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#1
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Intellgence agencies when they did HFDF used huge antenna arrays
called CDAAs (Circular Disposed Antenna Arrays). They were also known as Wollenwebbers (presumably after an inventor). These arrays were often very large, and sometimes were affectionally known as "elephant cages." The diameter of these arrays could be as small as 50-60 feet for a tactical unit to several hundred feet for large fixed sites in a secure area. Each circle had many vertical elements. They measured time difference of arrival by measuring the wavefront timing on each antenna in the array as the wave passed through the array. A computer then collated this information to calculate a bearing. The readouts varied depending upon the era. Some were digital, some were on an oscillicsope. I'm not quite sure how the really early ones worked (before my time). The results of several stations were then combined to get a "fix." Contrary to popular belief, their accuracy had significant error factors so despite many requests from military commanders who wanted to drop ordinance on a target, you really couldn't do that based solely on HFDF. HFDF was really originally intended for open ocean surveillance against things like German subs in both WW I and WW II. You could get a rough idea where a signal was coming from and then you would have to sent a destroyer or aircraft to actually locate the sub. There are other types of HFDF antennas as well, but none can give pin point accuracy unless you are mobile and close in as in transmitter hunts. As long at there was energy, you could get a bearing be it a sustained carrier or a single dit. You would have to rely on other externals (callsigns, radio finger printing etc) to figure out who was sending a given signal. W3JT On 18 Feb 2005 06:29:34 GMT, (Martin Potter) wrote: "RB" ) writes: Wonder if loop antennas were what they really used, and how good they were? The spies generally used cw. How do you get a fix on the short dots and dashes? With AGC turned off, just listen for the null in the signal as the loop is rotated. |
#2
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Wullenweber: German for wool weaver. Germans had several in WW2, none existed elsewhere. Sites were stripped and
burned and the big iron goniometers buried during the closing days of the war. Took quite a bit of effort by ONR and OSS to retrieve enough material to reconstruct the concept. And a lot of work at U of Ill. and ITT/FTR to make one work. Beamformers, not TOA. That came a lot later. The initial question was set in the WW2 time period, I believe. Crazy George the ATTGlobal.net extension is a SPAM trap. Use att dot biz instead. |
#3
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In message , Crazy George
writes Wullenweber: German for wool weaver. Germans had several in WW2, none existed elsewhere. Sites were stripped and burned and the big iron goniometers buried during the closing days of the war. Took quite a bit of effort by ONR and OSS to retrieve enough material to reconstruct the concept. And a lot of work at U of Ill. and ITT/FTR to make one work. Beamformers, not TOA. That came a lot later. The initial question was set in the WW2 time period, I believe. Crazy George the ATTGlobal.net extension is a SPAM trap. Use att dot biz instead. -- |
#4
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In message , Crazy George
writes Wullenweber: German for wool weaver. Germans had several in WW2, none existed elsewhere. Sites were stripped and burned and the big iron goniometers buried during the closing days of the war. Took quite a bit of effort by ONR and OSS to retrieve enough material to reconstruct the concept. And a lot of work at U of Ill. and ITT/FTR to make one work. Beamformers, not TOA. That came a lot later. The initial question was set in the WW2 time period, I believe. Crazy George the ATTGlobal.net extension is a SPAM trap. Use att dot biz instead. Ah, Crazy, you got in first! Ian. -- |
#5
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On Fri, 18 Feb 2005 18:21:07 -0600, "Crazy George"
wrote: The initial question was set in the WW2 time period, I believe. I started the topic. It was set in WW2 because I see so much about RDF at that time. i realize it has to have improved by now but the heart of the question is 'since it was possible to be accurate then, why can't hams accurately do it today?' I am thoroughly enjoying this thread. Thank you to ALL that have replied. Buck N4PGW -- 73 for now Buck N4PGW |
#6
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On Sun, 20 Feb 2005 10:18:25 -0500, Buck wrote:
On Fri, 18 Feb 2005 18:21:07 -0600, "Crazy George" wrote: The initial question was set in the WW2 time period, I believe. I started the topic. It was set in WW2 because I see so much about RDF at that time. i realize it has to have improved by now but the heart of the question is 'since it was possible to be accurate then, why can't hams accurately do it today?' I am thoroughly enjoying this thread. There is really two types of DF. Long haul and close in. The close in type which generally uses some sort of null loop from a mobile platform (such as a car or on foot) is what is generally used in "fox hunting" types of transmitter hunts by hams and other hobbists. By extension, the military also use some of this close in technique from tactical aircraft although the technology is different. Long haul, such as was employed in WW II for sub hunting in the Atlantic was done from fixed shore facilities for the most part which exchanged their lines of bearings via a dedicated secure network. Close in DF is accurate only in the sense that the hunter can usually move in close to the target to the point that they can actually see the antenna. Long Haul DF cannot pinpoint a target. Long haul DF stations have known error tolerances and so-call "fixes" are stated with circular or elliptical errors of probabilities. So one might DF a transmitter operating in the Atlantic from shore stations around the perimeter of the Atlantic. The fix will be stated with some degree of tolerance such as there is a 90% chance the target is within an ellipse 100 miles long and 50 miles wide and a 10% chance it is within a 15 by 5 miles area within that larger circle. This is of course still many hundreds or even thousands of sqare miles to hunt for a target. I do not know what technology the Allies used during WW II for their HFDF or what sort of accuracy they achieved. In a WW II scenario, it would be an important intelligence fact if one could discern if a target was near Bermuda or if it was near the Azores. Then a destroyer or subchaser or small carrier with aircraft would have to be dispatched to try to find it if it were on the surface. Allied sub hunting was successful because German doctrine called for frequent situation reports from submarines to shore commands in France and Germany. US submarine operations in the Pacific were more successful in a defensive perspective since they usually operated with a doctrine of radio silence and only rarely sent messages to shore station or to each other. It must be remembered that WW II era subs generally operated on the surface and submerged mostly for attack or self protection. The German sub commanders were in essence victims of Doenitz' tendency to micromanage and they sustained casualty rates of 70% or greater. US sub forces by comparison had casualty rates of 15% which was still among the highest among US forces. Germany had roughly four or five times as many submarines as did the US. [Folks unfamiliar with WW II history must also note that the US had almost no sub forces in the Atlantic since Germany had only a very small surface Navy and almost no coastal or open ocean shipping. A sub of that era was a poor platform to wage war against another submarine. Japan, being an island, was dependant upon ocean shipping for supplies and so was more of a natural target for anti-shipping submarine operations. US subs of course also attacked combatants, but many of those combatants were escorts for shipping convoys. Virtually all US submarines operated in the Pacific Theater. The Brits did have some submarine operations in the Atlantic.] Jon W3JT Thank you to ALL that have replied. Buck N4PGW |
#7
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Jon, W3JT wrote:
"Folks unfamiliar with WW II history must also note that the US had almost no sub forces in the Atlantic since Germany had only a very small surface Navy amd no coastal or open shipping." The emphasis should be on the "almost"! Germamy began the war with 3 formidable "pocket battleships" as I recall. There were American submarines in the Atlantic. Headquarters are at New London, CT. My brother was a WW-2 U.S. Navy submarine officer. His boat was stationed in the Atlantic operating from the U.S. Virgin Islands. He managed a leave home by snagging rides on Catalina flying boats conducting anti-submarine patrols in the Atlantic. He observed real anti-submarine actions while a passenger aboard the Catalinas. My brother was assigned to a new ship from its keel laying. He took it through the Panama Canal to the Pacific where after several missions it became a craft on permanent patrol as the result of enemy action with no known surviors. His family misses him. Best regards, Richard Harrison, KB5WZI |
#8
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"Richard Harrison" wrote in message ... Jon, W3JT wrote: "Folks unfamiliar with WW II history must also note that the US had almost no sub forces in the Atlantic since Germany had only a very small surface Navy amd no coastal or open shipping." The emphasis should be on the "almost"! Germamy began the war with 3 formidable "pocket battleships" as I recall. There were American submarines in the Atlantic. Headquarters are at New London, CT. My brother was a WW-2 U.S. Navy submarine officer. His boat was stationed in the Atlantic operating from the U.S. Virgin Islands. He managed a leave home by snagging rides on Catalina flying boats conducting anti-submarine patrols in the Atlantic. He observed real anti-submarine actions while a passenger aboard the Catalinas. My brother was assigned to a new ship from its keel laying. He took it through the Panama Canal to the Pacific where after several missions it became a craft on permanent patrol as the result of enemy action with no known surviors. His family misses him. Best regards, Richard Harrison, KB5WZI A great book on German submarine warfare off the US coast -- is "Operation Drumbeat" by Michael Gannon I too lost fanily members at Normandy and Anzio We do remember -- Caveat Lector (Reader Beware) Help The New Hams Someone Helped You Or did You Forget That ? |
#9
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Richard Harrison wrote:
Jon, W3JT wrote: "Folks unfamiliar with WW II history must also note that the US had almost no sub forces in the Atlantic since Germany had only a very small surface Navy amd no coastal or open shipping." The emphasis should be on the "almost"! Germamy began the war with 3 formidable "pocket battleships" as I recall. There were American submarines in the Atlantic. Headquarters are at New London, CT. My brother was a WW-2 U.S. Navy submarine officer. His boat was stationed in the Atlantic operating from the U.S. Virgin Islands. He managed a leave home by snagging rides on Catalina flying boats conducting anti-submarine patrols in the Atlantic. He observed real anti-submarine actions while a passenger aboard the Catalinas. My brother was assigned to a new ship from its keel laying. He took it through the Panama Canal to the Pacific where after several missions it became a craft on permanent patrol as the result of enemy action with no known surviors. His family misses him. Best regards, Richard Harrison, KB5WZI Richard; All of us are grateful for your brother's dedication to his country. Dave WD9BDZ |
#10
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In message , J. Teske
writes Intellgence agencies when they did HFDF used huge antenna arrays called CDAAs (Circular Disposed Antenna Arrays). They were also known as Wollenwebbers (presumably after an inventor). Is 'Wollenwebber' really 'Wollenweber', which I reckon could be translated as 'wool weaver'? Possibly a graphic description of the antennas. Ian. -- |
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