Lutjens' Intentions

Discussions about the history of the ship, technical details, etc.

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tommy303
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Re: Lutjens' Intentions

Post by tommy303 » Sun Aug 25, 2013 7:50 pm

The Germans claimed, although it has not been verified to my knowlege, B-Dienst's scanners could pick up stray emissions from seagoing radios at up to 100nm for older sets of which there were a great many at sea; newer sets were only detectable at somewhat lesser ranges. As stated previously, the Germans probably operated on the basis of what one can do, so can another. The only way to minimize the danger of an enemy homing in on stray emissions was to either shut down the radio altogether or, more probably as Dan suggests, disconnect the set from the arials. At any rate, they appear to have devoted time and money to develope detectors or particularly sensitive radio receivers which could accomplish this. It make sense from the German point of view, as in a commerce war, any advantage you can gain, no matter how small, might have far reaching consequences. That the British concentrated more on direct direction finding of actual transmissions made sense from their point of view as well, as they were at least early on, on the defensive and in any event, the primary danger was from U-boats and their radios were relatively low power and left little signature to detect unless actively transmitting.

You may be correct concerning the 'leak' being Metox rather than radio receivers.

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Re: Lutjens' Intentions

Post by Dave Saxton » Mon Aug 26, 2013 1:49 am

wadinga wrote:Hi Tommy and Dan and All,

It seems to me the example you are thinking of is the ruse employed by a captured RAF crewman who managed to persuade his captors that the Metox radar detector/receiver employed by u-boats emitted a signal that could be homed in on by patrolling aircraft. U-boats were consequently instructed to keep their very useful Metox switched off by this entirely spurious claim.

Surely these very low intensity emissions must have been almost impossible to detect, since all interception and D/Fing accounts concentrate on active transmission rather "leakage" of signal from transmitters on stand by or indeed receivers in passive mode.
Quite true Sean about the crewman (who remains unknown) giving U-boat Command the idea that the ASW aircraft were homing in the local osculator emmisions of the Metox receivers during mid 1943. The Allies did not use this to locate U-boats even if technical possible though. U-boat Command was at its wits end trying figure out how the enemy was locating the U-boats and was more than willing to believe it. B-diesnt was reading the RN signal traffic at the time reporting on each U-boat destroyed and it usually contained the phrase: "Radio Located". This could mean radar of course, but it could also allude to Huff Duff or to Ultra which the Germans did not really suspect. It could also allude to radio emissions from LOs which the did suspect. The LO affair only lasted a few months but resulted in the sacking of Adm Maertens. Doenitz finnally decided it was radar and did not of course realize it was also other factors such as Ultra.

The biggest problem for U-boat command was they were operating in the ingorance of Rotterdam and Meddo (the knowlege of enemy centimetric radar). Because of the severe secrecy protocols nobody within U-boat Command was properly informed about Rotterdam. The AGR of course knew the real cause and had given top priority to providing a centimetric radar detector. Others within KM knew all about Rotterdam but dare not say anything.

Unbelievable it is, but true, that Telefunken (who knew all about Rotterdam) supported the LO theory by informing U-Boat Command that the Metox LO emissions could be detected up to 80km away from an airborne platform when they were asked. Use of the Metox was banned and the Wanze was authorized to be used in stead. The Wanze LO emissions were much less than Metox's but the losses continued, because the Wanze could not detect the new centimetric ASV either. The Wanze was then banned to be replaced by Borkum and then later by Wanze II (with no super het LO) By early 44 it was finnally known at U-boat Command that the real cause was centimetric ASV and the Tunis and Naxoz ZM were becoming available.

Your also quite right that the Metox remained useful, albeit in diminished capacity, into late 1943. Most of the Allied patrol bmbers still used 1.4 meter wave length ASV into 1944.

There was another interrogation, this time of a captured American radar tech, that had revealed the truth. The tech gave German Naval Intel a complete tutororal of both 10cm and 3cm Allied radar. But even then it appears that U-boat Command remained in the dark.

By early 1944 U-boat skippers were so wary of any radio use that U-boat Command had to issue orders ordering them to use Hohentwiel radar at all times when on the surface- if equipped. (Hohentwiel could locate a patrol bomber well before the patrol bomber could in turn locate a surfaced U-boat using ASV.) Otherwise they would not operate any radar devices no matter how benign.
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Re: Lutjens' Intentions

Post by wadinga » Mon Nov 04, 2013 6:34 pm

All,

Interesting article at http://www.cdvandt.org-DEHS2008-def.pdf confirms the 1-100 sequential message number plus lots of interesting electronic warfare snippets.

All the best

wadinga
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Re: Lutjens' Intentions

Post by sineatimorar » Thu Nov 21, 2013 10:58 pm

In the staring posts and other comments made by the Vic I note two points, one is a assumption and one of omission. Others have Tryed to make this point in this.

The assumption that the bow was patched with steel plugs sheets. I think he bases his premises on the conclusion that as the plugs had been made, they must have been used. This ignores the additional information from the same sources that as Lutjen thought they had shadowing enemy stopping the ship was not possible.

The omission of facts by Vic is over the evidence available on the hit to torepodo protection system of a 14 inch shell; The immediate damage caused by this hit was a flooded electric room, damage not only to the oil bunkers, but more importantly, the feed water bunkers and resulting sea water contamination and a barely contained flooding of one boiler room.

The only confirmed patch placed over bow holes was a sail / canvas style patch. Sea action at higher speeds would disturb this patch thus limiting top speed.

The 14 inch hit to the TPS was clearly of more importance in the decision to dock at Brest. For the bow hit was repairable at sea, this hit clearly required a dry dock to fix.

While the extract amount of oil made unusable by the damage maybe upto debate. The loss of uncontaminated feed water storage for the boilers is the crux of the decision. Less storage capacity equals reduced steam volume which is the limitation behind the reduced top speed to approx 24 to 26 knots if flooding forward is contained.

Completely ignored is the first aerial torepdo hits. While no extra damage was caused by theses hits, the shock forces opened the damaged and leaking seams into the boiler room, thus completely flooding compartment. There goes any chance of maintaining 26 knts let alone the 29 knt figure initially posted. I think I remember the report that two boilers were off line anyway due to the feed water contamination?.

There are a number of other points of fact ignored in this argument on standard naval practices when faced with boiler damage, the effects of counter flooding and the effects that has on fuel consumption, the increasing sea conditions with similar effects on fuel consumption as well. You simply can not go on fuel consumption figures obtained in ideal conditions. The last point probably goes a long way to the reason German warships used markedly extra amounts in actual combat patrols.

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