Bismarck radar detector

[wadinga]

Hi Herr Nilsson, Byron and Hans,

The 06:54 is because the Scarborough D/F station was using local British time zone Zulu, Greenwich Mean Time (or UTC if you are American) Luckily for comprehension both RN and Kriegsmarine were using Zone Bravo time ie + two hours on GMT,suitable for central Europe, even way out west which is why Victorious' attack took place at 24:00B but in daylight . So 06:54Z becomes 08:54B, 07:48Z becomes 09:48B and coincides nicely with the German records.

Whatever time it was transmitted, it provides situation at 07:00. As Mr.Nilsson said, it is at 07:00 that Lütjens thought to be shadowed by CS1.

We know when it was transmitted because Scarborough intercepted it. What would be the point of reporting what was happening tactically in a highly dynamic and critical moment, but nearly two hours out of date, when Bismarck had covered 40 plus miles since 07:00? Presumably editing the message with a new UHR would require a restart of the bureaucratic process.

Lutjens' later wordy report was so long it was broken up into four separate segments transmitted separately in order to make decoding (by the British) even more difficult. Even with Enigma, the longer a message was, sent with the same settings, the more likely it could be broken. (thanks to Tommy 303 for this info, very knowledgeable, sadly haven't seen him posting recently).

We don't know if Bismarck got radar emissions but, during attempt to break contact, radio silence has not to be explained: it is due by definition.

So the justification for breaking radio silence at 08:55 was that "breaking contact" manoeuvre was not being done any more? The distance between any element of CS1 and Bismarck had increased continuously from about 11 miles around 03:00 to whatever at 08:55. If radar emissions were being detected at all from Wake-Walker's distant ships- extremely unlikely due to their low transmitting aerials, their strength would have been diminishing for hours.

Any thoughts from other posters?

All the best

wadinga

[hans zurbriggen]

Hello Mr. Wadinga,
many thanks for the clarification about timing. Still I agree also with Mr. Nilsson that timing is sometimes confusing.

'So the justification for breaking radio silence at 08:55 was that "breaking contact" manoeuvre was not being done any more?'

The manoeuvre (circle) was over and Lütjens staff considered at some point in time that it had not been successfull. We don't know exactly when, but timing reported by Lütjens (07:00) points to this moment. In daylight, with scarce fuel, any further attempt was possibly pointless, in his view.

hans

[Herr Nilsson]

Actually we don't know anything about Bismarck's movements at all.

[hans zurbriggen]

Hello Mr. Nilsson,
we have to rely (as in other cases) on British drawn Bismarck' track, defined by Tovey as 'probably reasonably accurate', matching Baron account.

hans

[Dave Saxton]

If I recall correctly, back in 2013 I was examining some commentary by Helmut Giessler about documents (which no longer exist) he had access to during the war on these matters.

Giessler began his commentary on this specific issue by stating that it is no longer possible to know with certainty if Bismarck had the means to detect enemy radar pulses. He informs that the author of the document assumed that Bismarck did have a prototype device onboard, but that the author's assumption could not be confirmed.

Nonetheless, Giessler continued on that it was possible that Bismarck had such a device because there was such a experimental device developed at the time. Furthermore, Giessler stated that the device was equipped with a special broadband antenna which allowed it to pickup all the necessary wavelengths, although the directional accuracy would have been very poor. The device had been developed in part from examination of a British radar set the Kriegsmarine recovered intact on the Channel Coast in mid 1940. The author of the document assumed that this device was installed on Bismarck. So it was possible, perhaps even probable, but it cannot be proven. Giessler added that it was not often understood (probably not by Luetjens at the time) that radar pulses can be picked up by a passive device at least double the distance that the pulses can travel to the target and back to the receiver and still be registered.

Another interesting aspect about Giessler's commentary was that the author of the documents investigated if the Swordfish found Bismarck, in both cases, by radar. The author had been informed by a British officer (a POW?) that the Swordfish had no radar at that time and that they had been directed to Bismarck's location by cruisers. The author had agreed with this explanation. However, Giessler's own comment was, " A remarkable accomplishment!" which I take to be that Giessler remained skeptical. Indeed according to Brown, some of the Swordfish on both carriers were equipped with ASV II, and they had located Bismarck by radar. This raises the question that if Bismarck had such a device, if it picked up distant transmissions from airborne radar?

[hans zurbriggen]

Hello Mr. Saxton,
welcome to this 'radar' discussion: having read most of your posts on this forum, I hope you can answer some questions, if I may ask.

Are you still thinking Bismarck had a passive radar detector on board and are you now in position to tell us which antenna was used ? Why did you concur in 2013 with Giessler (speaking about a prototype), instead of thinking to an available (possibly NVK modified) Metox R600 ?
Reading G.Hepke and E.Ludwig, I understand Metox R 600 was available already in 1941. Ludwig accounts for quite a broadband (see below) covering metric and decimetric wl's (thus detecting Type 284 and Type 286 emissions, but apparently not Type 279 and Type 281). Is this correct from a technical viewpoint ?

Metox R600 bandwidth.jpg (30.94 KiB) Viewed 1561 times

Regarding the 'Feindiche Ortung' document, it looks like in June 1941 KM deployed to all big ships a passive radar detection system (starting with Lützow). I understand this was Timor + Sumatra(s) antennas and a receiver for wl's 50 to 200 cm (closer to Metox practical band than to Samos, available only from 1942). Was Metox the 'standard' device deployed to KM ships (including Tirpitz in September) or which was receiver used ?

If this is the case, why did Kriegsmarine prefer Samos to Metox in 1942 ('limited' band from 90 to 470 MHz), unable to pick up Type 284 emissions, maintaining this handicap until 1943 end ? Was it due to bad directionality of Metox ?


hans

[wadinga]

Hello All,

Very pleased to hear from you Dave.

The author had been informed by a British officer (a POW?) that the Swordfish had no radar at that time and that they had been directed to Bismarck's location by cruisers.

This is definitely wrong. ASV Mk II Swordfish were aboard both Victorious and Ark Royal and used their radar to locate Bismarck in overcast squally conditions. John Moffat, a pilot from the Ark says in his book "I Sank the Bismarck" (OK an exaggeration) that the abortive strike against HMS Sheffield located the target through solid cloudbase at 600ft at 20 miles. Much better performance against a 10,000 ton cruiser than a surfaced U-boat and Bismarck was a bigger radar target still. The strike flew at 6,000ft above cloud in an icing zone.

If Victorious search on the 25th flew at 6,000ft with ASV on, how far away would the signal be detectable even if no returns were picked by the plane?

All the best

wadinga

[Dave Saxton]

Are you still thinking Bismarck had a passive radar detector on board and are you now in position to tell us which antenna was used ?

I concur with Giessler that it cannot now be determined but I think it as probable. I don’t know what antenna may have been used if that was the case. There are no photos of Bismarck showing a Sumatra, or similar production antenna that I know of.

Why did you concur in 2013 with Giessler (speaking about a prototype), instead of thinking to an available (possibly NVK modified) Metox R600 ?

I do not discount the possibility of a Metox.
Also Metox may have been used on several surface ships for period before being superseded by Samos.
I tend to put some weight to Giessler’s views because he was there, and in a position to know, however.

Ludwig accounts for quite a broadband (see below) covering metric and decimetric wl's (thus detecting Type 284 and Type 286 emissions, but apparently not Type 279 and Type 281). Is this correct from a technical viewpoint ?

According to primary documents the Metox detected wave lengths to minimum of 60cm. If it picked up higher frequency harmonics as stated by Ludwig then the same would likely apply to Samos. According to the documents Samos detected down to 60cm and up to beyond the 330cm range, making it able to pickup Type 281.

If this is the case, why did Kriegsmarine prefer Samos to Metox in 1942 ('limited' band from 90 to 470 MHz), unable to pick up Type 284 emissions, maintaining this handicap until 1943 end ? Was it due to bad directionality of Metox ?

The receiver usually used with Timor and Sumatra…ect was the Samos which was more capable or at least as capable as the Metox, plus the directional capabilities were superior. Later war, an improved Samos called Fano replaced the Samos, although it may have still been referred to as a Samos by those not in the know. Often devices were referred to by the manufacture's name, rather than the code name. The range of Fano was 70cm down to 15cm. The 70cm range up to 330cm was taken over by the Wanze receiver. The Wanze automatically monitored all the frequencies in that range, without needing to be manually tuned.

By that time the emphasis for passive devices was detection of centimetric wave lengths. The first such device, the Naxos was a stop gap device of limited capability. The directional accuracy reportedly was poor. Later the Tunis superseded it. Tunis was quite a good piece of kit, capable of reliable detection of 15cm to 3cm and less with very good directional accuracy.

[Dave Saxton]

If Victorious search on the 25th flew at 6,000ft with ASV on, how far away would the signal be detectable even if no returns were picked by the plane?

All the best

wadinga

Good question.

[wadinga]

Hello Dave,

Well Kurt Fricke provides an answer of sorts in Feindliche Ortung- the Top Secret document collating how Bismarck might have been tracked which makes no mention at all of a detector in Bismarck:

(Excuse the web-based translation)

Several weeks ago, it became known through an agent follow-up that the British maritime reconnaissance aircraft should have an apparatus that allows them to fly to ship targets up to 100 nm away. Tests requested by the High Command of the Kriegsmarine by the German Air Force with a Dete device provisionally installed in the aircraft have resulted in ranges of 60 km at medium altitude. A British recently emergency landing long-range reconnaissance aircraft had the almost intact device on board, it resembles the German Em III device, the wave used is about 1.60 m, the limit of the range scale is actually 100 nm.

A calculation according to the formula of optical vision shows that in the presence of a sufficiently powerful transmitter, an aircraft at an altitude of 2200 m can achieve Dete ranges of 100 nm = 185 km against a battleship target.

That 7,200ft. However this theoretical result doesn't seem to take into account that the impulse has to be strong enough to be detected back at the aircraft. It's probably a considerable over estimate of even one way propagation.

BTW remember when we were trying to figure out what EM III might be?

All the best

wadinga

[hans zurbriggen]

Hello Mr. Saxton,
many thanks for this valuable information.
If I understand correctly, 3nd and 4rd 'harmonics' usage is unable to practically pick up emissions, thus Metox actual sensitivity against radars is limited to 'fundamental' and 2nd 'harmonic'. Referring to detailed Metox R600 technical specifications reported by Ludwig (see above post), practical bandwidth (against radars at least) is therefore limited to 113 to 480 MHz (62.5 - 265 cm).
If this is the case, it is clear why KM in 1942 opted for Samos that covered up to 330 cm, loosing only 60 to 70 cm band (where no British radar was operating) and getting a better directionality.
Curious, however, that Ludwig (who studied Metox R600 in detail, taking it apart, repairing (using original parts) and reassembling it), even describes how it should have been used in order to detect the Type 284 radar:

Metox R600_ Type 284.jpg (83.91 KiB) Viewed 1508 times

Is this actually impossible due to practical sensitivity in the 3rd and 4th 'harmonic' bands that makes it unable to detect radar emissions ?


I do not yet understand why you refer to Metox and Samos as alternative receivers: Metox model R600 was available since 1941 (or even 1940), while Samos became available in 1942 only. Therefore, in summer 1941 KM should have been 'forced' to deploy Metox R600 to big ships (or another 'prototype' developed by NVK), waiting 1942 for 'upgrading' to Samos: is this correct ?

Thanks also for clarifying Wanze automatism + its complementarity to Fano, in order to cover a larger bandwidth than Samos (in 1943 only, is my understanding correct ?).

hans

[wadinga]

Hello All,

we have to rely (as in other cases) on British drawn Bismarck' track, defined by Tovey as 'probably reasonably accurate', matching Baron account.

Looking at a chart, based on Bismarck's estimated track, at 08:00/25 (being somewhere between 07:27 and 08:55) Bismarck was 120 n miles away from both Norfolk and Suffolk and 100 n miles away from PoW. Which of these above-named systems might allow Bismarck to pick any of these shipboard transmissions at such huge distances and especially all of them so as to be able to reliably identify the individual transmitters?

If some system had been monitoring British shipborne radar transmissions throughout the night, as the ranges extended out towards 120 miles, when might the operators have noticed one or more had disappeared completely?

Of course when the segments of the "long-winded" signal were actually sent, since Bismarck and her pursuers were heading in radically-different directions the range from them was much more than 120 miles.

Is the equivocal Giessler source on a radar detector in Bismarck his book Der Marine-Nachrichten- und -Ortungsdienst - Technische Entwicklung und Kriegserfahrungen pub 1971?

Working together to find the best fit for reality.

All the best

wadinga

[hans zurbriggen]

Hello Mr.Wadinga,
Bismarck position at (or immediately before) 07:00 (timing specified in Lütjens message), was roughly 70 (PoW) to 90 (SF) nm from CS1 ships (https://www.kbismarck.org/forum/downloa ... hp?id=3894). Emissions go much farther than radar range.
BS could in no way hear airplanes emissions before their take-off at 08:10 (very unlikely she could even after, due to their course opposite to BS direction), thus no relation of airborne radars with 07:27 message. Their radar frequency was different from any CS1 ship too.

hans

[wadinga]

Hello Hans,

Have you considered the so-called "radar horizon"? Radar signals are of line of sight only, unless there is anomalous propagation, so the curvature of the Earth would make signals transmitted from the masthead of one ship invisible even to the masthead of another at 70-90 miles. CS1 and PoW were
"below the radar horizon" from Bismarck, even at 07:00.

However because there was no point in reporting what had been happening at 07:00 when the radio report actually went out at 08:55 (ie nearly two hours later) it seems likely to me that maybe a stray transmission from a Swordfish leaving Victorious was picked up, misinterpreted as coming from shadowing ships and the 07:27UHR was modified with erroneous information. BTW did you know that the Type 286P installed in Norfolk was actually exactly the same as the ASV II airborne radar with the same approx 1.5m wavelength?

All the best

wadinga

[hans zurbriggen]

Hello Mr. Wadinga,
while atmospheric conditions may unpredictably bend elecromagnetic waves downward due to refraction, increasing radar horizon, imho it's impossible (using this chart scale and available detail) to determine whether BS was over or under the radar horizon at 07:00. A different radius/shape of Lütjens' circle might 'bring' BS much closer (even 40 nm) to CS1 ships at 07:00.
I am afraid that Lütjens' message (at whatever time prepared/transmitted) explicitely specifies a situation at 07:00. This excludes airborne radars.

hans


edit: afaik Type 286 used 214 MHz while Mark II used frequency 176 Mhz instead of 214 Mhz after mid 1940. Same radar set though.