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Highlights From the Forum

October 29 through November 4, 2000
(page 2 of 3)

(click on the number to go directly to that message)
18 Re: Antenna and propagation simulation Hue Miller
19 Re: 150 SE by 50 E Tom King
20 Dashes? Edgard Engelman
21 Overnighters Dennis McGee
22 Position Reports Doug Brutlag
23 Celestial Choir Doug Brutlag
24 Re: W40K Bob Brandenburg
25 Re: Antenna and propagation simulation Bob Brandenburg
26 Question regarding wire in aircraft Mike Everette
27 Re: W40K Bob Brandenburg
28 Star (?) Witness: Lt. Lambrecht Ron Bright
29 All Ashore Followup Steve Gardetto
30 Re: W40K, New development Ric Gillespie
31 Manta Boards Frank Westlake
32 Re: Manta Boards Frank Westlake
33 Re: All Ashore Followup Tom King
34 Re: Antenna and Propagation Bob Brandenburg

Message: 18

Re: Antenna and propagation simulation

Date: 10/31/00
From: Hue Miller

By "down", I mean that output falls off precipitously. The same kind of electrical circuit that tunes your car radio to a station, tuned the output of the transmitter. (Although the transmitter was in fact broader tuning than a receiver).

I mean there’s not a lot of allowance for mistuning before operation becomes unacceptable. Your point about the distortion noted at Lae is right on. That -- knowing the modulation setup in the transmitter -- is a good sign that this channel was out of adjustment and power output also was down (to some unknown degree). Despite my forgetting that fact, I still maintain that this maladjustment would not favor harmonic power production. In fact, I even suggest if the transmitter was mistuned to some degree of diminished effectiveness on one channel, the harmonic power from that channel (2x, 3x....) would be diminished also.

Another interesting question that could be tested.

Hue Miller

Message: 19

Re: 150 SE by 50 E

Date: 10/31/00
From: Tom King

Could somebody fill me in on where "150 SOUTHEST by 50 EAST" came from? I must have missed it, and don’t see it anywhere in the Betty notebook.

LTM (who’s getting a little forgetful in her old age)

From Ric

It’s from a message heard by a short-wave listener by the name of Charles Russell in Dennison, OH at 03:31 EST on July 6. No frequency was mentioned.



What is interesting about this message is that it occurs during the same period when several hams heard something suspicious:


Corrected for time zones, this stuff is all going on at the same time.


Message: 20


Date: 10/31/00
From: Edgard Engelman

Some time ago there has been a vivid discussion on the forum about the presence of a Morse key connected to AE’s radio. The traditional position being that it was probably left back in the US.

However I went back today reading Itasca’s radio log on the web site and found this text:

ON 3105 -/ NRUI2 DE NRUI P AR 0800-3

Aboard Itasca: The ship can not give Earhart a "long count" on 7500 Kilocycles because its transmitter is incapable of sending voice on that frequency, but it does repeat the letter A in Morse code (dit dah, dit dah, dit dah), the prearranged signal for homing transmissions from Itasca. Earhart reports hearing the signal but is "unable to get minimum" and again asks Itasca to take a bearing on her. She sends long dashes on 3105.

So, my question:

How was she suppose to send the long dashes in absence of a key? The radio log does not suggest that she was pushing the ’push to talk’ button on the mike. What is your interpretation of this episode ?

From Ric

She had to either be using the push to talk or physically turning the transmitter off and on. The latter is what KGMB asked her to do to send dashes after she disappeared.

Message: 21


Date: 10/31/00
From: Dennis McGee

Steve Gardetto writes:

>Is there work that can productively and safely be done by a small
>onshore group in the available light between the time when the "commute
>boat" normally departs and sundown/sun-up?

Drawing upon my experiences on three TIGHAR expeditions in the north Maine woods looking for Coil’s and Nungesser’s "White Bird," I think the "overnighter" idea on Niku is a stretch.

On my first Maine expedition TIGHAR set up camp in the woods near our proposed search area precisely so we COULD get an early start and work late. It was a good idea but it had its draw backs, primarily we had a tendency to work TOO hard and it didn’t allow enough downtime for the crew. Plus preparing and provisioning a hardy breakfast, a stick-to-the-ribs lunch and a strappingly delicious dinner each day for 15-20 people put a big strain on our chief cook and quartermaster, Pat Thrasher, AKA Mrs. TIGHAR.

And even though we usually got up with sun, we didn’t hit the trail until about 8 a.m. or so, and then knocked off around 4 -5 p.m. Living in the wood is a lot different than camping in the woods, especially if you are not accustomed to it. It sounds the same, but there are big differences. And after dinner bell many of us were too pooped to pop. There was not much sitting around the camp fire until the wee hours singing camp songs. Generally, most of us were in our sleeping bags by 9-9:30 p.m. Luckily, the expeditions were during the two weeks in July of the off season for horse flies and Noseeums so we didn’t have to contend with those problems.

On the last two expeditions, we stayed in town and commuted daily to the search area. Yes, the work days were shorter but the crew was also better rested and more alert, which allowed us to work more efficiently and contributed to overall safety. And we ate at a local restaurant and packed in our lunches, so we got to use all of our people for searching and not using them for the care and feeding of the crew.

Being on Niku in that heat and humidity for 32-34 hours would be very stressful I would think. Going back to the ship to sleep and rest in an air conditioned cabin (or at least a cabin with a fan) would ease that stress.

In Maine, we also had to put up with the weather, which I found offensive! :-) I was lucky enough to pitch my sleeping bag under the only hole in a 20-man tent on the only night it rained. But the food was good.

LTM, who dislikes sleeping in wet beds
Dennis O. McGee #0149EC

From Ric

I have generally resisted suggestions that members of the team camp on the island for many of the same reasons Dennis describes. I recognize that there is a big romantic attraction to the idea among some team members and I’m willing to humor that as long as the weather remains good, but I really don’t think that we gain anything by it except less bitching.

Message: 22

Position Reports

Date: 10/31/00
From: Doug Brutlag

For Randy J.

I discovered the same thing you did about AE’s nebulous position reports. Without an accurate time over fix the report is a waste of airtime & breath. Not only sad...STUPID!

When FN was navigating for Pan Am on the China Clippers, standard PA procedure called for regular position reports every half hour which gave Lat/Long, altitude, speed, wind direction/velocity, ground speed, met report. In addition, the Clippers were given position reports of ships along the route, also on the half hour who could assist in case of emergency.

I was going to look at the route in detail by means of universal plotting charts, along with position reports, see how the flight may have progressed and possibly form an opinion if Fred aimed dead on for Howland or flew a deliberate offset, but without timely & accurate position reporting information it can’t be done.

Ric, did any of the investigators in 1937 ever comment on the lack of position reporting information and its contribution to AE’s demise?

I still regard FN as a master navigator. However I wonder why he didn’t see this coming and walk away from a publicity stunt that eventually took his life.

Doug Brutlag #2335

From Ric

The report filed by the captain of the Itasca was so scathing about just this issue that the Treasury Department was very hesitant to release it because of the damage it would do to Earhart’s reputation. Hence the infamous Morgenthau transcript (see Forum FAQs, Alternative Theories, #5).

Message: 23

Celestial Choir

Date: 11/1/00
From: Doug Brutlag

As sergeant-at-arms of the new leaner & meaner Earhart Forum, would you consider the idea of those interested members of the celestial choir trying a research experiment?

I’ve made a chart of the area from Howland to the Phoenix group showing locations of the land masses (islands) using exact latitude/longitude coordinates. It is on 2 pieces of paper each 12″ x 14″. When butted up together you have a custom made chart for the geographical area showing the land masses & lines of lat/long. To the sailors & navigators in your group, it is simply the VP-OS sheets otherwise known as universal plotting charts. With this projection one can plot LOPs in great detail & simulate some precise dead reckoning if desired.

How about those interested parties who know something about navigation (celestial preferred but not required) each take a copy of the sheet(s), run some calcs & estimates as they wish and let’s see what comes up. Might put this LOP question to rest. I’ll send out copies to choir members on request and one to TIGHAR if you’d like to put it on the website for others.

Doug Brutlag(who prefers not to have to dodge swings of bowie knives & pirate cutlasses)

Message: 24

Re: W40K

Date: 11/1/00
From: Bob Brandenburg

Warren Lambing writes:

> Is there anyway to ascertain, where the Ham operator in Wyoming may have
> been? Might be of interest to see if he could be in the same GC.
> From Ric
> How about 1408 Tenth Street, Rock Springs, WY? (Ron Bright has been in touch
> with the local paper.)

The great circle bearing (GCB) from Lake Worth Florida (W4OK) to Rock Springs is 309.6 degrees. The GCB from St. Petersburg to Rock Springs is 310 degrees. So those three sites are virtually on the same great circle. But the great circle containing Niku and Rock Springs does not include St. Petersburg or Lake Worth.

This raises new questions, as if we didn’t have enough already:

Did Rock Springs hear Earhart and relay the intercept live to W4OK? Did Betty hear the relay and W4OK being called by or responding to Rock Springs?

This gets curiouser and curiouser.

Bob Brandenburg, #2286

From Ric

"Rock Springs" is Dana Randolph, a 16 year old "amateur radio fan" with an "inexpensive commercial set." He ain’t relaying nothin’ to nobody. Dana is also an African-American in a town that has a black population of .01 percent. The fact that he was investigated and that the authorities agreed that the message he heard was "thought to be from KHAQQ" indicates to me that his report is highly credible.

So far in my plotting of reported post-loss signals I can tell you that at the time Dana is reported to have heard what he heard (15:00Z on July 4), Coast Guard San Francisco is hearing nothing on 3105 but within 15 minutes (at 15:15Z) Pan Am Mokapu in Hawaii takes a "doubtful" bearing of 213 degrees on a rough carrier on 3105. A 213 degree bearing from Mokapu passes very close to Gardner Island. The reported time of Dana’s signal is fairly shaky (a Honolulu Star Bulletin article that has his name as Charles and his age as 12) so it may be that PAA and Dana are hearing the same transmission except that PAA is hearing the badly degraded primary frequency while Dana is hearing intelligible voice on a harmonic.

Message: 25

Re: Antenna and propagation simulation

Date: 11/1/00
From: Bob Brandenburg

For th’ WOMBAT:

>Another quick question from WOMBAT. What effect would "ground" have on
>propagation of the Electra’s radio signal and also on reception?

When a transmitter antenna is in proximity to ground, the radiated field at a distance from the antenna is the resultant of a wave radiated directly from the antenna and a phase-reversed wave reflected from ground. The ground-reflected component is computed by the "method of images", in which the ground is replaced by an image of the antenna at a distance H below the ground plane, where H is the height of the real antenna above the ground plane. Because of this image relationship, the conductivity of the ground is a determinant in the strength of the radiated field. Clearly, a perfectly conducting ground is the ideal case, more about which later.

According to the reciprocity principle, a receiving antenna has the same image relationship with ground as does a transmitter antenna except, of course, that the incoming wave induces current in the receiving antenna - - in contrast to the transmitter antenna in which current generates the outgoing wave.

By driving a copper pipe into the ground (I use a length of steel concrete reinforcing rod - - works well for SWL), or connecting to a water pipe, you put the ground reference (the chassis) of the equipment, transmitter or receiver, at the same electrical potential as actual ground, thus getting maximum benefit from the image effect.

The fuselage of the Electra was the ground for the dorsal vee antenna and, being aluminum, was close to a perfect conductor. So the antenna had a virtually ideal ground whether airborne or on the ground. Water on the reef flat contacting the metal parts of the aircraft’s undercarriage had little if any effect on the performance of the antenna - - the ground that it "saw" was the fuselage. On the other hand, if the Electra had been made of non-conducting materials - - say, a wooden frame covered by fabric - - then the dorsal vee antenna would have behaved as if in "free space" when the aircraft was in flight, and would have behaved like an antenna close to ground when on the reef flat.

LTM, who says ground is good.
Bob #2286

Message: 26

Question regarding wire in aircraft

Date: 11/1/00
From: Mike Everette

I have a question relating to aircraft/airframe wiring practice in the 30s.

Does anyone know whether solid-conductor wire was ever used in wiring harnesses? (I am referring to gauges from around 18 to 30.)

Seems at first glance that stranded conductor would have been preferred due to less breakage under strain and vibration.

What type insulation was used? Probably cloth covered, but was it multilayer, as in scc or cc type? ("Single cotton covered" or "double cotton covered") I have seen a/c wire samples from the 40s which are, universally, stranded; and the cloth insulation may have a cotton "filament" running the length of the wire, separate from the jacket, wrapped around the conductor... this could often get in the way of soldering operations if not carefully stripped.

These samples are usually cotton (?) insulated with a woven outer jacket, which may be a solid color (usually white) or marked in some way, perhaps with a color tracer thread.

The scc and dcc wire I referred to earlier was, I know, common in radio construction. Many specs for "home brew" radio projects of the time called for coils to be wound with scc or dcc wire, and it was also used for hookup wire before plastic-insulated products came along... but, was this stuff ever used in aircraft wiring?

LTM (who wraps everything real securely to keep bugs out) and
Mike E.

Message: 27

Re: W40K

Date: 11/2/00
From: Bob Brandenburg

Ric wrote:

> "Rock Springs" is Dana Randolph, a 16 year old "amateur radio fan" with an
> "inexpensive commercial set." He ain’t relaying nothin’ to nobody. Dana is
> also an African-American in a town that has a black population of .01
> percent. The fact that he was investigated and that the authorities agreed
> that the message he heard was "thought to be from KHAQQ" indicates to me
> that his report is highly credible.
> So far in my plotting of reported post-loss signals I can tell you that at
> the time Dana is reported to have heard what he heard (15:00Z on July 4),
> Coast Guard San Francisco is hearing nothing on 3105 but within 15 minutes
> (at 15:15Z) Pan Am Mokapu in Hawaii takes a "doubtful" bearing of 213 degrees
> on a rough carrier on 3105. A 213 degree bearing from Mokapu passes very
> close to Gardner Island. The reported time of Dana’s signal is fairly shaky
> (a Honolulu Star Bulletin article that has his name as Charles and his age as
> 12) so it may be that PAA and Dana are hearing the same transmission except
> that PAA is hearing the badly degraded primary frequency while Dana is
> hearing intelligible voice on a harmonic.

Your mentioning the shaky 213 degree bearing reminds me that some time ago I looked into that case, using large scale topographic charts. I was curious because the Mokapu site is on the northeast side of the Koolau mountain range that runs parallel to the northeast shore of Oahu. In particular, I was wondering if the mountains could affect the bearing accuracy. They would if the signal arrival angle was low enough, but not if it was high enough so that Mokapu wasn’t in the RF shadow of the mountains. The vertical arrival angle of that signal from Gardner was about 1 degree. But the optical angle from Mokapu to the ridge crest, on the bearing of Gardner, is about 6 degrees. So it seems clear that the signal heard at Mokapu was "spilling" over the Koolau ridge en route to Mokapu. The geometry of the path and the ridge alignment is such that a signal arriving at an angle below the optical horizon of Mokapu would be skewed clockwise as it spills over the ridge, and also would be substantially dissipated. That could account for the "shaky" character of the bearing. It’s worth noting that the signal heard by Mokapu on 213 degrees could have originated from a source on a more southerly bearing - - not necessarily from a land source, perhaps a commercial aircraft operating between Oahu and Hawaii, or other islands to the south of Oahu. This doesn’t mean it couldn’t have originated at Gardner - - just something to keep in mind when evaluating possibilities.

And, before anyone asks - - no, I haven’t been withholding information. The 213 bearing issue wasn’t salient at the time, and so I just didn’t mention it. Given the recent new line of inquiry, it seemed pertinent to mention it now.

Bob #2286

Message: 28

Star (?) Witness/Lt. Lambrecht

Date: 11/2/00
From: Ron Bright

I’ll bat cleanup.

Lt Lambrecht’s flight on 9 Jul over Niku has been well documented. Weather clear, visibility excellent, could see a life raft at "5 miles", tramp steamer broken in two, etc. But a few questions remain.

It is almost inconceivable that GP or the Navy Department would not have initiated an additional explanation and interview with Lt Lambrecht and his observer after reading that "signs of recent habitation" were clearly observed on Niku (place not described) just 7 days after Amelia’s loss- a place where not only GP but many other knowledgeable officials thought she might have ended up. And a place that may have been transmitting post loss signals that Lt. Lambrecht would have been informed.

Lt Lambrecht clearly differentiated "previous habitation" seen earlier that day at McKean with the "recent" habitation signs at Niku. He zoomed and circled but "took it for granted" that no one was there. (TIGHAR argues he missed her and the plane) It sounds like everyone just took his report of 16 July for face value and never pursued a better explanation.


1. Was Lambrecht ever re interviewed sometime later re his definition, location and description of "signs"? (Sort of ala Bevington) Any record thereof?

2. Since Lambrecht is deceased has anyone ever pursued his relatives for any "oral history", dairy, memoirs, writings, etc., re his observation on Niku that fateful day of 9 July 1937. It may be that his possible "oversight" haunted him down the line.

"Signs of recent habitation" and "bivouacked" must be the most ambiguous words in the English language; E.B. White would roll over in his grave.

Ron Bright

From Ric

We talk about Lambrecht’s "report" but it wasn’t a report. It was an article written for the weekly newsletter of the Navy’s Bureau of Aeronautics and only other naval aviators probably ever saw it. The official report of the aerial search was written by the Colorado’s captain, Wilhelm Friedell, who said that no signs of habitation were seen on Gardner (directly contradicting the guy who was actually there).

Goerner interviewed Lambrecht sometime in the late ’60s, early ’70s and said, in a letter to me, that when questioned about what he had seen on Gardner he said only that he had seen "markers of some kind." Second-hand anecdote, but it’s all that we have. I spoke with Lambrecht’s daughter at a U.S. Naval Institute seminar on the Earhart disappearance several years ago. She had nothing to add to the story.

Message: 29

All Ashore Followup

Date: 11/2/00
From: Steve Gardetto

Thanks for your explanatory comments about the expeditions. It was your response to someone else’s inquiry months ago that first interested me on this topic: namely, that of how you allocate the fixed resources of an expedition in deciding what to do and what not to do.

Both you and Dr. Tom King alluded to the poor weather on the ’97 expedition. I checked out the Website details of that visit ("Hell & High Water") but didn’t see mention of the 4 team members staying overnight. How did that come about and was it in fact impossible to retrieve these team members from the island?

In postings long ago, the habits of the native wildlife were discussed, specifically, their ability to carry off pieces of carrion, bones, etc. When Dr. King and the others were spending those unplanned nights ashore (are they thus qualified as "castaways"? -- if so, time for a new T-shirt slogan!), did they have any problems with nocturnal visits from the creepy-crawlies?

I also have a few more questions about expedition basics:

When the team arrives ashore on a typical morning, and the workgroups head off in different directions, do the groups keep in contact via some sort of radio, or is there only a pre-arranged regrouping time?

I’m guessing that to minimize the ship-to-shore transport of supplies, lunch is the only meal typically enjoyed on terra firma. Is the practice to meet somewhere on the island for a team feast, or does each group just break at its own convenience?

How many deployable boats does Nai’a carry? If just one, I can imagine that its care and well-being is high on everyone’s nightly prayers. If there’s more than one, are they of different sizes? Are they Zodiac-type inflatables or are they wood/fiberglass hard-shelled boats?

I recollect seeing an old Jacques Cousteau clip (who knows, maybe it was Sea Hunt or Flipper) in which a boat- - not Calypso- - towed divers underwater, who used a kind of flipper board apparatus to steer themselves, in an attempt to search a large, relatively shallow area. Given the desire to search underwater areas at Niku, does this approach sound feasible, or would it simply provide an entertaining twist for the local sharks in obtaining their daily meal?

Niku III wasn’t able to use the ultralight because of bad weather. Was it even taken off the ship, and if so, how difficult was that? Do you intend to try to use it again on Niku IIII?

LTM (who promises shorter posts in the future)
Steve G., TIGHAR # something or other

From Ric

>How did 4 team members staying overnight come about and was it in fact
>impossible to retrieve these team members from the island?

Nai’a’s crew had catered a special dinner on the beach (the only time that happened) and had brought ashore all kinds of food that had been prepared aboard ship. There were lots of leftovers. As we were getting ready to return to the ship we received word that the weather forecast for the next day was for significantly higher seas, and since it was already a near-death experience just getting on and off the island, I was resigned to losing a day or so riding out the worst of the weather aboard ship. It was at that point that 4 team members approached me with the prospect of staying on the island, using the leftovers from the dinner as provisions. The up-side was that some work would get done despite the bad weather. The down-side was that if I left people ashore we were committing ourselves to staying on station at Niku no matter how bad the weather got -- and nobody knew how bad it would get. We were, in effect, gambling that it would improve enough to let us get them off. I decided to take the gamble but I didn’t like it. In the end, it worked out okay. The next day was bad but the day after was better and we were able to resume normal operations. The "castaways" got some work done and very much enjoyed their two-night stay on the island, but ironically the people at risk were the ones on the ship. If I had it to do over again -- with similar weather considerations -- I would turn down the request. The little bit of additional work that got done was not worth the risk to the expedition. Letting people stay ashore in good, stable weather however is a different situation.

> did they have any problems with nocturnal visits from the
> creepy-crawlies?

I’m sure Tom King will be happy to answer that.

>When the team arrives ashore on a typical morning, and the workgroups head
>off in different directions, do the groups keep in contact via some sort of
>radio, or is there only a pre-arranged regrouping time?

We do keep in contact by radio but we don’t generally regroup for lunch unless we’re all working close by anyway. If one group will be on a different part of the island they take their lunch with them.

>I’m guessing that to minimize the ship-to-shore transport of supplies, lunch
>is the only meal typically enjoyed on terra firma. Is the practice to meet
>somewhere on the island for a team feast, or does each group just break at
>its own convenience?

No cooking, and MRE stands for Meals Rejected by Ethiopians. Nai’a makes up sandwiches and fruit and bags of chips and such. It’s generally brought ashore in a big cooler with some bottles of frozen water to help keep everything cool until lunchtime. The thawed but still-cold water is also welcome.

>How many deployable boats does Nai’a carry?

Usually she carries two "Naiads" which have rigid aluminum hulls and inflatable sides - best of both worlds. There’s a big one and a little one (I forget the exact lengths). We base the big one in the lagoon and use the little one to ferry to and from shore.

> who used a kind of flipper board apparatus to steer themselves,

Manta-boards. We used them to search part of the lagoon in ’97. Plan to use them again, towed behind a launch.

The ultra-light aircraft was never even completely assembled in ’97. It became obvious that the weather was far too bad to use it. Our research has now progressed to the point that we have no real need for aerial observation or searching.


Message: 30

Re: W40K--New Development

Date: 11/2/00
From: Ric Gillespie

We have an interesting development in the saga of Betty’s notebook.

You’ll recall that among the first notations Betty made was: "W40K Howland port or WOJ Howland port"

WOJ proved to be nothing, but W40K sounded like it might be a HAM call sign. Janet Whitney dug out the information that, in 1937, W40K was the call sign assigned to Francis G. Carroll of Fort Worth, Florida. Betty has never heard of Francis G. Carroll. Why was his call sign in her notebook as something that had been said by Amelia Earhart, if indeed that is what she had said?

The fact that Mr. Carroll, like Betty, lived in Florida seemed like an odd coincidence so Bob Brandenburg did some checking. He found that a Great Circle from Gardner Island to St. Petersburg, if extended, also passes through Lake Worth (and nearby Palm Beach where, it turns out, Mr. Carroll actually lived in July 1937). In other words, if Betty could hear signals it is also likely that Mr. Carroll could (theoretically) hear signals, but Carroll -- unlike Betty -- could also transmit and (again theoretically) establish two way communication. If that had happened it could explain why Earhart had said his call sign.

Harry Poole did some checking and found that, wouldn’t you know it?, both Francis and his wife Leona died just this year and had been living in the Ft. Pierce area. TIGHAR member Terry Linley (who also happens to be my cousin) lives in Ft. Pierce and volunteered to try to find the only surviving child, Nancy. Her search was quickly successful and she discovered that Nancy Carroll, a retired Marine Corps major, lives just down the road. Francis Carroll had worked for a local radio station and was an avid HAM. Nancy couldn’t recall her father ever mentioning Amelia Earhart but Nancy’s housemate "Smitty" (also a retired Marine) recalled that some years ago (between 1987 and 1992) while watching a television documentary about Amelia Earhart, Nancy’s father had remarked " "I talked to her; I wondered what happened". Nancy didn’t hear the comment and Smitty dismissed it as an old man’s ramblings.

Nancy feels quite sure that she has her father’s HAM logs somewhere among his personal belongings and is now eager to help us verify whether or not her father may have, in fact, "worked" Amelia Earhart after she disappeared.

Of course, a thousand questions come to mind about what may have happened and why nothing was ever done about it -- but let’s take it one step at a time. Terry is working with Nancy to locate the logs.


Message: 31

Manta boards

Date: 11/2/00
From: Frank Westlake

Ric wrote:

> Manta-boards. We used them to search part of the lagoon in ’97.
> Plan to use them again, towed behind a launch.

I wouldn’t recommend it, not while breathing compressed air anyway. The danger of arterial gas-embolism is too great and you are too far from a recompression chamber. It’s deadly, especially in less than one atmosphere of pressure.

If it is necessary to tow a diver on SCUBA, the speed of the towing vessel should be less than the swimming speed of the diver. At such a slow speed it will be much more difficult for the diver to inadvertently bounce up. But I still don’t recommend towing a diver on SCUBA.

On snorkel there would be no danger of embolism.

Frank Westlake

From Ric

We’re not talking great depth (about 20 feet) or great speed here. The visibility on the lagoon bottom is sucko and you don’t want to get towed into a coral head. We’re using the boards primarily to save the divers the exertion of self propulsion.

But I’m not a diver. Any comments from experienced divers?

Message: 32

Re: manta boards

Date: 11/2/00
From: Frank Westlake

Ric wrote:

> We’re not talking great depth (about 20 feet) or great speed here.

That’s where the greatest danger is, the danger increases near the surface.

> But I’m not a diver. Any comments from experienced divers?

Sure. I agree with Frank. My experience is that of a Navy EOD diver. We would tow swimmers on snorkel, but never divers on SCUBA. If I remember correctly, most arterial gas embolism (AGE) cases experience death within the first ten minutes after surfacing. Many are dead before reaching the surface. In EOD, because of the type of work we do (did, I’m retired), we have the greatest number of AGE victims. And a particular unit I was in was at the top of the list. We had a chamber that was only 10 minutes away so we were fortunate to not have had any deaths though.

An experienced diver can be safely towed, but the danger still exists that the diver will become preoccupied and inadvertently ascend without exhaling. It only takes one or two feet in some cases. AGE needs to be treated IMMEDIATELY by recompression to 60 feet. It used to be 165 feet and some chambers may still use those old procedures. How long will it take you to get a diver to a chamber? Rhetorical, I’m sure it is much too long.

If you were doing this off the coast of a civilized area I would not be as concerned.

Frank Westlake

From Ric

Hmmm. I’m glad this came up (no pun intended).

Message: 33

Re: All Ashore Follow-Up

Date: 11/2/00
From: Tom King

Ric, I don’t want to be difficult, but -- hmm, how to put this diplomatically? Your version of our overnighter on Niku bears virtually no resemblance to my recollections. As far as I can recall, there was never any prospect that Nai’a would have to flee wildly before the storm, therefore putting those aboard at risk if she had to wait around for us; the only prospect was of a day or two lost work. We actually got quite a bit of work done in the time we were ashore, and just incidentally saved the GPS base station -- worth what, $40K or so? -- from being washed away, along with a fair amount of equipment on the lagoon shore. We observed conditions on the island that couldn’t otherwise have been observed, and that improves our perspectives on the dynamics of the place.

At the time you agreed to our remaining ashore, I was very pleased at what I thought was a dawn of collegiality -- a recognition that we are your adult, somewhat competent, colleagues, not 12-year old Cub Scouts who have to be kept in order lest we hurt ourselves. I’m sorry to see that I was in error.

As for creepy-crawlies, there were juvenile coconut crabs that rattled about all night in the pile of aluminum cans left over from the party. Since they were in their hermit phase, we wondered if any of them would trade their shells for Fiji Beer cans, but alas, none did. Once it got dark I went back and sat quietly in the midst of the village to see what it felt like -- and it certainly did FEEL creepy-crawly, but I can’t say that anything tangible assaulted me. Nevertheless I beat a hasty retreat back to the fire.

From Ric

As is no doubt abundantly clear to all, you and I have very different approaches to the conduct of expeditions. That will have to be resolved before we get on another boat together but this is not the place to do it.

Message: 34

Re: Antenna and propagation

Date: 11/2/00
From: Bob Brandenburg

For Vern:

> >The fuselage of the Electra was the ground for the dorsal vee antenna and,
> >being aluminum, was close to a perfect conductor. So the antenna had a
> >virtually ideal ground whether airborne or on the ground.
> And it was a pretty funny shaped ground plane, wasn’t it? The fuselage was
> pretty much under the part of the antenna near the apex of the "V" and very
> close. Further toward the tail, the fuselage is below and to the side of
> either leg of the "V" and still quite close but gradually getting more
> distant.

It surely was a funny shaped ground plane, and you have accurately described the situation. But it’s not the shape of the ground plane that matters, only the distance from the antenna to the ground plane.

> Who knows where the maximum current was in that strange shaped antenna for
> the fundamental frequency let alone possible harmonic frequencies?

The location of maximum current on the antenna, in and of itself, is not useful for evaluating the antenna. The key thing to know is the shape of the antenna radiation pattern, which includes its gain at any given azimuth and elevation angle.

The antenna model I use (see the 8th Edition) does a nice job of computing the 3-dimensional gain pattern for any antenna. The model does, however, assume a flat ground plane. To accommodate the model, I measured (using TIGHAR scale drawings) the 3-D distance from the antenna wire to the closest point on the fuselage at 2-foot intervals along the longitudinal axis of the airplane and computed the root-mean-square value over all distances, which I then used as antenna virtual height over a plane ground in the model. To check on the reasonableness of the resultant gain pattern calculations, I ran a second set of model computations in which I defined the antenna as a set of connected discrete wire segments where the endpoint heights of each segment were the corresponding 3-D distances from the fuselage surface. The resultant gain pattern computed by the model was not significantly different from that obtained in the first set of runs. Since the model gave me essentially the same results in both cases, I opted to stay with the simpler antenna characterization.

> Do we
> have any idea what the radiation pattern of such an antenna arrangement
> might be other than it would be pretty high angle radiation?

Yes. We have a complete 3-dimensional radiation pattern for the antenna at any frequency of interest - - I’m running the harmonic cases now - - at 1-degree resolution in azimuth and elevation. Actually, the radiation angle of interest in any given case is the launch angle for the ray bundle that propagates along the ionospheric path to the receiver. For example, in the case of the Betty intercept, the launch angle for a signal from Niku to St. Petersburg is about one degree. But at harmonic frequencies above 10 MHz, the launch angle is in the range of 10 to 15 degrees, depending on frequency. The propagation model (see the 8th Edition) uses the appropriate transmitter antenna gain for each case.

> That sort of
> "V" configuration was used a lot on airplanes. The radiation pattern must
> have been measured at some time.

It has indeed. There was some in-flight work done on a very similar vee configuration in 1938, to measure radiation resistance (see the 8th edition), which I have used to derive the radiation resistance of Earhart’s vee, so I could get to the radiation efficiency of the antenna. I’m not aware of any measurements of the radiation pattern.

Bob #2286

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