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Author Topic: Post-Loss Radio Signals  (Read 58065 times)

Ric Gillespie

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Re: Post-Loss Radio Signals
« Reply #30 on: October 25, 2011, 10:32:39 AM »

But, using your sign convention, Gardner should be -12.

What do you mean by "sign convention?"  Colorado, Swan, and Pelican all used -11 for the longitude of Gardner.  That's what we used.
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richie conroy

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Re: Post-Loss Radio Signals
« Reply #31 on: October 25, 2011, 11:24:48 AM »

http://www.nytimes.com/specials/magazine4/articles/earhart1.html

Amateurs Pick Up Signals

LOS ANGELES, July 2 (AP) -- Two amateur radio operators claimed to have picked up signals tonight on frequencies officially assigned to the plane of Amelia Earhart.

Walter McMenamy said he picked up weak signals on 6210 kilocycles at 6 P.M. (10 P.M. Eastern daylight time) and heard the letters "L-a-t" which he took to mean latitude. The letters were followed by indecipherable figures. The signals continued for some time. Mr. McMenamy expressed belief they came from a portable transmitter. He received other signals from a Coast Guard boat, presumably the cutter Itasca, requesting listeners to "stand by and listen on all frequencies."

At 8 P.M. (midnight Eastern daylight time), Carl Pierson, chief engineer of the Paterson Radio Corporation, picked up similarly weak signals on 3105 kilocycles, Miss Earhart's daytime frequency. He said they were erratic and indecipherable.

Both Mr. McMenamy and Mr. Pierson said the signals came from a hand-cranked generator. Miss Earhart carried one in her plane.

would a hand-cranked generator be enough to run radio ?
We are an echo of the past


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Gary LaPook

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Re: Post-Loss Radio Signals
« Reply #32 on: October 25, 2011, 11:25:35 AM »

But, using your sign convention, Gardner should be -12.

What do you mean by "sign convention?"  Colorado, Swan, and Pelican all used -11 for the longitude of Gardner.  That's what we used.

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The Navy regulation in force since 1920 required that their ships maintain standard zone times but provided exceptions when it was operationally convenient to use a different, non-standard, offset from Zulu time. The standard correction factors for converting one time to another used by navigators and, by regulation, the Navy is to use the sign that will convert local time to Zulu time, this is called the "Zone Description" (Z.D.) and must be recorded in the log book and next to the clocks. Itasca kept their clock set to 11:30 slow on Zulu so to convert Itasca time to Zulu their Z.D. was +11.30. Other users however see the problem in the reverse sense and use a correction factor that will convert Zulu time to local time so they would call to correction factor for Itasca time as -11:30 which added to Zulu time will produce the local time kept on Itasca. That is what I meant by the different "sign conventions." Either method will work as long as you keep it straight and don't get confused.

The standard time zone that is 12 hours slow on Zulu time extends from longitude 172° 30' west longitude to the 180th meridian. Gardner is located at 174° 32' west longitude so falls squarely within this time zone as does Howland. The Z.D., therefore, for Gardner is +12 hours (and for those going the other way, -12 hours.) Apparently for operational convenience, such as maneuvering in an area where you might cross back and forth across the dividing line between two time zones or to coordinate between ships that may be close to each other but on different sides of the dividing line, the ships you mentioned decided to keep their clocks set to Z.D. + 11 hours. But this doesn't change the fact that the standard time on Gardner (if someone were there) would have been 12 hours slow on Zulu in 1937. Since you purpose was to allow your readers to have sense of the actual time on Gardner, using the non-standard time kept on those ships instead of the correct time at Gardner will cause a one hour error and noon will happen at 13:00 instead of 12:00, sunrise will be at 7:00 a.m. and sunset at 7:00 p.m. (instead of 6 a.m. and 6 p.m.) and will  not be symmetrical around noon and this will also affect the local time for the tides which might be significant for the operation of the radios in the plane sitting on the reef.

We have seen that the Itasca, using the authority of the Navy regulation, set their clocks to a non-standard offset from Zulu, for their convenience, and did not maintain their clocks on the standard time zone in the vicinity of Howland which is 12 hours slow on Zulu, these other ships were doing the same thing.

gl
« Last Edit: October 25, 2011, 11:42:06 AM by Gary LaPook »
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Sheila Shigley

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Re: Post-Loss Radio Signals
« Reply #33 on: October 25, 2011, 11:39:29 AM »

The Navy regulation in force since 1920 required that their ships maintain standard zone times but provided exceptions when it was operationally convenient to use a different, non-standard, offset from Zulu time. The standard correction factors for converting one time to another used by navigators and, by regulation, the Navy is to use the sign that will convert local time to Zulu time, this is called the "Zone Description" (Z.D.) and must be recorded in the log book and next to the clocks. Itasca kept their clock set to 11:30 slow on Zulu so to convert Itasca time to Zulu their Z.D. was +11.30. Other users however see the problem in the reverse sense and use a correction factor that will convert Zulu time to local time so they would call to correction factor for Itasca time as -11:30 which added to Zulu time will produce the local time kept on Itasca. That is what I meant by the different "sign conventions." Either method will work as long as you keep it straight and don't get confused.

Ah, okay.  I think the term "offset" generates confusion, too, since it implies (to my brain) "offset from Zulu."  So a "-11" could either mean "Zulu -11 = local," or "local -11 = Zulu," correct?

And in 1937, Howland time was still different from Gardner/Niku time, correct?
« Last Edit: October 25, 2011, 11:43:10 AM by Sheila Shigley »
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Ric Gillespie

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Re: Post-Loss Radio Signals
« Reply #34 on: October 25, 2011, 11:54:26 AM »

You keep citing regulations and I'll keep citing reality.  The ships' logs consistently used half hour time zones when they were underway, far from land or other ships.  Colorado, Swan and Pelican all used 11 hours when in the vicinity of Gardner's longitude.  Gardner may have been square in the middle of the standard 12 hour Z.D. as you say but nobody seems to have used it.  We decided to use what was actually used because we want to stay within the context of the actual events as much as possible.  When you compile your own Post-Loss Radio Signals Catalog you can use 12 hours for local Gardner time if it makes you feel better.
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Sheila Shigley

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Re: Post-Loss Radio Signals
« Reply #35 on: October 25, 2011, 11:55:06 AM »

Maybe this view is better - 1936 map notes mention that this map shows:

• Time zone boundaries and clocks showing the time when it is midnight at Greenwich

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Ric Gillespie

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Re: Post-Loss Radio Signals
« Reply #36 on: October 25, 2011, 12:02:40 PM »

And in 1937, Howland and Gardner were still in different time zones, correct?

According to Gary, Howland and Gardner were officially both in the 12 hour time zone.  That's fine, but none of the ships used it. 
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Ric Gillespie

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Re: Post-Loss Radio Signals
« Reply #37 on: October 25, 2011, 12:08:43 PM »

would a hand-cranked generator be enough to run radio ?

There was no hand-cranked generator.  McMenamy and Pierson were hoaxers.  It's in the catalog.
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Sheila Shigley

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Re: Post-Loss Radio Signals
« Reply #38 on: October 25, 2011, 12:19:04 PM »

And in 1937, Howland and Gardner were still in different time zones, correct?

According to Gary, Howland and Gardner were officially both in the 12 hour time zone.  That's fine, but none of the ships used it.

Oops - I'd better qualify that - for our purposes both Howland and Gardner are -11 offset from Zulu, meaning 11 hours behind Zulu, correct?  Zulu -11 = Howland local, and Zulu -11 = Gardner local?
« Last Edit: October 25, 2011, 12:20:41 PM by Sheila Shigley »
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Ric Gillespie

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Re: Post-Loss Radio Signals
« Reply #39 on: October 25, 2011, 12:23:21 PM »

Oops - I'd better qualify that - for our purposes both Howland and Gardner are -11 offset from Zulu, meaning 11 hours behind Zulu, correct?  Zulu -11 = Howland, and Zulu -11 = Gardner?

For the purposes of TIGHAR's Post-Loss Radio Signals Catalog we have used 11.5 behind Zulu for Howland (because that's what Itasca was using) and 11 hours behind Zulu for Gardner (because that's what the Navy most often used for that longitude).
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Gary LaPook

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Re: Post-Loss Radio Signals
« Reply #40 on: October 25, 2011, 12:30:04 PM »

And in 1937, Howland and Gardner were still in different time zones, correct?

According to Gary, Howland and Gardner were officially both in the 12 hour time zone.  That's fine, but none of the ships used it.
--------------------------------------------
That's fine but you stated your purpose was to let the reader know what the castaways would observe on Gardner, not what the sailors on ships operating in the vicinity would observe. Either you should not call it "Gardner time" or you  should include a warning:

"WARNING, WHAT WE HAVE LISTED AS 'GARDNER TIME' IS ACTUALLY NOT WHAT WOULD HAVE BEEN OBSERVED ON GARDNER. IT IS ACTUALLY THE TIME OBSERVED ON NAVY SHIPS PARTICIPATING IN THE SEARCH AND IS ACTUALLY AN HOUR FAST ON WHAT WOULD HAVE BEEN OBSERVED BY EARHART AND NOONAN"

gl
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Sheila Shigley

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Re: Post-Loss Radio Signals
« Reply #41 on: October 25, 2011, 12:33:59 PM »

For the purposes of TIGHAR's Post-Loss Radio Signals Catalog we have used 11.5 behind Zulu for Howland (because that's what Itasca was using) and 11 hours behind Zulu for Gardner (because that's what the Navy most often used for that longitude).

Great - thank you!

Apparently the time zone intricacies wreaked some (extra) havoc during the war:

After GALVANIC was over and done...there was a very considerable amount of criticism from within the Navy raised over the inability of the landing boats to deliver Wave Four...on schedule.

The Sumner tide tables begin 15 January 1944. The ship's formula for high tide at Tarawa stated that, using zone+12 time, it occurred 2hrs 7min before high water at Apia, Samoa. The U.S. Coast and Geodetic Survey Tide Tables showed that this important event occurred (using zone-12 time) 3hrs 55 min before high water at Apia, Samoa. This is a sizeable variation in exact local times, even when the tide table of one day later is used.


http://www.ibiblio.org/hyperwar/USN/ACTC/actc-18.html
« Last Edit: October 25, 2011, 12:37:30 PM by Sheila Shigley »
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Gary LaPook

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Re: Post-Loss Radio Signals
« Reply #42 on: October 25, 2011, 12:38:47 PM »

Oops - I'd better qualify that - for our purposes both Howland and Gardner are -11 offset from Zulu, meaning 11 hours behind Zulu, correct?  Zulu -11 = Howland, and Zulu -11 = Gardner?

For the purposes of TIGHAR's Post-Loss Radio Signals Catalog we have used 11.5 behind Zulu for Howland (because that's what Itasca was using) and 11 hours behind Zulu for Gardner (because that's what the Navy most often used for that longitude).

But the radio log kept by the radio operators actually ashore on Howland used Z.D. +10:30 not + 11:30.

gl
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Ric Gillespie

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Re: Post-Loss Radio Signals
« Reply #43 on: October 25, 2011, 12:57:37 PM »

That's fine but you stated your purpose was to let the reader know what the castaways would observe on Gardner, not what the sailors on ships operating in the vicinity would observe.

That's not what I said.  I said, "We included the best available calculation of local time on Gardner in the 1937 context primarily to provide a sense of the time of day for the reader."  By "sense of time of day" I mean early morning, late morning, afternoon, evening, late at night, etc.  That's hard to get from Zulu time.

Either you should not call it "Gardner time" or you  should include a warning:

"WARNING, WHAT WE HAVE LISTED AS 'GARDNER TIME' IS ACTUALLY NOT WHAT WOULD HAVE BEEN OBSERVED ON GARDNER. IT IS ACTUALLY THE TIME OBSERVED ON NAVY SHIPS PARTICIPATING IN THE SEARCH AND IS ACTUALLY AN HOUR FAST ON WHAT WOULD HAVE BEEN OBSERVED BY EARHART AND NOONAN"

We don't know, and don't have any way of knowing, what local time Earhart and Noonan "observed" on Gardner - nor does it matter.  To include the statement you suggest would be to assert that we know something we can not possibly know. In historical writing "would have" is a guess masquerading as fact.  We have had this discussion before.  If you ever catch me pulling a "would have" jump all over me.  It's one of the most dangerous mistakes an investigator can make.

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Ric Gillespie

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Re: Post-Loss Radio Signals
« Reply #44 on: October 25, 2011, 01:00:55 PM »

But the radio log kept by the radio operators actually ashore on Howland used Z.D. +10:30 not + 11:30.

Sorry. I misspoke.  We use +11:30 for Itasca.  We use +10:30 for Howland for the reason you cite.
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