113:. Mitchell installed an identical loop outside of the channel for vessels, the two loops were connected so that the random fluctuations cancelled each other out. A rheostat was used to give the two loops identical resistances, so that no current flowed until a vessel approached. Unfortunately, his report to the BIR was misunderstood and his findings rejected as of no value. Consequently, there was a hiatus in the installation of loops until their utility was demonstrated beyond question. Under Bragg's leadership, a number were installed. Later in World War I the tiny induced voltages were amplified by
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180:(Portland Naval Base). In WWII indicator loops were used by the Allies for harbour defence in the UK and its dominions and protectorates, as well as by the US Navy. For example, the Hoxa channel into Scapa Flow was provided with two guard loops followed by eight mine loops in echelon.
165:, induced by the submarine as it passed over the cable. Activation of the loop detonated mines in the field, sinking the submarine. UB-116 was the last U-boat destroyed by enemy action before the Armistice, ironically when it had no prey. The wreck of
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The "Liverpool Cable" used for the loops consisted of four-core, single strand 1.23 mm copper wire, sheathed in two-layer rubber insulation of 3.7 mm diameter, that was wrapped in
194:, but that signal was ignored, owing to civilian traffic in the area. The submarine was soon sighted visually, after it became entangled in a submarine net and its bow broke the surface.
161:. There were no allied vessels in the harbour so the indicator loops on the minefields were activated. Two hours later, at 23:32, current was detected in an indicator loop laid in a
58:(BIR), composed of a three-man central committee supported by an eminent consulting panel. The remits of Section II of the panel, the members of which included physicists
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136:, and armoured with 26 strand 2.0 mm steel wire, giving a final diameter of 18.8 mm. The cores were wired together when the cable was used for a loop.
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was raised in 1919 but foundered while being towed. Its broken-up scraps fell back onto the seabed, where now they are popular with scuba divers.
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109:. Voltages were also induced in the cable by random fluctuations in the Earth's magnetic field and electrical noise from the
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In the early years of World War I submarines were fearful, one-sided weapons because they were invisible. In July 1915
153:, captained by Lieutenant J J Emsmann, who, along with his crew had volunteered for a suicide mission, was detected by
101:, who was helped by the Royal Navy at HMS Tarlair. He had shown that the passage of a submarine past a cable formed an
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identification tape. The cores were separated by five strands of 36-thread cotton serving, wrapped in two layers of
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After the First World War, indicator loop devices were further developed by the
Admiralty's research divisions at
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identification tape, all encased in a 12.8 mm diameter lead sheath that was wrapped in 18 strands of tarred
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Mitchell, A C. On the vertical force changes during the "sudden commencement" of a magnetic storm.
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was a submerged cable laid on the sea bed and used to detect the passage of enemy submarines.
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Independently from the BIR, in August 1915, a submerged cable was laid on the seabed of the
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amplifiers. Even with that assistance, a long loop installed to monitor traffic in the
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which induced a voltage of approximately a millivolt, detectable by a sensitive
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https://www.academia.edu/6720520/Bragg_and_Mitchell_s_Antisubmarine_Loop
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54:. Balfour appreciated the importance of science, so he established a
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Submerged - Shipwrecks And Scuba Diving Around Devon And The World
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at 21:21 on 28 October 1918 while entering the harbour via
278:. Aberdour: Aberdour Cultural Association. p. 58.
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Walding, R 'Bragg and
Mitchell's Antisubmarine Loop',
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An indicator loop gave the first warning of the 1942
70:. Bragg soon moved to the hydrophone research centre
97:. The idea originated with the Scottish physicist
450:"What are Indicator Loops and how do they work?"
78:on the Firth of Forth (which later relocated to
139:A notable operational use of a loop was at the
300:Proceedings of the Royal Society of Edinburgh
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226:Andrade, E. N. de C.; . Lonsdale, K (1943).
350:. Aberdour: Aberdour Cultural Association.
315:, 46 (2009), 140-145. Available online at
505:Weapons and ammunition introduced in 1915
375:. Periscope Publishing Ltd. p. 92.
373:Torpedoed! The R.M.S. Leinster Disaster
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431:from the original on 25 February 2009
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215:. Stroud: Fonthill. pp. 93–128.
302:Vol. 45, no. 26 (1925) pp. 297-301.
213:Great Scientists wage the Great War
421:"Indicator Loops around the World"
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477:. Edinburg: Birlinn. p. 243.
264:Van der Kloot 2014, pp. 129-161.
228:"William Henry Bragg, 1862-1942"
510:1915 establishments in Scotland
211:Van der Kloot, William (2014).
56:Board of Invention and Research
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163:remotely controlled minefield
89:Underwater loop configuration
32:anti-submarine indicator loop
27:Submarine detection equipment
475:This great harbor Scapa Flow
99:Alexander Crichton Mitchell
52:First Lord of the Admiralty
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232:Biogr. Mem. Fellows R. Soc
327:Walding 2009, pp. 140-145
185:attack on Sydney Harbour
473:Hewison, W. S. (2002).
371:Lecane, Philip (2005).
346:Maxwell, Diana (2014).
274:Maxwell, Diana (2014).
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495:Anti-submarine warfare
244:10.1098/rsbm.1943.0003
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336:Walding 2009, pp. 144
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121:proved impractical.
500:Scottish inventions
64:William Henry Bragg
454:Indicatorloops.com
425:Indicatorloops.com
313:Australian Physics
111:Glasgow tram lines
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382:978-1-904381-29-7
357:978-0-9929470-1-9
285:978-0-9929470-1-9
60:Ernest Rutherford
48:Winston Churchill
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155:hydrophones
141:Grand Fleet
115:vacuum tube
82:in Essex).
72:HMS Tarlair
68:hydrophones
489:Categories
459:2008-06-10
435:2009-03-01
406:2008-06-10
198:References
178:HMS Osprey
174:HMS Vernon
159:Hoxa Sound
145:Scapa Flow
348:Listen Up
276:Listen Up
252:202574479
46:replaced
429:Archived
397:"UB.116"
76:Aberdour
80:Harwich
38:History
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167:UB-116
150:UB-116
248:S2CID
130:linen
377:ISBN
352:ISBN
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192:M-14
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