Tag Archives: Capt. Almon Gray

Conclusion of Gray’s “Amelia Earhart and Radio”: Former PAA flight officer’s findings still fascinate

In the conclusion of Almon Gray’s “Amelia Earhart and Radio,” the former Pan American Airways radio flight officer examines further technical and other aspects of Amelia Earhart’s final flight, including the origin and effectiveness of the radio direction finder on Howland Island, some of the possible post-flight radio transmissions that may have originated from the Earhart Electra, and Fred Noonan’s alleged drinking problem as it may have affected the flight.  As always, the real mystery is what transpired aboard the Electra in the hours before and after her last radio transmission, and the biggest question remains unanswered: Was Amelia actually attempting to reach Howland Island?  If she was, then Gray’s conclusions remain highly relevant today.

“Amelia Earhart and Radio,” Conclusion
By Almon Gray

THE HOWLAND ISLAND RADIO DIRECTION FINDER

Obviously Earhart had a misconception of the radio direction finder installed on Howland Island.  She apparently envisaged it as being a PAA type Adcock high frequency system, or its functional equivalent, which would take bearings on her 3105 kHz signals and send them to her just as the PAA station at Mokapu Point had done during her flight from Oakland to Honolulu.  Because of that she repeatedly asked Itasca to take bearings on 3105 kHz and transmitted signals upon which bearings were expected to be taken.  It appears that there may have been some justification for her having that concept.

When the decision was made to fly easterly around the world, and the long Lae-Howland leg was being studied, Earhart and Noonan suggested to the Coast Guard that a radio direction finder be set up on Howland (“PLANE SUGGESTS DIRECTION FINDER BE SET UP ON ISLAND, IF PRACTICABLE”).  According to the research of Capt. Laurance F. Safford, USN, it was at about this time that Mr. Richard B. Black, the Department of the Interior representative, who was to go to Howland in Itasca, conceived the idea of “borrowing” a so-called high frequency radio direction finder from the Navy to use on Howland Island.  Black advised G.P. Putnam, Earhart’s husband and business manager, of his plans and advised him when the gear had been obtained and put aboard Itasca.  No doubt Putnam passed this information along to Earhart.

It was on Howland Island that Black supervised construction of the air strip for Amelia Earhart’s scheduled refueling stop. Black was in the radioroom of the USCG Itasca as he listened to Earhart’s last known radio transmission indicating that she was low on fuel and was searching for Howland island.

Richard B. Black, the Interior Department representative who supervised construction of the Howland Island air strip for Amelia Earhart’s scheduled refueling stop.  Black was in the radio room of Itasca, as Earhart sent her last known radio transmissions.  As a lieutenant in the U.S. Naval Reserve in 1939, he was assigned as the U.S. Antarctic Service base commander, East Base, U.S. Antarctic Expedition.  In 1954, Black served as the base operations officer of the first U.S. Navy Deep Freeze expedition.

In a message sent June 27 to Commander, San Francisco Division, USCG, the C.O. Itasca [Cdr. Warner K. Thompson] reported on his readiness for supporting the upcoming flight.  One item was “DIRECTION FINDER INSTALLED ON HOWLAND.”  This fact was reported to Mr. Putnam, then in San Francisco, and he in turn passed the news to Earhart, who was then at Darwin, Australia. While the Itasca message did not specifically say “High Frequency Direction Finder,” there apparently had been sufficient other information, probably via telephone from Putnam, to cause Earhart to believe that it was such a device.  She likely assumed that the DF had been installed at Howland in response to the suggestion made earlier by Noonan and herself , and fully expected it to be a functional equivalent of a PAA-Adcock system.

According to Capt. Safford, who was in an excellent position to know, the direction finder station on Howland Island actually consisted of an aircraft type radio receiver and an aircraft type rotatable loop antenna which had been “hay-wired” together into a temporary DF installation.  It operated off storage batteries borrowed from Itasca.  The receiver and loop had been moon-light requisitioned(obtained by informal means) by Mr. Black and Lt. Daniel Cooper of the Army Air Corps, from a Navy patrol plane at Fleet Air Base, Pearl Harbor.

The equipment appears to have been a military version, or perhaps a twin, of the Bendix receiver and loop in the Earhart plane. At any rate, with a loop antenna, it certainly was not a high frequency direction finder and the probability of taking meaningful bearings with it on 3105 kHz over any significant distance, was practically nil. The Howland DF operator [Radioman 2nd Class Frank Cipriani] had only two opportunities to try taking a bearing on the plane, and in each case the plane’s transmission was so short that a really good attempt could not be made. Had the transmissions been sufficiently long the operator no doubt would have found that he could get no “minimum” and hence no bearing.

POST-FLIGHT SIGNALS

NAURU

On July 3 (GMT date) an operator at public service radio station VKT, Nauru, sent the following wire note” (an informal communication between operators) to RCA radio station KPH at San Francisco, with the request that it be passed to Itasca:

VOICE HEARD FAIRLY STRONG SIGS STRENGTH TO S3 [at] 0843 and 0854 GMT 48.31 METERS (i.e. 6216 kHz) SPEECH NOT INTERPRETED OWNING BAD MODULATION OR SPEAKER SHOUTING INTO MICROPHONE BUT VOICE SIMILAR TO THAT EMITTED FROM PLANE IN FLIGHT LAST NIGHT WITH EXCEPTION NO HUM ON PLANE IN BACKGROUND.”

Note that these signals were heard about 12-and-a-half hours after Itasca last heard the plane.

There is nothing that directly and positively connects these signals with the Earhart plane, however there is indirect evidence that warrants serious consideration:

(a) The frequency (6210 kHz) was right for it being the plane.  It was not a commonly used frequency in that area.

(b) The Nauru operator reported good signal strength and was able to judge the tone or timbre of the speaker’s voice yet was unable to understand what the speaker was saying.  He suggested the possibility of modulation problems.  The operator who had checked the plane at Lae and the DF operator at Howland who was trying to take a radio bearing on the plane, both had noted similar symptoms and suggested possible modulation problems.

(c) The probability of there being more than one transmitter in the area exhibiting the same symptoms of over-modulation on the same frequencies at essentially the same time is very small.

It is this writer’s opinion that the signals intercepted by Nauru were in fact from the Earhart plane no longer in flight.

Capt. Laurance Safford, the father of Navy cryptology, who established the Naval cryptologic organization after World War I and headed it, for the most part, though Pearl Harbor. Safford's verdict on the Earhart disaster was that the fliers "were the victims of her over-confidence, an inadequate fuel supply, bad weather, poor planning . . . miserable radio communications and probable friction between the crew." Did Safford know more about the fliers' fates than he ever publicly admitted?

Capt. Laurance Safford, the father of Navy cryptology, who established the naval cryptologic organization after World War I and headed it, for the most part, though Pearl Harbor.  Safford’s verdict on the Earhart disaster was that the fliers “were the victims of her over-confidence, an inadequate fuel supply, bad weather, poor planning . . . miserable radio communications and probable friction between the crew.”  Did Safford know more about the fliers’ fates than he ever publicly admitted?

PAN AMERICAN AIRWAYS

Shortly after the Earhart plane became overdue at Howland, the Coast Guard requested PAA to use its communication and radio direction finding facilities in the Pacific areas to assist in the search for the plane and survivors.  Instructions were immediately issued for the stations at Mokapu Point, Midway and Wake to monitor the plane’s frequencies as much as limited personnel would permit and be prepared to take radio bearings on any signals heard which might reasonably be believed to be coming from the plane.  A special radio circuit was set up to permit intercommunication among the three stations.  Numerous weak signals were heard but nothing of interest until 0948 July 5, GMT time and date.  The following is extracted from a report made by R.M. Hansen, the Radio Operator in Charge at the Wake Island station:

At 0948 a phone signal of good intensity and well modulated by a voice but wavering badly suddenly came on 3105 kc.  While the carrier frequency of this signal did not appear to vary appreciably, its strength did vary in an unusually erratic manner and at 0950, the carrier strength fell off to QSA 2 (2 on a scale of 0 to 5) with the wavering more noticeable than ever.  At 0952, it went off completely.  At 1212 (GMT July 5) I opened the DF guard on 3105 kc.  At 1223 a very unsteady voice modulated carrier was observed on 3105 kc approximately.  This transmission lasted until 1236 GMT.  I was able to get an approximate bearing of 144 degrees.  In spite of the extreme eccentricity of this signal during the entire length of the transmission, the splits were definite and pretty fair.

After I obtained the observed bearing, I advised Midway to listen for the signal (couldn’t raise Honolulu).  He apparently did not hear it.  This signal started in at a carrier strength of QSA5 (5 on a scale of 0 to 5) and at 1236, when the transmission stopped, it had gradually petered out to QSA2 during the intervals when it was audible.  The characteristics of this signal were identical with those of the signal heard the previous night (0948 GMT) except that at DF the complete periods of no signal occurred during shorter intervals.  While no identification call letters were distinguished in either case, I was positive at that time that this was KHAQQ [Earhart’s plane].  At this date I am still of this opinion.”

Midway heard a signal having the same characteristics, and almost certainly the same station, at 0638 GMT July 5.  A quick bearing of 201 degrees True was obtained, however the signal was not audible long enough to take a really good bearing and the 201 degree figure was labeled “approximate.”

Honolulu (Mokapu Point) also heard the “peculiar signal” on 3105 kHz several times.  From 1523 to 1530 GMT July 4 an attempt was made to take a bearing on it, however due to weakness and shifting of the signal, only a rough bearing could be obtained.  It was logged as 213 degrees, but it was implied that it was a doubtful bearing.  Sometime between 0630 and 1225 GMT another bearing was attempted on the peculiar signal.”  The log describes it thus: SIGNALS SO WEAK THAT IT WAS IMPOSSIBLE TO OBTAIN EVEN A FAIR CHECK. AVERAGE SEEMS TO BE AROUND 215 DEGREES — VERY DOUBTFUL BEARING.”  It is obvious that the bearings from Honolulu were greatly inferior to those taken from Wake and Midway and are useful mainly as indications that the unknown station continued to function.

Not much attention was paid to these interceptions at the time because no one was aware that Earhart’s radio signals had been abnormal.  Had it been known that she was having over-­ modulation problems more attention probably would have been given them because the Wavering in the carrier strength is consistent with a varying degree of over-modulation rapidly increasing and decreasing carrier power.  The gradual drop of signal strength from QSA5 to QSA2 over a span of 13 minutes is consistent with the further discharge of an already partially discharged storage battery power supply.  The peculiar signals on 3105 kHz heard by Wake, Midway and Honolulu may very well have come from the Earhart plane, and there is good reason to believe that the radio bearing taken on those signals by Wake was accurate within a degree or so.  The one from Midway may have had a somewhat larger error.

(Editor’s note: A number of radio operators, including several in the continental United States, reported hearing signals that they believed originated from Earhart and Noonan, and some have already been presented on this blog.  Please see  Earhart’s ‘post-loss’ messages’ Real or fantasy?  and Experts weigh in on Earhart’s ‘post-loss’ messages.)

FREDERICK J. NOONAN

There has been much speculation as to whether or not Fred Noonan could send and receive International Morse code.  From personal observation the writer knows that as of late 1935 Noonan could send and receive plain language at slow speeds, around eight to 10 words per minute.  Recent research by Noonan biographer Michael A. Lang has revealed that circa 1931 Noonan held a Second Class Commercial Radio Operator license issued by the Radio Division of the U.S. Department of Commerce.  Second Class licenses of that vintage certify that the holder has been examined and passed the following elements:

(a) Knowledge of the general principles of electricity and of the theory of radio­ telegraphy and radiotelephony.

(b) Adjustment, operation and care of apparatus.

(c) Transmitting and sound reading at a speed of not less than sixteen words a minute Continental Morse in code groups and twenty words a minute in plain language.

(d) Use and care of storage battery or other auxiliary.

(e) Knowledge of international regulations and Acts of Congress to regulate radio communications.

Perhaps the last photo taken before the flyers’ July 2 takeoff from Lae, New Guinea. Mr. F.C. Jacobs of the New Guinea Gold Mining Company stands between Amelia and Fred. Note that Fred looks chipper and ready to go, not hung over from a night of drinking, as has been alleged.

Perhaps the last photo taken before the flyers’ July 2 takeoff from Lae, New Guinea. Mr. F.C. Jacobs of the New Guinea Gold Mining Company stands between Amelia Earhart and Fred Noonan.  Note that Fred looks chipper and ready to go, not hung over from a night of drinking, as some have alleged.

Those writing about the Earhart disappearance have, in general, been very rough on Noonan because of his admitted problem with alcohol.  In some cases much rougher than was justified by the facts. For example in one book it is related that the night before the departure from Lae for Howland, Noonan went on a binge and did not get to the airfield until just before the plane was due to take off, and even then was so intoxicated that he had to be helped aboard the plane.  The implication being that he was largely responsible for the failure of the flight.  The official report of Guinea Airways Ltd., at Lae, made in response to a request from the U.S. Government, paints quite a different picture.  According to it the Lae wireless operator made attempts all throughout the day of June 30 to get time signals, requested by Earhart and Noonan, to permit Noonan to check his chronometer, but owing to local interference was unsuccessful that day.  That indicates that Noonan spent most of June 30 at the radio station.

At about this point, Earhart decided to take off for Howland Island at 9:30 a.m. on July 1, subject to obtaining the time signal.

At 6:35 a.m. July 1st Earhart took the plane up on a 30-minute test hop after which the tanks were topped off and she was ready to go, except that a time signal had not yet been obtained.  This day the difficulty was at the radio station which transmitted the signals.  Extraordinary steps were taken to get a time signal but when one had not been obtained by 10:50 a.m. Earhart decided to postpone her departure until the next day, July 2.  During the rest of the day constant watch was kept for the reception of time signals and finally at around 10:20 p.m. an excellent signal was received by Noonan which showed his chronometer to be three seconds slow.  Noonan obviously had spent most of that day at the radio station.

On July 2 at 8:00 a.m. another time signal was received, this one from Saigon, and the chronometer checked the same as the previous night.  Both Noonan and Earhart expressed their complete satisfaction and decided to leave at 10:00 a.m., which they did.

Only Noonan would have checked the chronometer, so the report seems to indicate clearly that Noonan was sober and in good shape at 8:00 a.m. and probably was that way when the plane took off.

CONCLUSIONS

From the standpoint of radio, Earhart’s decision to rely completely on radiotelephony, and her removal of the trailing antenna, showed poor judgment and introduced unnecessary and unjustifiable risks.  However it cannot be denied that she got as far as Lae without trouble with what she had.  It was her mistake in designating 7500 kHz as the homing frequency for Itasca that got her into deep trouble.  Even that difficulty probably could have been overcome had she been able to communicate with Itasca and agree on a suitable homing frequency.  Fate intervened, however, and something occurred in her receiving system which made it impossible for Earhart to hear any signals with her gear set up in the configuration she was accustomed to use for communications.

She did not understand the technical aspects of radio well enough to diagnose her problem and was not sufficiently familiar with the radio gear to know all the options available to her.  She had been taught to shift the receiver to the loop antenna when she wanted to take a bearing, but probably no one had ever explained to her how the loop also could be used in carrying on communications.  Had she been aware of that option and listened on the loop for Itasca‘s voice signals on 3105 kHz, no doubt she would have heard the ship and been able to establish two-way communications.

The probability is very high that the failure of the receiving system to receive signals when using the fixed antenna was due either to a defective feed line between the receiver unit and the send/receiverelay in the transmitter, or a defect in that relay itself.  The odds are about 95 to 5 that the relay was at fault.  It is considered therefore that a failure of that relay was the one single thing most responsible for the failure of the Earhart flight.

If it is assumed that the “peculiar signals” intercepted by Nauru and the PAA stations at Wake and Midway were in fact from the Earhart plane then the following may be deduced from the radio signals:

(a) The landing was fairly successful.  The plane did not nose over or break up, otherwise the radio could not have been used.

(b) The landing was not in the open sea.  Had it been, enough salt water would have seeped in to enter the wiring and disable the radio transmitting gear in a relatively short time.

(c) Earhart survived the landing.  She was heard by the Nauru operator long after the plane would have run out of gas.

(d) Noonan survived.  A man’s voice was distinctly heard on the “peculiar signal” by Midway.  It was unintelligible.

Almon Gray at Gray's Blue Harbor, Maine, home shortly before his death in September 1994. Gray, a Navy Reserve captain and Pan American Airways China Clipper flight officer, flew with Fred Noonan in the 1930s and was an important figure in the development of the Marshall Islands landing scenario. Bill Prymak, Amelia Earhart Society founder and president, called Gray's analysis of Earhart's radio problems "

Almon Gray at his Blue Harbor, Maine, home shortly before his death in September 1994. Gray, a Navy Reserve captain and Pan American Airways China Clipper flight officer, flew with Fred Noonan in the 1930s and was an important figure in the development of the Marshall Islands landing scenario.  Bill Prymak, Amelia Earhart Society founder and president, called Gray’s analysis of Earhart’s radio problems during her last flight “one of the finest pieces of work ever presented on this subject.”

(e) Either Earhart or Noonan, or both, were alive and with the plane at least until 0948 July 5, 1937 GCT time and date.  Thepeculiar signals were last heard then.

(f) The “peculiar signals” probably were coming from the eastern or southeastern part of the Marshall Islands.  (End of Almon Gray’s “Amelia Earhart and Radio.”)

Bill Prymak’s note:  Capt. Gray, USNR (Ret.) received his Commercial Radio Operator License in 1930, and went with Pan American in 1935, when they started the trans-Pacific service.  He became Flight Radio Officer on China Clipper type aircraft, and later was promoted to Assistant Superintendent of Communication in 1937.

The AMELIA EARHART SOCIETY finds the above radio analysis of the last flight to be one of the finest pieces of work ever presented on this subject.

Editor’s note: We should remember that in considering this analysis of Earhart’s final flight, Almon Gray took the position that the fliers were actually trying to reach Howland Island, and that all their actions were directed toward that goal.  If Amelia and Noonan were not trying to reach Howland, but were engaged in some sort of covert operation, which certainly cannot be ruled based on our limited knowledge of what transpired during those final hours, then many of Gray’s findings become largely irrelevant. 

Almon Gray’s “Amelia Earhart and Radio,” Part I

Almon Andrew Gray was a pioneer in aeronautical communications.  After graduating from the George Stevens Academy  in 1928 and the Massachusetts Radio Telegraph School in 1930, he enlisted in the Navy, where he was a radioman and gunner aboard cruiser-based aircraft.  He also learned to fly.

Upon expiration of his enlistment he signed on with Pan American Airways, and in 1935 helped build the bases to support the first trans-Pacific air service, and was first officer-in-charge of the PAA radio station on Wake Island.  After the San Francisco-Hong Kong air route was opened in late 1935, he was a radio officer in the China Clipper and her sister flying boats.  Later he was assistant superintendent of communications for PAA’s Pacific Division.  Gray was also a Navy Reserve captain, flew with Fred Noonan in the 1930s and was an important figure in the development of the Marshall Islands landing scenario.  He died at 84 on Sept. 26, 1994 at Blue Hill, Maine.  In coming weeks and months, some of Gray’s writings will be featured on this blog.

Capt. Almon Gray, USNR. wrote extensively on Amelia Earhart's radio problems during her last flight.

Capt. Almon Gray, USNR, wrote extensively on Amelia Earhart’s radio problems during her last flight.

More than anyone in Earhart research history, with the possible exception of Paul Rafford Jr., Almon Gray was qualified to discuss Amelia Earhart’s radio arrangements and behavior. “Amelia Earhart and Radio” first appeared in  the June 1993 issue of Bill Prymak’s Amelia Earhart Society Newsletters.

From the outset, readers should understand that in this analysis, Gray assumes that Earhart was actually trying to reach Howland island, and that she was attempting to establish two-way communication with Itasca, which never happened. In his piece, Gray also doesn’t try to explain why she was never on the air for more than 10 seconds, something that has led many to speculate that Earhart didn’t want her position to be known and that something else was afoot besides her official flight plan.  

AMELIA EARHART AND RADIO,” Part I of III

By Almon A. Gray

INTRODUCTION

Most of that written about the disappearance of Amelia Earhart while on an around-the-world flight in 1937 attributes her failure to reach Howland Island to unstated deficiencies related to radio.  It appears however that very little has been written about the nature of those deficiencies, or how they came about.  What follows will attempt to fill that gap and show what errors in planning and execution were made in respect to radio; what failure or malfunctioning of radio equipment occurred and the probable reason for it; and will point out the single item or event deemed most directly responsible for the failure of the plane to reach Howland Island.

Since 1937 the unit of measurement for radio frequencies had been changed from cyclesto hertz(Hz), consequently kilocycles (Kc) and kilohertz (kHz) will be used interchangeably, as will megacycles (Mc) and megahertz (MHz).  It is assumed that the reader already is familiar with the general history of the flight.

BACKGROUND

In early 1937, several weeks before her Oakland-Honolulu flight, and while she still intended to circumnavigate the world in a westerly direction, Miss Earhart met at Alameda, Calif., with George Angus, the superintendent of communications for the Pacific Division of Pan American Airways.  Angus was responsible for the radio communication and radio direction finding networks which supported the PAA clippers on their trans-Pacific crossings, and Miss Earhart wished to arrange for help from those facilities during her planned flight.  She was particularly interested in obtaining radio bearings to augment her celestial navigation.  At that time PAA had specially designed versions of the Adcock radio direction finding system in service at Alameda; Mokapu Point, Hawaii; Midway Island; Wake Island; Guam; and Manila, Philippines to support Clipper operations.

These systems were capable of taking radio bearings on frequencies much higher than could be utilized successfully by conventional loop-type direction finders, hence were effective over much greater distances.  They were commonly referred to as “high frequency DFs,” and were the only ones of that type in the United States and its territories.  Angus agreed to help Earhart while she was within radio range of PAA stations, and details for so doing were worked out.

This was somewhat complicated inasmuch as PAA was not equipped to transmit on either of Earhart’s communication frequencies (3105 kHz and 6210 kHz) and could not transmit voice on any frequency.  The solution agreed upon was that the plane would request a bearing by voice on the frequency in use (usually 3105 kHz at night, 6210 kHz during the day) and follow the request with a series of long dashes lasting in the aggregate a couple of minutes.  The PAA DF station would take a bearing and transmit it to the plane on a previously agreed upon PAA frequency, using CW(telegraphy) sent at such a slow speed that the individual dots and dashes of the numbers could be copied on paper and later translated into numbers.  This arrangement was tested on the flight from Oakland to Honolulu with the bearings being taken by PAA on 3105 kHz and sent to the plane on 2986 kHz.  It worked out very well.

The RA-1B was a brand new Bendix product and was reputed to be pushing the state of the art in aircraft receiver designed

The Bendix RA-1B, used in Amelia Earhart’s Electra during her final flight without apparent success, was a brand new product and was reputed to be pushing the state of the art in aircraft receiver design.

The Oakland-Honolulu flight was uneventful, and from the standpoint of radio was handled much the same as a Clipper flight.  Captain Harry Manning, an experienced radio operator, handled the Electra’s radio and DF gear while the ground radio facilities were operated by the regular PAA professional radio operators. Radio bearings were furnished the plane at frequent intervals, first from Alameda and later from Mokapu Point. They checked well with the positions Noonan determined by celestial navigation.  As the plane neared Oahu, Manning set up the plane’s direction finder to home on the Marine Radio Beacon (290 kHz.) at Mokapu Point (near Diamond Head) and Earhart homed in on it to a successful landfall.

During an attempted takeoff for Howland Island from Luke Field, near Honolulu, on March 20, 1937 the Electra ground-looped and was damaged to the extent that it was shipped back to the Lockheed plant in California for repairs.  There had been no major damage to the radio gear, and the main thing done to the radio system while at Lockheed was to replace the Western Electric Model 20B radio receiver and its remote control apparatus with a Bendix Type RA-1B Aircraft Radio Receiver and its accessories,which included means for complete remote control from the cockpit.  This work was done by Lockheed contract technician Joe Gurr.

 THE NEW RECEIVER

The RA-1B was a brand new Bendix product and was reputed to be pushing the state of the art in aircraft receiver design.  It was a super heterodyne, which had the frequency range .150-1.50 and 1.80-15.0 Megahertz, which was divided into six bands: I: .150 – .315; II: .315 – .680; III: .680- 1.50; IV: 1.80 – 3.70; V – 3.70 – 7.50; VI: 7.50 – 15.0.

The gap between 1.50 and 1.80 MHz was to accommodate the intermediate frequency. It could receive voice orCWsignals, and there was a three-position antenna selector switch which permitted three choices of antenna.  With the switch in theDFposition, the receiver was connected to the Bendix type MN-20 rotatable loop mounted atop the fuselage over the cockpit, and the combination comprised a radio direction finder.  With the switch in the TAposition the receiver was connected to the trailing antenna, and when in the FAposition it was connected to the fixed antenna.  It should be noted that signals from the loop antenna went directly from the loop, through the antenna switch, to the input of the receiver, whereas signals from the fixed or trailing antenna passed through the “send-receive” relay in the transmitter before going through the antenna switch to the receiver input.

It also should be noted that on this model receiver any radio signal within its overall frequency range could be received on the loop antenna.  Because of this, some people had the impression that radio bearings could be obtained on any frequency within the receiver’s frequency range, and the unit was sometimes spoken of as a “high frequency direction finder.”  The unit of course had no such high frequency direction finding capability, and in later models circuitry was introduced to limit reception on the loop antenna to only frequencies in that part of the overall range deemed suitable for radio direction finding with a loop antenna, i.e. below about 1.80 MHz.

A rare photo of Amelia Earhart and her Electra at the Burbank repair facility sometime during the spring of 1937.

A rare photo of Amelia Earhart (right) and her Electra 10E, NR 16020 at the Lockheed repair facility in Burbank, Calif., sometime during the spring of 1937.

THE RADIO SYSTEM

When the plane left the Lockheed plant after being repaired the radio system was comprised of the following elements:

(1) Bendix Type RA-1B Aircraft Radio Receiver.  Mounted in the cabin but having remote controls in the cockpit.

(1) Western Electric Model 13-C 50-watt Aircraft Transmitter.  It had three crystal-controlled channels, 500, 3105 and 6210 kHz and could be used for voice or CW (radiotelegraph) transmissions.  It was mounted in the cabin but there were remote controls in the cockpit.

(1) Bendix Type MN-20 rotatable shielded loop antenna.  It was mounted on the top of the fuselage over the cockpit, with the knob which rotated it located on the overhead of the cockpit, between the pilots.  It was used primarily for taking radio bearings but was useful as a receiving antenna under conditions of heavy precipitation static noise.

Provision for plugging in a microphone, headphones, and a telegraph key at each side of the cockpit.

A telegraph key and provision for plugging in headphones at the navigator’s table.

A 250-foot flexible wire trailing antenna on an electrically operated, remote-controlled reel, located at the rear of the plane.  The wire passed to the outside through an insulated bushing and had a lead weight, orfish, at the end to keep it from whipping when deployed.  There was a variable loading coil used in conjunction with this antenna to permit its use on 500 kHz.  This antenna was long enough to give excellent radiation efficiency on all three of the transmitting frequencies. 

A fixed antenna which was a wire Veewith its apex at a stub mast mounted on the top of the fuselage, about over the center section of the wing, and the two legs extending back to the two vertical fins.  This antenna was so short that its radiation efficiency was extremely low.  It was not intended to be used on 500 kHz and probably the radiated power on the other two frequencies was very low.  It was meant to be used mainly for local communications around an airport when it was not possible to have the trailing antenna deployed.  According to some accounts there was a second Vantenna mounted on the underside of the fuselage and connected in parallel with the top V antenna.  If so, it was removed or disconnected before the plane left Miami.

THE SECOND MISTAKE

Earhart flew the plane to Miami in the latter part of May 1937, and there made her second major error of judgment in respect to communications.  (The first was in deciding to rely completely on radiotelephone for her air-ground communications.)

One of the first things she did after arriving in Miami was to have the trailing antenna and associated gear completely removed.  John Ray, an Eastern Airlines technician, who had his own radio shop as a sideline, did the work.

This had a devastating impact both on her ability to communicate and on her ability to use radio navigation.  With only the very short fixed antenna remaining, virtually no energy could be radiated on 500 kHz.  This not only precluded her contacting ships and marine shore stations, but more importantly, it prevented ships (including the ITASCA) and marine shore direction finding stations from taking radio bearings on the plane, inasmuch as 500 kHz was the only one of her frequencies within the frequency range of the marine direction finders.  Thus any radio aid in locating Howland Island would have to be in the form of radio bearings taken by the plane on radio signals from the U.S. Coast Guard Cutter Itasca.

The shortness of the antenna also drastically reduced the power radiated on the two high frequencies. Paul Rafford Jr., an expert in this field, estimated that the radiated power on 3105 kHz was about one-half watt.  This obviously was a tremendous handicap in the high static level of the tropics.

The fixed antenna also may have been responsible for the distortion in Earhart’s transmitted signals reported by the operators at Lae, Howland and Nauru as seriously affecting the intelligibility of her voice transmissions.  (A mismatch between the antenna and the final amplifier of a WE-13C transmitter could cause the transmitter to over-modulate and thus introduce distortion.)

Despite the shortcomings of her radio system, Miss Earhart got as far as the Dutch East Indies without major incident.  There however, through lack of understanding, she made an error which ultimately lead to her failure to reach Howland Island.

Amelia with the loop radio direction finder

Amelia with the Bendix Type MN-20 rotatable shielded loop antenna, which was mounted on the top of the fuselage over the cockpit and apparently failed to help her in any significant ways during the final flight. 

THE THIRD MISTAKE

Three ships had been assigned to assist Earhart on the South Pacific over-water flights.  Itasca was at Howland Island, Ontario  about halfway between New Guinea and Howland, and Swan between Howland and Hawaii. One function of these vessels was to transmit radio signals upon which Earhart could take bearings with her radio direction finder and thus be helped with her navigation.  Suitable homing signals from Itasca were extremely important, in fact vital.  Should Noonan’s celestial navigation not hit Howland right on the nose, homing in on Itasca‘s signals with her DF was the only way Earhart could be sure of finding Howland before her fuel was exhausted.

In a message dated June 23, 1937 addressed to Earhart at Darwin or Bandung, Mr. Richard Black, aboard Itasca, advised her of the radio frequencies available aboard the Ontario, Swan and Itasca, and asked her to designate the frequency she wished each ship to use to provide homing signals for her.  The same day the Commanding Officer of Itasca requested that he be advised twelve hours prior to her departure from New Guinea of her desires in matter of radio, and warned her of the slowness of communication via Port Darwin.

Miss Earhart received these messages while she was at Bandung, Java, having work done on the plane.  On June 27, the day before she took off from Bandung for Koepang and Darwin, she sent the following response:

From: Earhart via RCA Manila & N-PM Navy Radio Honolulu
To: ITASCA (Black) June 27, 1937 (Java date: June 26, Howland)

SUGGEST ONTARIO STANDBY ON 400 KILOCYCLES TO TRANSMIT LETTER N FIVE MINUTES ON REQUEST WITH STATION CALL REPEATED TWICE END OF EVERY MINUTE STOP SWAN TRANSMIT VOICE NINE MEGACYCLES OR IF I UNABLE RECEIVE READY ON 900 KILOCYCLES STOP ITASCA TRANSMIT LETTER A POSITION OWN-CALL LETTERS AS ABOVE ON HALF HOUR 7.5 MEGACYCLES STOP POSITION SHIPS AND OUR LEAVING WILL DETERMINE BROADCASTING SPECIFICALLY STOP IF FREQUENCIES MENTIONED UNSUITABLE NIGHT WORK INFORM ME LAE STOP I WILL GIVE LONG CALL BY VOICE THREE ONE NAUGHT FIVE KCS QUARTER AFTER HOUR POSSIBLY QUARTER TO (signed) EARHART

A person experienced in radio direction finding would find that message very strange.  Why would Swan be asked to transmit homing signals on 900 kc, a frequency in the broadcast band, when a lower frequency in the aeronautical radio navigation band would be much better?  And why would Itasca be asked to send homing signals on 7.5 Mc when that frequency was so high that the possibility of getting useful bearings on it with the plane’s direction finder was nil?  Perhaps some of the personnel in Itasca had those questions but took the attitude “She is in the Flying Laboratory.  Who knows what hush-hush gear she has aboard?  If she wants 7.5 Mc, that is what she is going to get.”

No one questioned the message and Itasca tuned up its transmitter to send homing signals on 7.5 Mc.  What happened after that has been well covered in the media and in numerous books.  When the plane arrived at what Earhart believed to be the vicinity of Howland, no land could be found despite considerable visual searching, whereupon Earhart asked Itasca to send homing signals on 7.5 Mc, Itasca complied.  Earhart heard the signals but reported to Itasca that she was “unable to get a minimum” on them.  This meant she could not get a bearing on that frequency.  She then asked Itasca to take bearings on her 3105 kHz transmissions, apparently believing that the direction finder ashore on Holland Island could take bearings on that frequency just as the PAA Adcock systems had done on the earlier flight from Oakland to Honolulu.  When she heard no response from Itasca (the reason she did not hear any response will be addressed elsewhere) she transmitted her line of position, said they were running north and south and that she was shifting to 6210 kHz.  She was not heard again by Itasca.  Apparently she commenced execution of her Emergency Plan at about that point.

Because the unsuitability of the homing frequency used by Itasca had such an adverse impact upon the flight it seems appropriate to digress a bit here to try to find out:

(a) How was the plan for the use of radio homing beacons aboard the three ships developed?

(b) What was the plan?

(c) Did the message of June 27 from Earhart to Itasca (Black) accurately reflect the plan which had been developed?  If not, what were the differences and why had they been introduced? (End of Part I.)

In Part II of Amelia Earhart and Radio,” Almon Gray will continue to analyze Amelia Earhart’s radio communications during her doomed last flight.  He will also attempt to explain how and why Amelia’s transmissions were so completely ineffective, or at least appeared to be.

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