Direction finding - Revision history

Moleski: /* References */

2013-02-07T21:55:35Z

References

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	:: For the next thirty minutes everything was quiet, but then, exactly on the half hour, government radio operators in Hawaii heard dashes and a weak voice signal, this time on Earhart’s other frequency, 6210 kilocycles. It is not clear whether Coast Guard operators at the Hawaiian Station or army operators at Fort Shafter—or both—heard these signals. Dashes and voice heard together suggest that, once again, the transmissions were being sent using a microphone rather than a sending key. Itasca did not hear the signals; the ship’s radio operators were not listening on that frequency. Howland Island did not hear anything either; Cipriani was still recharging his batteries. There is, however, a report that someone else heard a voice at that moment. (118)		:: For the next thirty minutes everything was quiet, but then, exactly on the half hour, government radio operators in Hawaii heard dashes and a weak voice signal, this time on Earhart’s other frequency, 6210 kilocycles. It is not clear whether Coast Guard operators at the Hawaiian Station or army operators at Fort Shafter—or both—heard these signals. Dashes and voice heard together suggest that, once again, the transmissions were being sent using a microphone rather than a sending key. Itasca did not hear the signals; the ship’s radio operators were not listening on that frequency. Howland Island did not hear anything either; Cipriani was still recharging his batteries. There is, however, a report that someone else heard a voice at that moment. (118)

	~~== References ==~~
	~~<reference />~~

	== Bearings taken on transmissions after July 2 ==		== Bearings taken on transmissions after July 2 ==

Moleski: /* HFDF on Howland */

2013-02-07T21:55:19Z

HFDF on Howland

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	"According to Bellarts' later recollections, the HF/DF loaned to [[Black\|Dick Black]] and [[Cooper\|Lt. Dan Cooper]], and operated on Howland by Frank Ciprianni, was a primitive and poorly engineered device."<ref>[[Gillespie]] to EPAC, 26 May 2009.</ref>		"According to Bellarts' later recollections, the HF/DF loaned to [[Black\|Dick Black]] and [[Cooper\|Lt. Dan Cooper]], and operated on Howland by Frank Ciprianni, was a primitive and poorly engineered device."<ref>[[Gillespie]] to EPAC, 26 May 2009.</ref>

			:; Excerpts from ''[[Finding Amelia]]''

			:: On Howland Island, Cipriani heard the transmission as well, although he was “using the direction finder and receiver sparingly due to heavy drainage on batteries.”<ref>Howland Radio Log, 0747, July 3, 1937, p. 1.</ref> The signal Cipriani heard was strong. He rated it strength 4 (“good, readable”), but it was too short and obscured by too much static for him to get a bearing. (93)

			:: Galten immediately replied to Earhart’s call: “KHAQQ from Itasca. Your message okay. Please reply with voice.” Onshore, Cipriani heard Galten’s transmissions, but his batteries were now so weak that he had not been able to hear Earhart’s call, let alone take a bearing on her.<ref>''Itasca'', RLP2, raw version, 0749–50–57, July 2, 1937; Howland Radio Log, 0845, July 3, 1937.</ref> (96)

			:: Earhart sent long dashes on 3105 kilocycles while Galten tried to call Cipriani to alert him to the transmission. But it was no good. Cipriani was trying to conserve his weak batteries and heard only the tail end of Earhart’s transmission.<ref> Bellarts interview, April 11, 1973, pp. 84, 85; Howland Radio Log, 0859, July 3, 1937.</ref> (97)

			:: At 9:35, O’Hare called Cipriani on Howland and told him to “get the direction finder going at all cost.” But it was no good. Half an hour earlier, Cipriani had logged: “All batteries on the island are discharged. Commenced to charge them.” He did not hear O’Hare’s directive and could not have done anything about it if he did.<ref>''Itasca'', RLP1, 0935, July 2, 1937; Howland Radio Log, 1000, July 3, 1937.</ref> (101)

			:: For the next thirty minutes everything was quiet, but then, exactly on the half hour, government radio operators in Hawaii heard dashes and a weak voice signal, this time on Earhart’s other frequency, 6210 kilocycles. It is not clear whether Coast Guard operators at the Hawaiian Station or army operators at Fort Shafter—or both—heard these signals. Dashes and voice heard together suggest that, once again, the transmissions were being sent using a microphone rather than a sending key. Itasca did not hear the signals; the ship’s radio operators were not listening on that frequency. Howland Island did not hear anything either; Cipriani was still recharging his batteries. There is, however, a report that someone else heard a voice at that moment. (118)

			== References ==
			<reference />

	== Bearings taken on transmissions after July 2 ==		== Bearings taken on transmissions after July 2 ==

Rickerjones: /* References */ Add link to Air Navigation

2011-03-07T17:11:14Z

References: Add link to Air Navigation

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	[[Category:Navigation]]		[[Category:Navigation]]
	[[Category:Maps]]		[[Category:Maps]]
			==Related==
			* [[Air Navigation: State of the Art in 1937]]

Rickerjones: Add catagory: Maps

2010-06-10T16:13:53Z

Add catagory: Maps

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	[[Category:Radio considerations]]		[[Category:Radio considerations]]
	[[Category:Navigation]]		[[Category:Navigation]]
			[[Category:Maps]]

Moleski at 16:28, 19 October 2009

2009-10-19T16:28:02Z

← Older revision		Revision as of 16:28, 19 October 2009
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	"Direction finding (DF) refers to the establishment of the direction from which a received signal was transmitted. This can refer to radio or other forms of wireless communication. By combining the direction information from two or more suitably spaced receivers, the source of a transmission may be located in space via triangulation. This is called a cross-cut or fix."[http://en.wikipedia.org/wiki/Direction_finding]		[[File:Shoe9.jpg\|thumb]]"Direction finding (DF) refers to the establishment of the direction from which a received signal was transmitted. This can refer to radio or other forms of wireless communication. By combining the direction information from two or more suitably spaced receivers, the source of a transmission may be located in space via triangulation. This is called a cross-cut or fix."[http://en.wikipedia.org/wiki/Direction_finding]

	== Finding a minimum ==		== Finding a minimum ==

Moleski at 18:17, 13 October 2009

2009-10-13T18:17:34Z

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	"High-frequency direction finding was only developed in the mid 1930s, and the first HF/DF were deployed circa 1936. Apparently HF/DF sets were quite scarce in 1937, and probably largely controlled by OP-20-G, which makes the dispatch of an HF/DF set to Howland retrospectively quite astonishing. Guam asked for an HF/DF set in late May 1937, and was turned down. They were able to "borrow" a set which they reported having had great difficulty getting to work as of September 1937-one wonders if the Howland HF/DF set ended up being to sent to Guam. The Philippines had HF/DF capability in late 1936. [no info found on Hawaii] By 1940 the network was much more extensive, but in 1937, it was pretty rudimentary, and it isn't clear the extent to which the Navy had a real operational capability."<ref>Arthur Rypinski to EPAC, 16 May 2009.</ref>		"High-frequency direction finding was only developed in the mid 1930s, and the first HF/DF were deployed circa 1936. Apparently HF/DF sets were quite scarce in 1937, and probably largely controlled by OP-20-G, which makes the dispatch of an HF/DF set to Howland retrospectively quite astonishing. Guam asked for an HF/DF set in late May 1937, and was turned down. They were able to "borrow" a set which they reported having had great difficulty getting to work as of September 1937-one wonders if the Howland HF/DF set ended up being to sent to Guam. The Philippines had HF/DF capability in late 1936. [no info found on Hawaii] By 1940 the network was much more extensive, but in 1937, it was pretty rudimentary, and it isn't clear the extent to which the Navy had a real operational capability."<ref>Arthur Rypinski to EPAC, 16 May 2009.</ref>

	"The modern broadband [[loop antenna]] depends on a carefully engineered amplifier to keep the sensitivity constant over a wide range of frequencies" ([[Hue Miller]], 30 June 2000 [http://www.tighar.org/forum/Highlights81_100/highlights94.html Forum.)]		"The modern broadband [[loop antenna]] depends on a carefully engineered amplifier to keep the sensitivity constant over a wide range of frequencies" ([[Hue Miller]], 30 June 2000 [http://www.tighar.org/Projects/Earhart/forum/Highlights81_100/highlights94.html Forum.)]

	Pan Am's HFDF equipment is described in detail in [[Bob Brandenburg]]'s article, [http://tighar.org/Projects/Earhart/Research/ResearchPapers/Brandenburg/RDFResearch/RDFAnalysis/RDFAnalysis.htm Radio Direction Finder Analysis.]		Pan Am's HFDF equipment is described in detail in [[Bob Brandenburg]]'s article, [http://tighar.org/Projects/Earhart/Research/ResearchPapers/Brandenburg/RDFResearch/RDFAnalysis/RDFAnalysis.htm Radio Direction Finder Analysis.]

Moleski: /* Finding a minimum */

2009-10-13T00:24:23Z

Finding a minimum

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	[[Image:Minimum found.png\|thumb\|200px\|right\|Red bar--directional antenna.]]		[[Image:Minimum found.png\|thumb\|200px\|right\|Red bar--directional antenna.]]
	[[Image:Maximum found.png\|thumb\|200px\|right\|Red bar--directional antenna.]]		[[Image:Maximum found.png\|thumb\|200px\|right\|Red bar--directional antenna.]]
	If one has a directional receiver antenna, it is possible to find the direction from which a transmission is coming by rotating the antenna (as with Eahart's [[loop antenna]] or, if the antenna is fixed, ~~fly~~ the aircraft in a circle. In either case, the goal is to find the point in the rotation or the circle where the signal is weakest. At that point, the transmitter ''must'' be at a 90 degree angle to the axis in which the antenna is most sensitive. If no other information is available other than that derived by the ~~rotation~~ of the antenna, one would not know whether the signal was to the 90 degrees to the left or 90 degrees to the right of the antenna's bearing at the minimum.		If one has a directional receiver antenna, it is possible to find the direction from which a transmission is coming by rotating the antenna (as with Eahart's [[loop antenna]] or, if the antenna is fixed, by flying the aircraft in a circle. In either case, the goal is to find the point in the rotation or the circle where the signal is weakest. At that point, the transmitter ''must'' be at a 90 degree angle to the axis in which the antenna is most sensitive. If no other information is available other than that derived by the movement of the antenna, one would not know whether the signal was to the 90 degrees to the left or 90 degrees to the right of the antenna's bearing at the minimum.

	There are many ways to resolve the ambiguity in the information provided by the directional antenna. One way is to move to a new position and take a new reading. The second reading should provide a triangulation pointing to the radio source.		There are many ways to resolve the ambiguity in the information provided by the directional antenna. One way is to move to a new position and take a new reading. The second reading should provide a triangulation pointing to the radio source.

Moleski at 00:22, 13 October 2009

2009-10-13T00:22:56Z

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	== Direction finding on the final flight ==		== Direction finding on the final flight ==
	=== Previous procedure (Oakland to Honolulu) ===		=== Previous procedure (Oakland to Honolulu) ===
	On the flight from Lae to Howland, [[Earhart]] and [[Noonan]] planned to use the simplest form of radio direction finding: find where the transmission was coming from and fly toward it. On the flight from Oakland to Honolulu, Manning and Noonan took seven radio bearings.<ref>[http://www.tighar.org/Projects/Earhart/ResearchPapers/Worldflight/prepdepart.html Preparations for departure.]</ref>		On the flight from Lae to Howland, [[Earhart]] and [[Noonan]] planned to use the simplest form of radio direction finding: find where the transmission was coming from and fly toward it. On the flight from Oakland to Honolulu, Manning and Noonan took seven radio bearings.<ref>[http://www.tighar.org/Projects/Earhart/Research/ResearchPapers/Worldflight/prepdepart.html Preparations for departure.]</ref>
	=== Lack of CW skills made DF difficult ===		=== Lack of CW skills made DF difficult ===
	From the [http://www.tighar.org/Projects/Earhart/Documents/Chater_Report.html Chater Report:]		From the [http://www.tighar.org/Projects/Earhart/Documents/Chater_Report.html Chater Report:]

Moleski: /* High frequency direction finding (HFDF) */

2009-10-12T19:43:18Z

High frequency direction finding (HFDF)

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	"The modern broadband [[loop antenna]] depends on a carefully engineered amplifier to keep the sensitivity constant over a wide range of frequencies" ([[Hue Miller]], 30 June 2000 [http://www.tighar.org/forum/Highlights81_100/highlights94.html Forum.)]		"The modern broadband [[loop antenna]] depends on a carefully engineered amplifier to keep the sensitivity constant over a wide range of frequencies" ([[Hue Miller]], 30 June 2000 [http://www.tighar.org/forum/Highlights81_100/highlights94.html Forum.)]

	Pan Am's HFDF equipment is described in detail in [[Bob Brandenburg]]'s article, [http://~~www.~~tighar.org/Projects/Earhart/Research/~~Bulletins~~/~~50_RDFAnalysis~~/~~50_RDFAnalysis~~.htm Radio Direction Finder Analysis.]		Pan Am's HFDF equipment is described in detail in [[Bob Brandenburg]]'s article, [http://tighar.org/Projects/Earhart/Research/ResearchPapers/Brandenburg/RDFResearch/RDFAnalysis/RDFAnalysis.htm Radio Direction Finder Analysis.]

	* [http://en.wikipedia.org/wiki/HFDF Wikipedia.]		* [http://en.wikipedia.org/wiki/HFDF Wikipedia.]

Moleski: /* Bearings taken on transmissions after July 2 */

2009-10-12T19:42:56Z

Bearings taken on transmissions after July 2

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	== Bearings taken on transmissions after July 2 ==		== Bearings taken on transmissions after July 2 ==
	[[Image:Allbearings.jpg \|thumb\|250px\|HFDF bearings taken on post-loss transmissions converge on the area around Gardner Island.]]		[[Image:Allbearings.jpg \|thumb\|250px\|HFDF bearings taken on post-loss transmissions converge on the area around Gardner Island.]]
	* [http://~~www.~~tighar.org/Projects/Earhart/Research/~~Bulletins~~/~~50_RDFAnalysis~~/~~50_RDFAnalysis~~.htm Brandenburg: Radio Direction Finder Analysis.]		* [http://tighar.org/Projects/Earhart/Research/ResearchPapers/Brandenburg/RDFResearch/RDFAnalysis/RDFAnalysis.htm Brandenburg: Radio Direction Finder Analysis.]

	== References ==		== References ==