Tirpitz' Radar

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Tirpitz' Radar

Postby Bgile » Wed Sep 03, 2008 12:33 am

I made the mistake of posting on Bob Henneman's forum that I thought the radar on Tirpitz might have been as good as contemporary US Radar. They immediately challenged me to dig up where I had heard that and gave a couple of references showing cookie cutter statements to the effect that German officers didn't understand radar and that it wasn't as good, including Friedman.

I can't find the post I was looking for. I think it was by Dave Saxton. Can someone point me at it? It was his belief that Tirpitz had more advanced and redundant systems than Scharnhorst, for example.

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Re: Tirpitz' Radar

Postby Dave Saxton » Wed Sep 03, 2008 7:56 am

Hi Steve,

I can well imagine that such statements will get challenged. The GEMA radars are not well understood and many of the details are not commonly known. I don’t recall posting a detailed report on the Tirpitz’s radar capabilities. I’m not yet prepared to go public with all of my findings yet, but I'll try to throw you a few bones in the interim.

In 1942, when the ship transfered to Norway, Tirpitz was equiped with three GEMA active radars, and several passive devices. The active radars used by Tirpitz were the second generation GEMA models with TS6 transmitting triodes. These decimetric radars compared well with the decimetric radars used by the Allies during the 42 through 43 periods, such as Mk3 (FC) and Type 284. These GEMA radars were used for both tactical use (such as search, surface warning, air warning, navigation, station keeping...ect...) and gun laying.

For general tactical radars, the Allies had by 1942 the centimetric Type 273 and the SG. The British Types 271 and 273 gave the British radars more or less equal capability to Seetakt in those roles- that the British previously lacked. SG was centimetric, and had PPI, but it wasn’t more accurate than Seetakt. For example, SG had a resolution for range of 500 yards on the PPI, and 300 yards on the A-scope. Seetakt at that time had a typical resolution for range of 100 meters, depending on how much the fine range indicator had to be zoomed in or out.

The American Mk3 for gun laying, was fairly accurate, but it’s range resolution was inferior, (to both German and British decimetric radars) and it had an usually wide horizontal beam width while lobe switching. Lobe switching was of course required to fix the bearing accurately enough for blind fire, and operators were instructed to always use lobe switching.

I just haven’t found a large disparity in radar capabilities during this (1942-43) period between the Allies and the Tirpitz.

Following the raid on Spitzbergen, during the period when the Tirpitz was laid up, the Tirpitz radars were upgraded. The GEMA radar locations received new extra large antenna variants, there was an additional new Lorenz Hohentwiel radar provided for general tactical use, with the antenna stepped on the foremast, and there was a Telefunken Wuerzburg flak direction radar added. The capabilities of this set of radars did not compare badly.

For gun laying, Seetakt was regarded as accurate enough if it could obtain the required range.

The new large antenna GEMA radars for fire control were proven in extensive trials to be more than accurate enough in both distance and side to side measurements. It was expected that the larger antennas would provide a 30% increase in effective range. The performance specifications for accuracy given in documents compare very favorably.

In autum 1944 the Prinz Eugen first received the Berlin (FuMO81) tactical radars with multiple PPI, and Tirpitz may have received this as well in place of the Hohentwiel by September or October. Had Tirpitz survived into 1945, there is little question that Tirpitz would have had, with certainty, the Berlin equipment operating on 6cm or 9cm, as well as 3cm Euklid equipment to bolster the Wuerzburg , and additional 125kw Seetakt tactical models. Such a radar suite would not have compared badly.
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: Tirpitz' Radar

Postby RF » Wed Sep 03, 2008 8:05 am

Given the lack of attack opportunities afforded to the Germans at that time I suppose it would make real comparison with Allied radars more difficult - the German systems not really being put to the test.
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Re: Tirpitz' Radar

Postby Bgile » Wed Sep 03, 2008 3:44 pm

Thanks, Dave. :)

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Re: Tirpitz' Radar

Postby Dave Saxton » Sat May 14, 2011 3:09 pm

Dave Saxton wrote:.....In autum 1944 the Prinz Eugen first received the Berlin (FuMO81) tactical radars with multiple PPI, and Tirpitz may have received this as well in place of the Hohentwiel by September or October. Had Tirpitz survived into 1945, there is little question that Tirpitz would have had, with certainty, the Berlin equipment operating on 6cm or 9cm, as well as 3cm Euklid equipment to bolster the Wuerzburg , and additional 125kw Seetakt tactical models. Such a radar suite would not have compared badly.


Well its official, upon further research into my soon up coming book it is now proven that Tirpitz was equipped with a FuMO81 Berlin S centimetric surface surveilence radar, in addition to the FuMO63 Hohentwiel K search radar, by spring 1944. This fitment occured even before the Prinz Eugen was equipped with Berlin. The Berlin S radar operated on a wavelength of 5.8cm and utilized multiple PPI indicators. In addition to a master PPI for the radar operators, additional indicators could be supplied to other command stations about the ship. This way situational awareness for the ships command could be gained at a glance. The PPI's could be set up with 18km of range displayed or 60km of range displayed. Power output of Berlin S was 15kw with a range to destroyers of 30km. This range is comparable to contemporary SG-II or the Combination Radar Types 293/277. Range accuracy was 100 meters and range resolution was 125 meters. Bearing resolution was 2 degrees.

The Hohentwiel K was not replaced by the Berlin, but the Berlin was added to the overall radar suite on Tirpitz. The Hohentwiel K had an illumination energy of 100kw and the antenna was mounted to height of 35 meters. Range to a destroyer was 36km according to Beckh. The Hohentwiel may have been equipped with PPI indication as well, because GEMA sub contracted their PPI technology to Lorenz during 1943.

The FuMO26 firecontrol radar on PG was apparently equipped with the option of using a 125kw transmitting module with anode modulated TS60 transmitting triodes if greater range was needed. This was likely also the case with Tirpitz's three FuMO26 sets as well. The FuMO26 already compared favorably with late war Allied firecontrol radar in terms of accuracy and overall capability. With the 125kw option, battleship to battleship range could be extended to 60km.
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: Tirpitz' Radar

Postby dunmunro » Sat May 14, 2011 7:15 pm

What did the antennae look like?

It seems odd that Scharnhorst would not have received a similar set, unless it was fitted to Tirpitz after the loss of Scharnhorst.

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Re: Tirpitz' Radar

Postby Dave Saxton » Sun May 15, 2011 3:17 am

Berlin S did not use a conventional antenna. It was a small plastic radome. It was not yet available in Dec 1943, but was apparently only a couple of months away.
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: Tirpitz' Radar

Postby Bgile » Sun May 15, 2011 7:07 am

Dave Saxton wrote:Berlin S did not use a conventional antenna. It was a small plastic radome. It was not yet available in Dec 1943, but was apparently only a couple of months away.


They did all that with a small plastic radome? And today we need a large rotating antenna about 4 to 6 feet across depending on the version? They must have been way ahead of where we are in the 21st century. Our FC antennas are dishes about 4 feet across ( a guess ).

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Re: Tirpitz' Radar

Postby Dave Saxton » Sun May 15, 2011 1:57 pm

Bgile wrote:They did all that with a small plastic radome? And today we need a large rotating antenna about 4 to 6 feet across depending on the version? They must have been way ahead of where we are in the 21st century. Our FC antennas are dishes about 4 feet across ( a guess ).


You misunderstand. Berlin was a surface search (general tactical) radar with PPI indication like SG. It was not a firecontrol specific radar system. SG used a small cut parabolic reflector (looks like a blade) with a single dipole at the focus. Inside the Berlin radome were plastic cones like those used by MK8, and they were spun around at several hundred revolutions per minute with a 1250 pulse repetition rate. The latewar German naval firecontrol radars were the FuMO26/34 with very large phased array antennas featuring no less than 64 full wave dipoles. And yes, in some ways and some aspects they did have highly advanced radar technology for the time period.
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: Tirpitz' Radar

Postby Bgile » Sun May 15, 2011 3:06 pm

You are correct ... I did misunderstand and confused two types of radar in your sentence. What was the range of Berlin against a destroyer size target? Most modern surface search radars are much larger and rotate more slowly. I believe the SPS10, for example normally rotated at about 20 rpm. Some ESM DF antennas are similar to what you describe, but of course they don't have to receive a return pulse so they don't have to rotate at the slower speed of the surface search radars. In fact, they need to rotate fast to be sure of picking up the incoming radar beam when it comes around. I don't think our surface search radars rotate faster than about 60 rpm, and that is on short range mode of five miles or so iirc.

Thanks for the clarification. Do you know the title of your book yet?

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Re: Tirpitz' Radar

Postby Dave Saxton » Sun May 15, 2011 5:01 pm

The maximal rotation speed of the Berlin antenna was 400 revolutions per minute or 6.5 revolutions per second. Which is quite a bit less than the similar Naxos detector receiver antenna design of 1300-2000 revolutions per minute. A rotating passive receiver antenna needs to rotate at high speeds in case the radar beam it may pickup is also rotating. The rotational speed of the Berlin antenna was variable and could be set at whatever speed best suited the circumstance. Of concern during the 1940s was the time span that the deflection's (pips) after glow persisted on the early PPI scopes.

The typical max detection range to fleet destroyers of Berlin S was about 30,000 meters, or about 33,000 yards. For small warships under 1,000 tons it could be 20,000 to 30,000 meters according to tests.

The typical detection range of the German centimetric equipment helps to explain why the Germans continued to plan for mounting large mattress antennas for the 80cm wavelength radar sets on destroyers latewar, even as centimetric equipment became available. 80cm Seetakt with the new high power transmitter modules could provide up to 40km detection range destroyers to destroyers. Detection range to aircraft could be as great as 200km for the high power 80cm sets.

We havn't settled on book title yet.
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: Tirpitz' Radar

Postby Bgile » Sun May 15, 2011 7:59 pm

I think most modern surface search radars and therefore their ppi displays rotate at a sweep every two seconds or so. I wonder why they go so much slower than the German one, which would have the advantage of painting the contacts more often. The antennas are much larger than the Berlin antenna, so maybe it's a question of wearing out the bearings.

Typical air search radars go much slower than that.

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Re: Tirpitz' Radar

Postby Dave Saxton » Sun May 15, 2011 10:26 pm

The image persists longer on the more modern display units compared to the earlier PPI display units, so they don't need so may rotations per a given time period to retain a good image on the scope.
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: Tirpitz' Radar

Postby Dresden » Sat Dec 08, 2012 8:37 am

So according to Seiche's article on Tirpitz's radar, the FuMO 27 had a 2x4 mattress, while the later FuMO 26 had a single 3x6 mattress? It also notes that she kept her FuMO 23s on the aft and forward rangefinders.

A pic for the Scharnhorst's radar calls out a 2x6 mattress for either a 26 or 27. So, could mattress sizes and radar sets be interchanged?

Why keep the 23s? Why not replace with 26s or 27s?

It also notes that a FuMB 7 dipole frame was used for a FuMB 4 detector, so can one assume these were compatible?

And why not use the 213 on all four AA directors?

Were any FuME/S/T sets ever mounted on KM warships for operational use?

Finally, would I be correct in assuming that in mid-1944 the best radar suite Tirp could have would be FuMO 26, FuMB 4, and FuMO 213?

PS: Dave S, did you ever publish your findings??

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Re: Tirpitz' Radar

Postby Dave Saxton » Sat Dec 08, 2012 5:17 pm

Dresden wrote:So according to Seiche's article on Tirpitz's radar, the FuMO 27 had a 2x4 mattress, while the later FuMO 26 had a single 3x6 mattress? It also notes that she kept her FuMO 23s on the aft and forward rangefinders.


Seiche's article is wrong on several points. What he describes as a FuMO27 is actually a Timor passive array.
Why keep the 23s? Why not replace with 26s or 27s?


Tirpitz was never equipped with FuMO23s. Production of FuMO23 ceased in April 1940. What is described as FuMO23s are indeed FuMO27s.
Why not replace with 26s


What we refer to now as FuMO26 did not exist until mid 1943.

It also notes that a FuMB 7 dipole frame was used for a FuMB 4 detector, so can one assume these were compatible?


Yes, any passive antenna could be used with any passive receiver. The Samos was used with the Timor because they were both direction finding capable.

And why not use the 213 on all four AA directors?


Good question. An answer may be because any firecontrol station could transmit data to any suitable firecontrol computor station on German warships. The FuMO26 sets could also be used to track and target aircraft.

Were any FuME/S/T sets ever mounted on KM warships for operational use?


Yes, they were used from the time of the channal dash in 1942 to the end of the war. They were certainly installed on TP

Finally, would I be correct in assuming that in mid-1944 the best radar suite Tirp could have would be FuMO 26, FuMB 4, and FuMO 213?


That would be incomplete. In addition, TP had in mid 44: FuMO81 Berlin, FuMO63 Hohentwiel K, and additional FuMO26 at the other two positions. Among the FuMB equipment there were Naxos ZM, Tunis, and additional Palau and re-located Sumatra antennas. Samos would have been replaced by Fano and Wanze.

PS: Dave S, did you ever publish your findings??

I'm still on track to publish my findings soon.
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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