.org/wiki/index.php?title=Collopy) states: "At about 3 PM local time a message came through to the effect that they were at 10,000 feet but were going to reduce altitude because of thick banks of cumulus clouds."
|
In saying this, I am presuming that she stuck to her transmission schedule after takeoff and that because of the peculiar characteristics of her antenna on that frequency on that day, it did not work well at short distances.
Martin I agree. The most plausible explanation is that the dorsal V-aerial configuration gave a very weak signal in the aircraft six o'clock position when the tail was pointing at the ground station and especially on 6210kcs. Same issue as during the departure from Lae.
Earhart's last message mentioned going North and South meaning that a 180 degree turn was to be made. Since the signal strength had been sustained up until the 08:43 transmission, the course reversal must have happened shortly after that last transmission.
In her last message she interjected the word '..wait'.. . That could only have been directed to Noonan who must have been trying to draw her attention by poking her with the stick they used to pass notes. What was he trying to tell her? Time to make that 180 degree turn.
I don't think Fred needed a stick on the fatal flight.
I think the navigator's station was removed altogether after the repairs at Luke Field.
He sat in the co-pilot's seat, which would have made cooperation much easier, even though some notes may have been necessary when sign language failed.
Quote from: Martin X. Moleski, SJ on August 13, 2026, 09:28:39 PMI think the navigator's station was removed altogether after the repairs at Luke Field.
I should have thought that Noonan would need a plotting table for his charts and access to both side windows for astro sightings and for use of the pelorus sight. Also he needed access to the drift sight.
Quote from: Colin Taylor on August 14, 2026, 02:52:51 AMI should have thought that Noonan would need a plotting table for his charts and access to both side windows for astro sightings and for use of the pelorus sight. Also he needed access to the drift sight.
From Ric5/30/00
https://tighar.org/Projects/Earhart/Archives/Forum/Highlights81_100/highlights90.html
QuoteMaking good celestial obversations from an airplane in flight was a bit of a problem. On the Pan Am "Clippers" it was solved by a sliding hatch in the "roof." On NR16020 it was initially solved by installing a big flat glass window on the starboard side of the cabin back in what was, on the airline version, the lavatory. A flat glass window was also installed in the cabin door on the port side. Sometime between when the airplane came out of the repair shop in Burbank on May 19, 1937 and the time it departed Miami on June 1st, the big window on the starboard side was skinned over with aluminum. We don't know why, but in a telephone conversation I had with Earhart's mechanic Ruckins "Bo" McKneely before he died, he said (I'm paraphrasing), "That Noonan fella didn't hold with all the fancy navigation arrangements and said he could just take his sightings through the windshield up front."
During WWII aircraft used a plexiglas bubble called an "astrodome" installed in the upper fuselage for celestial observations, but I suspect that in 1937 the technology did not yet exist to fabricate an optically correct bubble.
As for Noonan missing his mark; it was never the plan for Fred to hit Howland by DR and celestial alone. He and everyone else knew that, unless he was phenominally lucky, assistance from radio navigation would be necessary to find Howland within the time constraints imposed by the flight's fuel reserves.[/i] In the end, no help from the radio was forthcoming and Fred was left to do the best he could with what he had.
Emphasis added.
I guess that if Fred did really plan to do all of his navigating from the cockpit, he may have not used the pelorus at all.
That, in turn, might have affected his estimates of wind speed and direction.
In a sense, they were on death row when they took off from Lae.
Fred did not know until it was far too late that there would be no two-way conversations with the Itasca crew.
By the time he found out, his last reliable observation was when they saw the sun at dawn, which told them they were on the line of the terminator between night and day. He drew that line on his map and used dead reckoning to estimate when they had reached the parallel line drawn through Howland Island. That, in turn, explains the last transmission: "We are on the line 157 337."
Hi Everyone
What I am really asking is please would someone in the USA (maybe one of our fantastic TIGHARS) go to the Coastguard microfilm archive and retrieve a copy of the Itasca radio logs for the two hours after 10:39 ILT?
I want to see whether there are unreadable signals or whether Itasca was still transmitting and stepping on Earhart's transmission schedule.
Cheers
Colin
Those records have been examined numerous times.
They have been incorporated into the PDF of all radio signals, including telegrams, that is on the TIGHAR website.
Quote from: Randy Jacobson on August 15, 2026, 07:08:45 AMThose records have been examined numerous times.
They have been incorporated into the PDF of all radio signals, including telegrams, that is on the TIGHAR website.
Here is a page about some of Randy's major contributions to TIGHAR:
https://tighar.org/wiki/index.php?title=Randall_S._Jacobson,_Ph.D.
This page has links to the Jacobson Databases:
https://tighar.org/wiki/index.php?title=Jacobson_Databases
The same set of links are available in HTML:
https://tighar.org/Projects/Earhart/Archives/Research/JacobsonDatabase/JacobsonDB.html
Randy is a most amazing man. If he and I disagree, I try to figure out where I went wrong.
In my view, if he says that the records have been checked, they have been checked.
Thanks, Marty. I thought I had individual PDF's of the Itasca logs somewhere, but apparently not.
Bob Brandenburg also examined all of the post loss messages and signals and tried to determine the validity of them based upon radio propagation algorithms.
Once Itasca determined AE was down, there was little apparent need to continue monitoring her frequencies at the scheduled times. The Itasca was swamped with telegram messages from the Navy and Coast Guard regarding the loss as well; the radiomen were very likely overwhelmed with all of the traffic.
Hi Randy
Am I right in thinking that the microfilm records are records of official signals sent and received rather than the radio-room logs? And the radio-room logs were destroyed apart from the three pages preserved by Chief Bellarts?
Cheers
Colin
I've not seen the microfilm records; only the originals. And yes, radio room logs are available in the National Archives beyond what Bellarts saved in his donation to the Archives. The logs available are those in and around July 2, along with records from Howland Island. My understanding is that radio room logs were typically destroyed after each cruise, but at least from Itasca's POV, most of the telegrams sent back and forth were kept as copies. My databasing indicates which ship/organization received which message, so that if one particular ship did not retain it, that record exists so long as it was included in distribution. That's one of the reasons to database everything: if one ship/organization wanted to hide something, it would be hard to do so.
Quote from: Randy Jacobson on August 15, 2026, 08:47:19 PMThanks, Marty. I thought I had individual PDF's of the Itasca logs somewhere, but apparently not.
These are listed as logs:
- July 1 (http://tighar.org/Projects/Earhart/Archives/Research/JacobsonDatabase/RADIOLOG/RAD0701.PDF)
- July 2 (http://tighar.org/Projects/Earhart/Archives/Research/JacobsonDatabase/RADIOLOG/RAD0702.PDF)
- July 3 (http://tighar.org/Projects/Earhart/Archives/Research/JacobsonDatabase/RADIOLOG/RAD0703.PDF)
- Other (http://tighar.org/Projects/Earhart/Archives/Research/JacobsonDatabase/RADIOLOG/RADREST.PDF)
Quote from: Randy Jacobson on August 15, 2026, 08:47:19 PMBob Brandenburg also examined all of the post loss messages and signals and tried to determine the validity of them based upon radio propagation algorithms.
https://tighar.org/wiki/index.php?title=Robert_R._Brandenburg,_LCDR_USN_(ret)
- Harmony and Power: Could Betty Have Heard Earhart on a Harmonic? (http://tighar.org/Projects/Earhart/Archives/Research/ResearchPapers/Brandenburg/HarmonyandPower.pdf)
- Radio Direction Finder Analysis. (http://tighar.org/Projects/Earhart/Archives/Research/ResearchPapers/Brandenburg/RDFResearch/RDFAnalysis/RDFpaper.htm)
- The Radio Riddle. (http://tighar.org/Projects/Earhart/Archives/Research/ResearchPapers/Brandenburg/radioriddle.html)
- Post-Loss Signal Statistics with Tide Information. (http://tighar.org/Projects/Earhart/Archives/Research/ResearchPapers/Brandenburg/TidalStudy/TidalStudy.htm)
- Post Loss Radio Signals Technical Analysis. (http://tighar.org/Projects/Earhart/Archives/Research/ResearchPapers/Brandenburg/PLRSTechnical.html)
- WE-13C Transmitter Harmonic Power Output. (http://tighar.org/Projects/Earhart/Archives/Research/ResearchPapers/Brandenburg/WE-13.htm)
Hi Martin and Randy
Thanks for the links and endulging the whims of this newby. If a database could ever be described as epic this would be it!
Itasca maintained the radio watch until long after fuel exhaution and I am satisfied that there were no unreadable signals between 10:39 and 11:55Local.
I note the weather report sent by Itasca at 16:25L on the 2nd (Record 921) Surface wind: ESE 11, 1000ft: ESE 15 and 1900ft: ESE 16. This verifies my theory that the forecast wind (ENE) was wrong and the Electra was North of track.
It is interesting that Itasca was able to monitor the PBY transmissions between Hawaii and about 350nm North of Howland, I think I will finish by quoting a signal from the PBY:
20:03 APPROXIMATE POSITION LAT 0635 LONG 17200. LAST TWO HOURS IN EXTREMELY BAD WEATHER BETWEEN ALTITUDE 2000 AND 12000 FEET. SNOW, SLEET, RAIN, ELECTRICAL STORMS. IN DAYLIGHT CONDITIONS LOOK EQUALLY BAD. CLOUD TOPS APPEAR TO BE 18000 FEET OR MORE. AM RETURNING TO PEARLHARBOR NOW. HAVE 900 GALLONS FUEL ON BOARD. 07:10.
True heroes
Cheers
Colin
The PBY encountered the intertropical convergence zone, where high rainfall, winds, and thunderstorms reign. At that time of the year, it is typically 3-6 degrees above the equator. Trade winds north of the ITCZ are ENE; winds sound of the ITCZ are ESE. Nothing unusual in what was reported.
Quote from: Randy Jacobson on August 18, 2026, 07:45:39 AMThe PBY encountered the intertropical convergence zone, where high rainfall, winds, and thunderstorms reign. At that time of the year, it is typically 3-6 degrees above the equator. Trade winds north of the ITCZ are ENE; winds sound of the ITCZ are ESE. Nothing unusual in what was reported.
That is the point I made in my post
https://tighar.org/smf/index.php?topic=2238.0
All the more surprising that the forecast winds were wrong and that Noonan did not spot the mistake.