Scharnhorst Radar Set

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Alberto Virtuani
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Scharnhorst Radar Set

Post by Alberto Virtuani » Tue May 15, 2018 11:24 am

Hello everybody,

I'm trying to understand which was the late (1943 after "Cerberus") radar set of the Scharnhorst.

In addition to the FuMo27 (active radar, used for both gunnery and search , even if fixed in the rangefinder direction), fore and aft, was there any specific (air or surface) search radar on board ? I'm a bit surprised that Germans in 1943 had not clearly separated yet the tactical radar from the rangefinder gunnery radar and I would ask some clarification about the effectiveness of such choice......


Also which were the passive radars ? I know FuMb4 was on board (replacing the previous FuMb7) with a similar "Timor" antenna, but I think there were also dipoles around the main tower ("Sumatra"???) and a "Palau" antenna (2 additional dipoles) on top of the aft director. In same late photos I also see (very blurred image....) another antenna on top of the main director, possibly a "Bali" one. Is this correct ? Why all these passive radars ? Which were the corresponding radar sets used on board, apart from the antennas with their nice :wink: names ?

Many thanks for any advise.


Bye, Alberto
"It takes three years to build a ship; it takes three centuries to build a tradition" (Adm.A.B.Cunningham)

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Dave Saxton
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Re: Scharnhorst Radar Set

Post by Dave Saxton » Tue May 15, 2018 3:52 pm

Scharnhorst was equipped with two new FuM027 sets during its stay at Brest. One at the foretop and one at the aft rangefinder. Prior to that it had only one FuMO22 set at the foretop.

Also during the Channel Dash, Scharnhorst was equipped with a Timor passive antenna (FuMB7) on the back side of the foretop opposite of the FuMO27 antenna. The Timor was 4x2 meters, same as a standard Seetakt antenna, and it is mistakenly labeled as a FuMO27 on Tirpitz in many books. The Timor would have served a Samos passive receiver. It is also possible that there may have been Bali omni directional passive antennas serving the Samos as well, but these are so small that they would require incredibly resolute photos to be seen. These would be mounted on mast heads or yard arms. I have not seen any Sumatra antennas in photos prior to and during the Channel Dash.

After the Channel Dash, and prior to it redeploying to Norway, the passive radars were significantly revised. The Timor was relocated to the front of the foretop range finder below the FuMO27 antenna, with the FuMO27 antenna moved higher up. It now had Sumatra antennas positioned each on all four hand rails around the foretop gallery and on the aft mast's tripod railings. Bali antennas are located on the mast heads. A Palau passive antenna was mounted on top of the aft rangefinder. These passive antennas arrays would have served passive receivers, probably Samos each. The Palau would have served a Wanze passive receiver.

After the mission to bombard Spitzbergen, and Prior to Northcape, the FuMO27 sets were both replaced with FuMO26 sets. The foretop position received a 3 x 6.5 meter, horizontally polarized, common mode antenna. The Timor antenna was removed. The removal of the Timor probably indicates that the Scharnhorst was now equipped with at least one new centimetric radar detector. The aft FuMO26 was equipped with a 2 x 6.5 meter antenna with vertical polarization.

Some books and articles report that Scharnhorst was also equipped with a FuMO60 series Hohentwiel antenna to the foremast at this time but I have found no confirming evidence of this.

It is true that Seetakt was a multi role radar system. The main difference between it and the corresponding Freya air warning radar was the wavelength. Freya was one of the best air warning radars of WW2, so Seetakt would have been very capable in that role. There was no need to find space on board the ship to deploy a Freya. The FuMO26 designation designated that it was a version that was also capable of flak direction. Seetakt was capable of blind fire surface gun laying beginning during 1940.
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: Scharnhorst Radar Set

Post by Dave Saxton » Tue May 15, 2018 8:07 pm

Alberto Virtuani wrote:Why all these passive radars ? Which were the corresponding radar sets used on board, apart from the antennas with their nice names
There were so many passive antennas because the primary passive detection antenna was omni directional. It was omni directional so it could sound the alarm if a directional antenna was not aimed in the correct direction, or aimed in the correct direction at the correct time in the case of a rotating enemy radar beam. Since the Bali was omni directional it could not indicate from which direction the radar pulses were coming from. The Sumatra antennas were therefore positioned, one each, on the four sides of the foretop to indicate a general direction the pulses were coming from. Then the directional Timor or Samoa antennas could be used to determine the direction within one or two degrees that the pulses were coming from.

The receiver on the other end of the cable from these antennas was in most cases, with surface ships, one or more Samos receivers. The Metox may have also been used in some cases. The Wanze was a receiver that automatically cycled through a range of possible enemy radar wavelengths continuously. It was usually used in conjunction with the Palau on large surface ships.

The fatal flaw of this passive detection system was that it could not detect wavelengths of less than about 70 cm. For example, when the Hipper was using it's active radars to shoot at enemy destroyers at Barents Sea the passive detection system provided no warning of the approach of Adm. Burnette's cruisers, because the enemy was using radars operating at wavelengths the system could not detect.

By the fall of 1943 early centimetric radar detectors were being deployed on an emergency basis to fleet units and U-boats. However, these early centimetric detectors were notoriously unreliable and had very poor bearing accuracy. This is the most likely reason Scharnhorst was caught by surprise by Burnette's cruisers at the first skirmish during Northcape. Scharnhorst was detecting enemy radar pulses throughout the day, nonetheless.

By 1944 a much better centimetric detector was available in the form a series two Naxos. The Naxos rotated two plastic cone antenna elements (like on the USN Mk8) around and around at high speed inside of a radome. It was both omni directional and directional with a PPI like indicator. Too late to help Scharnhorst at N. Cape though.
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: Scharnhorst Radar Set

Post by Dave Saxton » Tue May 15, 2018 8:20 pm

I don't use the FuMB numbers system to identify KM passive radar equipment. I only use the code names for antennas and receivers. The number designations will contain duplications. Antennas were given a FuMB number and also receivers were given FuMb numbers, each list starting with one. It can be very confusing.
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: Scharnhorst Radar Set

Post by Dave Saxton » Tue May 15, 2018 8:35 pm

Alberto Virtuani wrote: I'm a bit surprised that Germans in 1943 had not clearly separated yet the tactical radar from the rangefinder gunnery radar and I would ask some clarification about the effectiveness of such choice......
Throughout 1943, the KM was waiting for the Berlin PPI radars. Although Seetakt was quite capable of performing each of its multi-role tasks well, Barents Sea exposed the problem of the radar not being able to perform each role simultaneously. The Hipper was caught by surprise by the approach of enemy cruisers while the radars were preoccupied by shooting at enemy warships in a different direction.

The need for a PPI tactical radar became glaringly apparent. That radar was Berlin. It was deployed by the Spring of 1944. Once again too late to help Scharnhorst.
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: Scharnhorst Radar Set

Post by Alberto Virtuani » Wed May 16, 2018 10:34 am

Hi Dave,
so many thanks for your answers ! Three more points, if I may:
you wrote: "Seetakt was a multi role radar system"
If I understand correctly, this means that Seetakt was able to search surface targets, provide rangefinding for gunnery and also perform air surveillance.
However, I don't understand how this could be done by a flat antenna: I imagine the whole rangefinder (armored aft) had to be rotated continuously to perform such search, and also that this antenna had a quite large lobe vertically to allow an horizontal antenna to cover also high altitude flying airplanes. Is my understanding correct ?


you wrote:"Sumatra antennas positioned each on all four hand rails around the foretop gallery and on the aft mast's tripod railings"
Were the Sumatra antennas positioned around the squared top of the main director or on the hand rails of the "Vormars" ? I was thinking they were in the same position as in Tirpitz, that is around the director.....
Do you confirm they were 4 around the Vormars and how many around the main mast railings ?
Are the sumatra the "butterfly" dipoles like these (my very bad drawing...)
Sumatra.jpg
Sumatra.jpg (1.42 KiB) Viewed 934 times
you wrote: "After the mission to bombard Spitzbergen, and Prior to Northcape, the FuMO27 sets were both replaced with FuMO26 sets."
Are you sure about that ? I have never seen any photo of Scharnhorst with such a large antenna (do you have any?), Tirpitz received FuMo26 only in april 1944 (AFAIK).... :think:

Thanks again !

Bye, Alberto
"It takes three years to build a ship; it takes three centuries to build a tradition" (Adm.A.B.Cunningham)

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Re: Scharnhorst Radar Set

Post by Dave Saxton » Wed May 16, 2018 2:44 pm

Alberto Virtuani wrote:Hi Dave,

If I understand correctly, this means that Seetakt was able to search surface targets, provide rangefinding for gunnery and also perform air surveillance.
However, I don't understand how this could be done by a flat antenna: I imagine the whole rangefinder (armored aft) had to be rotated continuously to perform such search, and also that this antenna had a quite large lobe vertically to allow an horizontal antenna to cover also high altitude flying airplanes. Is my understanding correct ?
It would depend on how far away the aircraft are as to what height it could pickup high flyers. It was probably much like the situation with the American SK. As aircraft got closer until they were right over head it could not detect high flyers anymore. The longer, meters length wavelengths, used by Freya and the British air warning radars worked better for the task of air warning. Meters wavelength radar has a vertical lobe structure and multiple lobes. High flyers can be picked up as they pass through each lobe structure in sequence. This also allows their altitude to be estimated without actually measuring it. It also means they can not pickup wave top height flyers at longer ranges. However, the advantages of Freya was not worth the disadvantages of finding the space for one on board ship for such a large and heavy radar set.

The rangefinders could be set to go around and around continuously in the same direction at a slow rate for continuous sea surveillance. They could also be traversed rapidly when tracking aircraft. I have seen some movie footage of Tirpitz's rangefinders tracking relatively high speed, low flying, aircraft. However, it was not ideal to use the Seetakt mounted to the rangefinders in a continuous rotation mode. A small antenna mounted to a mast, or a radome like used by Berlin, was better.
Were the Sumatra antennas positioned around the squared top of the main director or on the hand rails of the "Vormars" ? I was thinking they were in the same position as in Tirpitz, that is around the director.....
Do you confirm they were 4 around the Vormars and how many around the main mast railings ?
Are the sumatra the "butterfly" dipoles like these (my very bad drawing...)
Sumatra.jpg
Both. I have seen photos of Scharnhorst that feature Sumatra antennas on both the hand rails and on the foretop rangefinder sides.

Yes, the Sumatra antenna is the butter fly shaped dipole. The same dipoles make up the Timor array too. The Timor array consisted of a row of those butter fly shaped dipoles arranged vertically, and a row arranged horizontally, mounted to a 4 x 2 meter mattress.
Are you sure about that ? I have never seen any photo of Scharnhorst with such a large antenna (do you have any?), Tirpitz received FuMo26 only in april 1944 (AFAIK).... :think:

Thanks again !

Bye, Alberto
Yes, I have a photo that shows a 3 x 6.5 meter antenna forward, and another photo that shows the 2 x 6.5 meter antenna aft. Moreover, primary documents clearly state that Scharnhorst was equipped with brand new FuMO26 sets, and that the trials carried out in the fjords confirmed the performance and accuracy attained by the Prinz Eugen FuMO26 trials. Even the narratives of the Battle of N. Cape by survivors describe the forward radar antenna that was carried away by the Norfolk hit as a "new" installation.

Tirpitz had its FuMO26s installed by March 1944. There was no hurry to get the new radars on Tirpitz before 1944 because it was immobilized and under going repairs.
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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Alberto Virtuani
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Re: Scharnhorst Radar Set

Post by Alberto Virtuani » Thu May 17, 2018 1:04 pm

Hi Dave,
again many, many thanks for your clarifications.
you wrote: "Yes, I have a photo that shows a 3 x 6.5 meter antenna forward, and another photo that shows the 2 x 6.5 meter antenna aft. Moreover, primary documents clearly state that Scharnhorst was equipped with brand new FuMO26 sets"
The only image I have after Sizilien operation is a quite bad quality one (here a detail only:
Scharnhorst_in_Langsfjord.jpg
Scharnhorst_in_Langsfjord.jpg (79.72 KiB) Viewed 891 times
In this one I see the fore and the aft tangefinder and no antenna (apparently) on the fore, just a possible shadow on the aft one but, comparing with the 10.5 meters rangefinder, I would not say it is a 6.5 meters one.....

I happily trust you about this last radar set modification on Scharnhorst. :D


One last question: were the FuMo26 antenna patterns (aft and fore) like he ones depicted in this drawing, despite the top one is called FuMo25 ?
FuMO26.jpg
FuMO26.jpg (108.76 KiB) Viewed 889 times

Bye, Alberto
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Re: Scharnhorst Radar Set

Post by Dave Saxton » Thu May 17, 2018 2:58 pm

The new radars sets were installed after Operation Sizilien, exactly when I don't know. I would expect before the end of Nov, before the onset of the Polar Night, which lasted until the end of Jan, because the photo I have a copy of was not taken at night.

According to the documents the aft set received the 2 x 6.5 M antenna so they could compare how the new sets performed using vertical polarization vs horizontal polarization. Strictly speaking, the 2 x 6.5 M antenna with vertical polarization was FuMO25 when installed on the Destroyer Pole mounting system. The FuMO number system did not yet exist at that time. It came later during late 1944 and was applied retroactively. Maybe even post war. The documents don't identify the radar sets by FuMO number but only speak of 3 x 6, or 2 x 6, 2 x 4.... meters, or if the Zerstroyer Saul, or rangefinder, mounting was used.
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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Alberto Virtuani
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Re: Scharnhorst Radar Set

Post by Alberto Virtuani » Thu May 17, 2018 3:17 pm

Hi Dave,
thanks !

Bye, Alberto
"It takes three years to build a ship; it takes three centuries to build a tradition" (Adm.A.B.Cunningham)

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Re: Scharnhorst Radar Set

Post by Alberto Virtuani » Sat May 19, 2018 10:04 am

Hi Dave,
would you mind giving me some references about the German sources that testify the installation of the FuMo26 on Scharnhorst in November 1943 and let me know from whom I could possibly get the photos of Scharnhorst with these installation fore and aft ? I have looked again in all my books/documents and I couldn't find any....

Thanks in advance

Bye, Alberto
"It takes three years to build a ship; it takes three centuries to build a tradition" (Adm.A.B.Cunningham)

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Re: Scharnhorst Radar Set

Post by Dave Saxton » Sat May 19, 2018 8:04 pm

The documents are from the OKM Tagung, Berlin, March 1944.
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: Scharnhorst Radar Set

Post by Alberto Virtuani » Sun May 20, 2018 7:55 am

Hi Dave,
thanks a lot, I will try to get them.


Bye, Alberto
"It takes three years to build a ship; it takes three centuries to build a tradition" (Adm.A.B.Cunningham)

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