What if Hood hadn't blown up?

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Re: What if Hood hadn't blown up?

Post by RF » Sat Mar 28, 2009 10:47 am

Taking in what you say and transfering these considerations to the tactical and strategic level, two factors come to my mind.

Firstly the pessimistic disposition of Lutjens, as reflected in his reports and actions. The radar has to clearly be accounted for in future German operations, but the options they could use were not properly considered. A commander more aggressive and a navy without an inferiority complex might have chosen more robust responses.

Secondly the fact remains that Bismarck came very close to escaping to France. Radar in itself can track ships, it is not a weapon to sink them.
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Re: What if Hood hadn't blown up?

Post by Dave Saxton » Sat Mar 28, 2009 1:23 pm

Hence the long term response of the Kriegsmarine was an emphasis (if not an obsession) with improving the effective range of their radar equipment. Indeed later documents reveal that they placed high priority upon improved range performance especially with regard to radar directed long range gunnery aspects.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

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Re: What if Hood hadn't blown up?

Post by Vic Dale » Sun Mar 29, 2009 2:55 pm

To all.

I think there is a very big difference between weapons-fit including electronic warfare equipment carried in the ship and the potential for experiment using jury rigged and highly experimental gear, constructed in the ship's radio workshop. If radar pulses can be detected and received it is a relatively simple matter to add a known and lower radio frequency to the reception and count the beat. This will establish the frequency of the incoming signal, even though perhaps not very precisely. Such experimentation is not beyond the capabilities of normal ship-born technicians who are constantly playing about and experimenting and given that the Fleet Technicians were aboard, the order to establish the frequency of the new radar is not unreasonable.

Most certainly the direction of incoming pulses can be detected by simple power alone and tuning for the null position. Screening one end of the detecting Di-Pole will indicate the quadrant from which the pluses are coming. I built a simple detector of this type myself in the 1960s before I even began work. I used a transistor radio and interference from the radar of passing warships.

It is not possible to determine range from incoming pulses, but the working range of the set is not hard to establish. All you need to do is take note of where the shadowing ship is when the weather suddenly clears. That gives the radar's effective range. Turning and firing on the shadowers as Lutjens did, ensures that they keep well away and as far out as they can whilst maintaining contact. That is roughly the set's effective range.

Lutjens' estimate was 35,000 yards or 17.5 miles about five miles too much. This is a reasonable assessment, because he could not know that the British Captain was gambling on regaining contact after having briefly lost it. This tactic turned out to be Captain Ellis' undoing. He was operating beyond the set's capabilities and that cost him contact with the German. We can't be sure that Lutjens did not realise later what was going on, enabling him to judge that the British ship was out beyond her radar range and evade her, even though he did not transmit the information to Group West.

B-Dienst aboard Bismarck was intercepting and breaking British coded messages very quickly and possibly Lutjens received intelligence regarding Britain's ability to crack enigma or the U-Boat code. We cannot take any signals sent by Lutjens simply at face value.

That Lutjens signalled that the British were maintaining contact at 0700 on the 25th after they had lost contact could be due to one of two things;

A. He may not have made off to the southeast immediately after losing Suffolk, as is thought, due to the surveillance cover from the carrier which he knew was to his north and he may well have been able to see the shadowing squadron's smoke trails on the horizon. Radio traffic from the attacking aircraft could be easily monitored.

B. He may have sent that signal on learning that Wake-Walker was concentrating his search to the west, assuming that as it was sent on the brief U-Boat code (Kurtzignal) which was probably becoming suspect, that Wake Walker would read it and assume that he was doing the right thing. There are a number of signals which do not make sense in themselves, but taken as signals intended for possible consumption by the enemy, they make a lot of sense.

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Re: What if Hood hadn't blown up?

Post by lwd » Sun Mar 29, 2009 3:32 pm

Vic Dale wrote:.... If radar pulses can be detected and received it is a relatively simple matter to add a known and lower radio frequency to the reception and count the beat. This will establish the frequency of the incoming signal, even though perhaps not very precisely...
If you get close enough to hear a beat you are already close enough. Detecting beats from intermittent signals is also pretty difficult.

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Re: What if Hood hadn't blown up?

Post by Dave Saxton » Sun Mar 29, 2009 5:45 pm

Vic,

Are you talking about the pulse repitition frequency, or super het beats created by mixing the frequency of a local osscilator with the incoming radar frequency? The problem I can see with that technique is that the LO frequency must be fairly close to the operating frequency. Just as a strong and rapid beat is produced by two guitar strings close but not quite to being in tune with each other, the LO frequency would need to be a specific frequency close to 600Mhz to mix with the operating frequency properly. The neccessary componants in the form of Philips brand vacuum tubes would have been available on German ships, but I think we are speculating way too much to assume that they improvised detection equipment for 51.5cm detection in the Bismarck's work shops during the heat of the moment.

Approximate directional detection via max signal would have required some form of trainable antenna array, along the lines of the phased array Timor (that worked with Samos detector) installed on the Tirpitz within just a short few months of the Bismarck operation. Or dipoles positioned so that they gave a rough estimate of direction such as the Sumatra dipoles (that also worked with the Samos). None of these type of antenna apparatie can be identified in photos of the Bismarck. Nevertheless professional detection receivers were already available and in use by the KM from at least a year earlier in the form the NVK snooping recievers. It is quite possible that Bismarck was equipped with one or more NVK radar detection recievers, but it is not known for certain. A very small omni-directional antenna code named Bali may have been available as well.

Getting back to Luetjens' tactical options; Luetjens probably duduced that the British were loosing or close to loosing contact during the outboard leg of their zig zag. He could monitor the course and behavior of the Prince of Wales and the two large cruisers and formulate a plan. His radar had at least the same range to large ships as did the Suffolk's 284 to his ship in actuallity. Of course Luetjens mistakenly assumed that the British radar had far greater effective range than it actually did. The British made an error by putting all of their ships close to POW far distant off the Bismarck's port quarter. However, it remains that Luetjens didn't seem to realize that his plan to break contact had actually worked and still assumed that WW maintained radar contact as late as 0700. Breaking radio silence if he knew they had lost contact for whatever reason just doesn't make sense to me.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

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Re: What if Hood hadn't blown up?

Post by Vic Dale » Sun Mar 29, 2009 6:43 pm

To Dave.

I am thinking about a local oscillator as in the intermediate stage of an ordinary radio receiver which brings the carrier wave down to something which the valves or transistors can handle.

Adding a relatively low frequency to a high one causes a beat every so many matching peaks effectively dividing the higher frequency. Taking the resultant frequency produced by the combination of the high and low signals and then multiplying that by the lower frequency, the higher frequency should be revealed. It should not require specially developed valves to do this.

Or have I missed something? It has been a very long time.

Lutjens does not say anything about the British being in "Radar" contact, just; "One Battleship two Cruisers maintain surveillence." Sent at 0700 and with Wake-Walker now chasing to the west, it could mean anything.

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Re: What if Hood hadn't blown up?

Post by Dave Saxton » Sun Mar 29, 2009 7:39 pm

Hi Vic,

As I understand it the LO needs to be able to operate at a frequency reasonably close the operation frequency. In technical manuals for example, the 9cm Berlin had to use a magnetron that operated at close to 3ghz for the LO. Allied centimetric radar used klystrons at microwave frequencies for the LO. Decimetric radar seems to specify special multi-element tubes for the LOs. Additionally, the recieving pentodes and mixxing tubes do need to be rather specialized for operation on the frequencies of radar, which even for metric radar are considerably higher frequencies than typical communications radio. The valve/tube technology that made radar at the decimetric wave lengths possible only came into being with the invention of the RCA Acorn pentode types in America during the mid 1930's. The Dutch firm of Philips and the British firm of Mullard built improved versions in Europe. Telefunken, GEMA, and Lorenz had their own tube labs and manafacturing facilities to make specialized tubes. The Germans had military grade derivatives of the Philips tubes (with Werhmach part numbers) on hand because they not only used decimetric radar but also UHF talk between ships equipment. I think that the UHF bands were well beyond the capability of the normal communications radio tube circuits and componantry of the time.

Luetjens would have to assume that the British were probably tracking him with radar if he thought they were still maintaining contact ,but they were nowhere to be seen or not being picked up by hydrophones.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

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Re: What if Hood hadn't blown up?

Post by Vic Dale » Mon Mar 30, 2009 9:35 pm

To Dave.

I am in the deep end here and I am not a good swimmer.

My point is that passive interception of a signal and reading the frequency is far easier than constructing a working radar and does not essentially require manufactured kit, or more than a fraction of the components used to make a working radar set. If you can recieve then you must have a receiver of some sort which can work at the required frequency and variable tuning will tell you what that frequency is.

Radio labs check out and use radio frequencies at all levels, so if intelligence gathering was the order of the day, then the Fleet Technicians would carry the necessary test equipment as part of their personal kit, even though that equipment may not figure as part of the ship's complement of technical gear - whether or not Bismarck herself carried a passive detector.

We don't have any more information about what Lutjens knew or did not know than that brief signal and we do not even know precisely what the signal meant. The Kurtzignale was a preworded code consisting of expressions to cover a number of situations, which by their very nature could not give the precise meaning which a specifically worded message which was encrypted using Enigma would give.

As far as the British were concerned, Bismarck had to be within a circle of known diameter, with a radius determined by her farthest-on from the time contact was lost. They knew where she was, but they could not see her.

At the time this signal was sent (0700) Bismarck was safe inside all three ship's blind sectors astern so as radar was suspected - indicating a passive detector of some sort - no pulses would have been getting to the ship. That Lutjens' orignal signal about enemy radar is so definite in stating the range etc, it is almost certain that she was using a passive detector.

Had knowledge of British radar been gained through B-Dienst interceptions, this would have figured in at least some of the communications and an indication of "assumption" would have been given rather than the very definite statements which were made.

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Re: What if Hood hadn't blown up?

Post by Dave Saxton » Tue Mar 31, 2009 4:02 am

It's the ambiguity of it that is troubling and I'm not sure how I should best address this in my work yet. I want to avoid too much speculation on the matter. Had the KTB been saved or had any personal privy to these matters been saved we would know more.

I'm inclined to believe that Bismarck had some detection gear and that it was probably the NVK stuff. What I remain sceptical of is that they specifically identified and monitored the Suffolk's 284. As you say Luetjens is very definite about some aspects, so if they identified a 50cm radar, I can't imagine that he would fail to inform the authorities ashore, especially when those authorities asked specifically to try and found out that data. I suspect that they were picking up pulses from one of the many 1.5 meters, 3.3 meters, or 7.5 meters radars, which the Germans already knew existed on patrol bombers and ashore.

Picking up the 7.5 meter radar pulses could have been quite feasable using the regular radio technology of 1941. Indeed Brown looks upon this as the more likely source for Luetjens assuming his ship was being painted by radar. Picking up and identifying decimetric and centimetric radar pulses required more advanced and more specialized technology. There's no question about this. German documents make clear that the Metox and the Samos could identify wave lengths to minimum of ~60cm (there is evidence that they could pickup the PRF of lower wave length radar). The Fanoe (a develpment of the Samos) that used a special "upper waving mixture", could pickup the wave lengths from 75cm to 20cm, but that came in 1943. Moreover, the antenna gear had to be revised to feed signals of such wave lengths to the Fanoe. Highly specilized gear needed to be developed to provide detection of the centimetric radars during 1943. The Metox's inability to pickup and identify wave lengths below 60cm was a factor in the severe 1943 losses suffered by the U-boat arm.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

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Re: What if Hood hadn't blown up?

Post by Vic Dale » Tue Mar 31, 2009 10:16 am

To Dave.

I think you have hit the nail on the head regarding frequency assessment. Of course Lutjens would have made some attempt to get this information back to SKL when it was clear the ship was doomed and enemy forces were around her. If it was not possible despite pulses being detected I think he would definitely have reported on it. That Group West did not pursue the question, indicates that they understood the reasons for the lack of such a report.

Signals pertaining to enemy radar are as follows;

0801 24/5 - "Two enemy radar sets recognised." (clear detection of radar then VD.)

2056 24/5 - "Impossible to shake off cruisers owing to radar."

Between 2300 and 2400. 24/5, a four segment transmission, probably the same message as contained in the "Long Signal" (also broken into four segments btw) and possibly transmitted again later that morning. There is a strong possibility that this message was passed in coded form to a U-Boat for repeat trasmission on Orders from Lutjens and containing a Fleet Security protocol so it would not be decoded before sending on.

However a signal from Group West, time segmented (0129 - 25/5) which would not have been recieved until approximately one hour later, read in relation to radar as follow;

" Determination of hostile DT frquency is valuable for future design of interference instruments."

At the time of reception, plus time to decrypt, Bismarck would have too little time to get that frequency due to Lutjens shaking the cruisers off at about 0230, taking account also of the fact that actual radar contact was intermittent due to zig-zagging.

Group West asking for the frequency strongly suggests that this was possible aboard the flagship and the fact that no frequency was transmitted to Group West, indicates that the ship was no longer receiving radar pulses. The enemy "maintaining surveillance" has to mean just that, they were searching and were still within reach of the passive underwater detection set GHG. On the premise that says; "If the enemy is in range then you too are in range" - Bismarck being able to detect them would also mean they could detect her, if they had similar equipment, which Brinkmann at least seems to think they possessed.

After 0230 on the 25th, Bismarck was safely in the blind sector astern of Wake-Walker's ships. So this above all else is the likely explanation as to why no frequency report was made regarding enemy radar.

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Re: What if Hood hadn't blown up?

Post by Dave Saxton » Tue Mar 31, 2009 1:57 pm

Nevertheless they could not know before hand the operating frequency of 600Mhz (50cm). The authorities ashore may have known that Bismarck possessed equipment good to 400MHz -500MHz (60cm) and may have suspected a deyployment of such radar and a detection may be expected. In any case if Bismarck had detection gear they would have identified one or many of the many metric radars such as Norfolk's 286, and that would not have been the big news like 50cm radar would have been. The PRF would have been 500hz -600hz for both.

What range could GHG still detect screw noise? The PG detected Holland's battle group shortly after 0500, so they would have still been about 20 N-miles away. By early on the 25th the distance would have been far greater and increasing. However, it was quite possible that transmitted pulses from Types 79, 279, and 281, which scanned 360*, could have still been picked up over a great distance. There is also the possibility of ASV MK-II pulses aboard patrol bombers being picked up over a great distance.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

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Re: What if Hood hadn't blown up?

Post by Vic Dale » Tue Mar 31, 2009 8:32 pm

To Dave.

There is a mind-set here around the whole Bismarck question which seems to insist that Lutjens was scared out of his wits by British radar. Yet on the morning in question, survivors reported that the sky was clear and blue and the wind was high, excellent conditions for observing stalking warships.

If Bismarck did pick up pluses from various radars at extreme range surface or airborn and concluded that this was their working range (masts down over the horizon) he would have been on the horn in the clear telling his chums at Group West they had practically lost the war, due to British Radar with extraordinary range capability. If we accept the assumption that Bismarck headed south east immediately after losing Suffolk, she would have been 230 miles away.

Lutjens made no such report and never even hinted at it. Radar is only mentioned 3 times in his signals and then more as a reinforcing report of what was learned earlier, in regard to the ability to refuel either ship unless the radar could be evaded by superior speed. He never mentioned it again after sending his report in the long message.

The ships which contacted him later were also carrying radar, yet there is no mention of this anywhere.

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Re: What if Hood hadn't blown up?

Post by Dave Saxton » Wed Apr 01, 2009 12:28 am

Hi Vic,


I'm only trying to present a likely explaination as to why Luetjens still thought that WW's shadowing force still maintained contact, and clarify some questions and ideas brought up pertaining to radar during the Denmark St and day after phase of the operation. The most likely explaination that Luetjens still thought he was being shadowed is the reception of radar pulses from a metric wave length radar.

The British were obviously beyond visual range, and also beyond a reasonable range for GHG when Luetjens sent these messages. If Luetjens thought that the enemy radar could be effective to "at least 35,000 meters" then it would be reasonable for him to suspect that they may be just out of sight over the visual horizon, if detection equipment was still registering radar pulses. This is actually quite possible with metric wave length radar. The radar pulses could have come from many sources including Tovey's battle group. von Muellenheim points out that Luetjens appears to have been so sure that the British maintained contact (he even said so in one message) that he saw no reason to restrict the use of his radio communications as late as 0852 or use the short signal procedure.

Obviously we can't be 100% sure, but the reception of metric radar pulses are the most plausible explaination in my opinion.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

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Re: What if Hood hadn't blown up?

Post by RF » Wed Apr 01, 2009 7:40 am

Another factor that is relevant, and nothing to do with radar per se, is the state of mind of Lutjens and his staff and crew in what was a very stressful situation, and the influence of that on Lutjens actions - including making the British radar seem more effective than it actually was.
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Re: What if Hood hadn't blown up?

Post by RF » Wed Apr 01, 2009 7:42 am

Dave Saxton wrote:Hence the long term response of the Kriegsmarine was an emphasis (if not an obsession) with improving the effective range of their radar equipment. Indeed later documents reveal that they placed high priority upon improved range performance especially with regard to radar directed long range gunnery aspects.
As far as I can see it didn't do the KM surface ships much good - for example at the Barents Sea fiasco, or in the last voyage of the Scharnhorst.
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