Tirpitz' Radar

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Dave Saxton
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Re: Tirpitz' Radar

Post by Dave Saxton » Mon Jan 19, 2015 7:53 pm

Christian VII. wrote:Just out of interest:

How good was German FC radar in terms of range & bearing accuracy in comparison to British & US FC radar in the following periods?:

1940-41
1942-43
1944-45
1940-41...........German...............British..........USN
Range accuracy:..40 meters...........240 yards.........N/A
Bearing Accuracy..0.10*................0.75*..............N/A

1942-43..........German................British..........USN
Range Accuracy:..40 meters............120 yards......0.1% of range + 40 yards
Bearing axxuracy..0.10*.................5-6 arc M (0.08*)...........3-4 mils (0.12-0.20*)

1944-45.........German ................British....................USN
Range accuracy:.25 meters.............120 or 40 yards..........0.1% of range + 15 yards.
Bearing Accuracy: 0.10*.................0.8*-0.10*................2-3 mils

NOTES:

The bearing accuracy is that of the radar itself but the directional accuracy of the mounting system of the antenna may be a little or a lot sloppier. Often times the director would need to be rocked back and forth to get a more accurate reading or an average reading.

The range accuracy of the British radars using the precision ranging panal was 25 yards. Howse lists 120 yards for Type 284M in practice, and British documents list 40 yards for Type 274 which began to be phased in on some major warships from May 1944. The differences of listed accuracy to that of the PRP is probably due to variance in the exact point in time the pulse fired. Type 274 used spark gap modulation (to produce 500kw) so the exact firing point in time was scattered. Type 284M used a thyratron pulser with a slight scatter in the timing of the firing of pulses.

Late war Seetakt with high powered transmitters (125kw or 400kw) could not use or not use the fine ranging system as well. This was because phase coherence could not be obtained or obtained consistently. The range accuracy was 100 meters on these late war high powered sets which used either a thyratron pulser or a spark gap modulator. The fine ranging system on the regular models could obtain 25 meters accuracy by 1944.

According to German document Taktischer Befehl Number 10, Euklid became operational on some German warships in March 1945. Euklid was now the primary FC radar system with Seetakt a back up system for FC on destroyers. Euklid had the same performance as Wuerzburg/Mannheim. The range accuracy would be 10-25 meters, and the bearing/elevation accuracy was within 0.10* 80% of the time and within 0.20* 60% of the time in that case. Wuerzburg/Mannheim/Euklid were conical scanning radars like SCR584, suitable for both surface FC and Flak FC. Euklid could be operated at 27cm or at 3cm.
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

Post by Christian VII. » Tue Jan 20, 2015 7:34 am

Wow, excellent info Dave! Many thanks!

German radar certainly was a lot better than what is written in some books, but they never go into detail and usually only list maximum range. Infact below is an example.

The book Naval Firepower: Battleship Guns and Gunnery in the Dreadnought Era by Norman Friedman claims that:
German FC radar was hopelessly behind British & US FC radar and was less useful at low elevations due to the longer wavelength (80 cm) used in comparison to the British Type 284 (50 cm) and US Mk.5 (40 cm).

Your data proves this to be utter hogwash however, but I'm rather stunned at how completely wrong Norman actually was on this.

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Re: Tirpitz' Radar

Post by Thorsten Wahl » Tue Jan 20, 2015 9:49 am

It should be noted that with regard of own assessments of the Kriegesmarine/Wehrmacht the Germans were convinced that allied radar equipment possess technological advantages at least in the beginning of 1944. Caution in judging seems appropriate to me.

Nevertheless I think the technical equipment and the use of radar in Germany of WW2 was more advanced then usually described in literature.

@Dave I could find references on the use of coastal Seetakts for detecting and locating of aerial mining operations. The seetakts were guided in by Freya air warning systems.
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Re: Tirpitz' Radar

Post by Christian VII. » Tue Jan 20, 2015 11:26 am

Some publications dismiss German radar as primitive and altogether useless in comparison to Allied radar however, which is rather disturbing considering the truth is directly opposite = The Germans actually started out with better radar, and during the war developed & introduced radar equipment just as good and better than the Allied ones in some respects.

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Re: Tirpitz' Radar

Post by Christian VII. » Tue Jan 20, 2015 12:31 pm

Almost forgot to ask Dave, what was the range of the radar FC onboard the BBs of the major nations in the periods mentioned before (40-41, 42-43 & 44-45?)

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Re: Tirpitz' Radar

Post by Thorsten Wahl » Tue Jan 20, 2015 1:08 pm

At the beginning of 1942 british and german surface radars had defintively range to the visual horizon for ground targets

so
mounted on ships range was depending of installation altitude and the hight of the target(and its reflective properties)
small ships wer usually lower in height and had smaller reflecion

but small ships with radarreflectors will produce a radarreflection similar to a big ship
Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!

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Re: Tirpitz' Radar

Post by Christian VII. » Tue Jan 20, 2015 2:56 pm

Thanks Thorsten, but was the detection range the same versus various types of vessels? Like for example in 43 were German & British FC radar equally capable at picking out and accurately directing fire on the same size targets?

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Re: Tirpitz' Radar

Post by Dave Saxton » Tue Jan 20, 2015 3:01 pm

Christian VII. wrote:Almost forgot to ask Dave, what was the range of the radar FC onboard the BBs of the major nations in the periods mentioned before (40-41, 42-43 & 44-45?)


The range of the early model Type 284 was tested on KGV. It could detect:

Destroyers to 14,000 yards
Cruisers to 20,000 yards.
Suffolk's 284 tracked Bismarck to 26,000 yards max

From 1942 Type 284M had a BB to BB range of 29,000 yards.

The USN operators manual lists the 40cm radars as having a BB to BB range of:
27000 to 28000 yards or 25km.
Range to destroyers is listed as 16,000 yards.

In trials using Graf Spee in 1938 established early model Seetakt to be effective to:
25km panzerschiff to panzerschiff.
To small craft it was about 10km.

In 1940 the first series of Seetakt were superseded by the 1940 versions with 4x more power. This increased the BB to BB range to:
30km.
In 1944 the large antennas such as FuMO26 increased the range a further 30%.

In May 1944 tests were conducted using a Calias B Seetakt with the 125kw and 400kw transmitter modules along with a new fine ranging system. It tracked steamers and warships in the North Sea to:
+40km
Aircraft to 200km.
von Kroge lists BB to BB range as +50km

USN Mk8 came into service during 1943. Its BB to BB range was:
42,000 yards

British Type 274 came into service in May 1944 with 500kw of power. Interestingly, some RN literature list the range to a BB as only 34,000 yards in tests. What might be going on here, was that the beam was so narrow it only got part of a large ship in the beam so the radar cross section was that of a smaller ship. Another interesting fact was that Type 274 could not spot the fall shot. Its beam was so narrow that most or all of the shot would fall out side of the beam. The transmitted beam was not scanned to hide the scanning frequency from enemy jamming. In 1947 a splash spotting radar was piggy backed onto the Type 274 on the Vanguard.
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

Post by Dave Saxton » Tue Jan 20, 2015 3:29 pm

Christian VII. wrote:The book Naval Firepower: Battleship Guns and Gunnery in the Dreadnought Era by Norman Friedman claims that:
German FC radar was hopelessly behind British & US FC radar and was less useful at low elevations due to the longer wavelength (80 cm) used in comparison to the British Type 284 (50 cm) and US Mk.5 (40 cm).
.
What I think Mr Friedman is assuming is greater sea clutter as a result of the longer wave length. Sea Clutter does increase with longer wave length once the waves reach a height that they act as reflecting dipoles to the wave length of the radar. But this is usually a problem with wave lengths measured in meters and is a lesser problem at decimetric wave lengths. Sea clutter is a greater problem with centimeric wave lengths than decimetric wave lengths because the reflectivity to water becomes greater at centimetric wave lengths. That is why sea clutter filters were developed for some S band (9cm) and most X band (3cm) radars during the 50s and 60s.

Many secondary sources claim that Seetakt would have a severe sea clutter problem because it mostly used vertical polarization instead of horizontal polarization. In tests of early British airborne radar it was found that sea clutter was unbearable with vertical polarization and so horizontal polarization was adopted. USN tests conducted during the 80s found that sea clutter problems depends mainly on the grazing angle. Below a grazing angle of 5*, or low over the sea, vertical polarization yields slightly less sea clutter than horizontal polarization. Above 5* through almost 90* grazing angle, the sea clutter is significantly less with horizontal polarization. Right at 90*, sea clutter is less with vertical polarization. So the Germans (and the British in the case of airborne radar) were correct from the beginning. Some Seetakt sets did use horizontal polarization.
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

Post by Dave Saxton » Tue Jan 20, 2015 3:46 pm

Thorsten Wahl wrote:but small ships with radarreflectors will produce a radarreflection similar to a big ship
This potential problem was noted during tests of FuMO71 (Lichtenstein) on S-boats. A large parabolic reflector antenna was tried to improve range perfomance, but the larger antenna actually reflected enemy radar waves giving the S-boat the radar cross section of a large warship. That was the end of that experiment.
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

Post by Thorsten Wahl » Tue Jan 20, 2015 4:12 pm

@ Christian VII. do you came from the world of warships forum?
Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!

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Re: Tirpitz' Radar

Post by Christian VII. » Tue Jan 20, 2015 5:07 pm

@Dave

That's pretty surprising to me, I was sort of aware that the Germans possessed radar with the same range & capability, but I didn't know that they made radar sets late in the war that actually outperformed the late war allied sets so comprehensively. Did the Allies confirm this performance after the war? And is it well documented?

Not that this particularly surprises me, as there was a lot of allied aversion toward German equipment and achievements both during the war and emmediately postwar. Another good example, although in a completely different area, is the complete dismissal of the StG44 as a usable smallarm by the British army, whilst today it is pretty much heralded as the best smallarm of the war.

@Thorsten

No, why? I was thinking about joining it (there are apparently two) as I actually learned about this forum from reading a thread over there ☺

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Re: Tirpitz' Radar

Post by Thorsten Wahl » Tue Jan 20, 2015 7:33 pm

Ther is a guy quoting Dave and you are wandering around in the gaps left. but no problem come to the "experts" :whistle:
Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!

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Re: Tirpitz' Radar

Post by Christian VII. » Tue Jan 20, 2015 9:06 pm

Thorsten Wahl wrote:Ther is a guy quoting Dave and you are wandering around in the gaps left. but no problem come to the "experts" :whistle:
Are you talking about this thread?: http://forum.worldofwarships.eu/index.p ... -and-wwii/

If so I was actually reading it all this time, and it is indeed one of the reasons for my questions :D

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Re: Tirpitz' Radar

Post by Dave Saxton » Tue Jan 20, 2015 9:18 pm

Christian VII. wrote:@Dave

That's pretty surprising to me, I was sort of aware that the Germans possessed radar with the same range & capability, but I didn't know that they made radar sets late in the war that actually outperformed the late war allied sets so comprehensively. Did the Allies confirm this performance after the war? And is it well documented?


When I first started looking into this topic I accepted as a matter of fact the common wisdom. It was only as evidence began to trickle in over time that I began to see that the storey was very much incomplete. Much of the problem was that German radar was cloaked in such secrecy by the Germans themselves that they didn't know much about either. This included naval officers. Even talking about it, could and did land people into concentration camps during the war. In keeping with this culture of Nazi Germany the Germans themselves destroyed much of the documentation at the end of the war. Other documentation was destroyed during the bombings as well. In the forward written by Louis Brown of von Kroge's history of GEMA Brown wrote:
The story of radar's invention and development in the years proceeding and during WWII is a confused one, with serious gaps in a record confounded by error and tinged in mythology. This unfortunate state of affairs is the direct result of the severe secrecy that was imposed on this strange new vocation. For many years the people writing the history of radar had been participants in its formation and maturation, a circumstance that gave weight to their presentations but that invarably skewed their articles and books toward narrow points of view. Given that the descriptions of the Allied efforts are covered in a highley irregular way, it is hardly surprising that those of the Germans and Japanese are but poorly covered, and are certainly not well known to English language scholors....
An example of why it is often stated that German radar was not capable of blind fire is that it is known that the KM asked in 1938 that lobe switching (required for blind fire) not be included in the equipment. This is absolutely correct. The assumption is that this included all Seetakt models for the remainder of the war or until after it was too late to have any effect on the course of the war. Even Brown made these faulty assumptions. Not well known is that in 1940 the new models incorporated a better type of advanced lobe switching and that this improved technology was indeed used aboard KM warships. The apparent radar failures at Barents Sea and at N Cape made it it easy to assume that the radars were not capable of directing blind fire. In fact it did direct blind fire successfully in these battles, but the failures in these battles are the result of much more complex circumstances and other complex issues not well known at all.
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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