Bismarck pasive radar FuMB

[Pandora]

hello,
did Bismarck have pasive radar FuMB ?? to receive pulses from enemy active radars?
the absence of it could explain why Lütjens thought Bismarck was still shadowed on 25 May wehn contact had really been broken.
any thoughts?

[Dave Saxton]

The answer is: .....we don't know.

The Bismarck had none of the passive detector antennas such as the Timor, Samoa, and so forth that we find on the Tirpitz in some months hence (and a Bali is too small to show in photos). However, on unpublished, and uncensored, photos of Bismarck that I have seen, there is something like a Sumatra on the foretop gallery that may be a passive detector antenna.

The German Naval Research Lab (NVK) had passive radar detection receivers. These had been used as early as prior to the Battle of Britain to monitor British radar activity. If one of these was put aboard the Bismarck is not known. If doesn't show up on the manifest documents means nothing because of the great secrecy that surrounded all things radar.

Nevertheless, the Bismarck's regular communication radios could have been used to pick up and monitor much British radar activity anyway, as WWII radar expert L Brown wrote:

This incident (the long message) is linked to reports that Bismarck had a passive radar receiver and had monitored the tracking. If so it must have been an experimental set of which there is no record. and the passive receivers that first came into use more than a year later ( Brown was unaware of the existing NVK equipment when he wrote this in the context of the Metox) and would not have responded to 50cm waves (The Metox went to down 60cm and the Samos to 70cm). It is plausable that radio operators, presumably briefed on British use of long waves picked up on communication receivers some of the abundant 7.5 meter transmissions (Type 79 and Type 279) which they would have recognized as radar. Given the circumstances it is unlikely that they would have realized that this equipment (type 79 and 279 radars) was incapable of observing them at the ranges involved.

What Brown was unaware of at the time he wrote this was that Bismarck was equipped with specialized talk between ships equipment which operated on the decimetric wave lengths. Such as the GEMA FA70 with voice scrambling (this may be the device on the uncensored photos) and the Telefunken 50cm communications equipment (there was also UKW Telefunken and Lorenz TBS equipment). These equipment could have picked up Suffolk's (Type 284) and Norfolk's (Type 286) radar pulses.

Passive detection of radar pulses can not measure range from the source.

[Pandora]

thank you DAve Saxton
I have checked Rechbergs book again and he mentions a radar detector but doesnt say the type. I quote:
"Besides her three radar sets, the Bismarck had a radar detector, a simple receiver designed to pick up incoming pulses of enemy radar. upon receiving such pulses, the detector allowed the wavelength, the frequency and strength of the pulse, and the approximate direction of the sender to be determined. Precise direction-finding, however, was not possible."

do we know if Prinz Eugen had pasive radar at that time?

[Dave Saxton]

Von Muellenheim cites one of the radio operators on the Prinz Eugen on these questions:

*Hans-Henning von Schultz told the author in 1984: “The Prinz Eugen also was equipped with radar detectors. These passive radar sets, with which the beams of radio location set (radar pulses), could be detected in then a still inexact direction only.”

My thoughts on this are; first, Prinz Eugen was certainly equipped with radar detection gear by mid 1942, so is von Schultz remembering this and mistakenly ascribing this capability to May 1941 after the passage of many years? Perhaps he’s correct, because by 1942 the FuMB installations included the Timor phased array passive antenna array which could fix the exact direction of intercepted radar pulses. Therefore, if the equipment von Schultz is referring to was only capable of fixing an inexact direction, then he’s likely correct in his chronology.

This note was in relation to the question of if Bismarck was possibly picking up British radar after evading Wake Walker’s shadowing warships. von Muellenheim’s text reads:

I think that by 0700 on the 25th May our distance from the Suffolk, Norfolk, and Prince of Wales, must have been too great for us to pick up even weak pulses from them. … it is difficult for me to believe that radar pulses were still being picked up by the Bismarck at 0700.

Von Muellenheim would be right to be skeptical of radar pulses operating on decimetric or centimetric wave lengths still reaching his battleship. However, the Royal Navy operated much radar operating on meters length waves during this time frame. These meters wave length radars (Types 79, 279, 281, 286, and ASV I and ASV II…) transmissions could be picked up over great distances, despite not being able to receive target echoes back over such distances. Moreover, the Bismarck and Prinz Eugen would not necessarily of needed to use any special FuMB equipment to do so.

During the previous Operation Berlin by Scharnhorst and Gneisenau a special technical radar consulting team from the NVK, were embarked on Luetjen's flag ship. Did they already establish a precedent for bringing along the NVK FuMB gear?

[Antonio Bonomi]

Hello everybody,

since this is the period of Operation Rheinubung I take the occasion to ask an opinion : What was the real effect of the presence on board Bismarck of the FuMB 1 Metox ???

We are talking an early installation on Bismarck of the radar-detector METOX R600 ( passive detection ) used to intercept enemy radar transmission.

Bye Antonio

[Dave Saxton]

since this is the period of Operation Rheinubung I take the occasion to ask an opinion : What was the real effect of the presence on board Bismarck of the FuMB 1 Metox ???
We are talking an early installation on Bismarck of the radar-detector METOX R600 ( passive detection ) used to intercept enemy radar transmission.

Hi, Antonio
In my opinion we muddy the the waters by focusing on the Metox receiver. Metox was not the KM's first radar warning receiver nor its most capable. The KM had more capable warning receivers already by spring 1940. As it became obvious that the British were using airborne radar to locate surfaced U-boats, the French Metox company was contracted to mass produce a basic radar warning receiver to a design provided by the KM. It was intended to quickly equip U-boats with a radar warning receiver by mid 1942. The Metox was capable of detecting wave lengths down to 60cm.

At the same time the Germany company of Rhode und Schwartz designed and built the Samos detector. (It is incorrect that the Samos was a later improved version or a follow on to the Metox) Samos detected wave lengths down to 70cm. Both of these mass produced detectors became available by late 1941 or early 1942.

Did Bismarck have an alternative radar warning receiver to a Metox or Samos in may 1941? The answer is, yes, it could have. B-dienst had more capable radar warning receivers available. B-dienst's or the NVK's equipment were more capable than either the Samos or the Metox but these equipment were only available in small numbers. (B-dienst even logged a detection of 10cm radar in late 1941) But Bismarck didn't need a specially designed radar detector such as a Metox to detect British radar during 1941:
*The regular wireless comunucations receivers could have detected the transmissions of Type 79, 279, and 281.
*The more specialized talk between ships receivers could detect decimetric radar pulses if tuned to the right frequency.
* It has also been reported that Bismarck's FuMO27 radar receivers could have been used in listen only mode, but I'm rather sceptical that this would be done. The FuMO27 used a special tuning module which kept the receiver module perfectly aligned with its associated tramsmitter. The earlier models had missed detections in the past because of frequency misalignment between transmitter and receiver
*Finally, I have discovered evidence that the Bismarck likely had another specialized device aboard which could have detected radar, but I can not talk about it at this time.

[Dave Saxton]

: What was the real effect of the presence on board Bismarck of (radar warning capability)

This much we know. Luetjens reported that the enemy had at least two radars capable of tracking his battleship to 35km range. Group West asked that the frequencies of the enemy radars be logged.

Luetjens was wrong in his estimate that the enemy radar was effective to 35km (38,000 yards) The best preforming British radar at the time was Suffolk's Type 284 capable of tracking Bismarck to only 23km. However, in Luetjen's mind it meant the enemy had a more capable radar , and it would have made breaking backing back through a northern route more dicey. Luetjen's mistaken estimate went uncorrected and was a contributing factor of German officers incorrectly assuming that British radar was much superior even years later.