German Radar

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Thorsten Wahl
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Re: German Radar

Postby Thorsten Wahl » Sun Jun 21, 2015 5:25 pm

maximal measuring range 200km for Fumo 2 Seetakt (Calais) (but not ground to ground)

real performance of the Fumo on board Prinz Eugen 1944
Fumo Performance PG vs destroyer.jpg
Fumo Performance PG vs destroyer.jpg (34.73 KiB) Viewed 947 times

range is dependent on
installation altitude of the antenna
and height and reflective properties of target
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Re: German Radar

Postby Steve Crandell » Sun Jun 21, 2015 7:59 pm

I don't read German, but I'm gathering around 40km from Prinz Eugen to a destroyer. The same radar was used vs aircraft as against ships? In US usage air search radars are usually lower frequency, longer pulse width, and greater power. It doesn't provide the definition you need for navigation and target discrimination, but picks up aircraft a long ways out.

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Re: German Radar

Postby Thorsten Wahl » Sun Jun 21, 2015 8:27 pm

The aircraft was circling above a invisible object distance 38 - 40 km.

Destroyers came insight at distance greater then 30 km using FUMO from foretop
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: German Radar

Postby Dave Saxton » Sun Jun 21, 2015 9:05 pm

Steve Crandell wrote:I'm not intending to be "snarky" at all. I don't understand why you are taking offense. I'm trying to find out what kind of display the Germans used and how they turned their antenna, and what it looked like on the ship. I know what the US one looked like. It was called a "bedspring" for good reason, and you can see it on all manner of ships from destroyer on up. I'd like to know about German ships.
?


Okay Sorry for the misunderstanding on my part. In terms of how the antenna was turned and the display depended on the radar set.

On large warships the Seetakt set was mounted on the rangefinder. The electronics modules were mounted inside the rangefinder hood so that the antenna (often called a mattress) and the radar set could rotate together with the rangefinder through a full 360*. The rangefinder could be set to continuous rotation in one or both directions or it could be trained to aim at a selected position. On destroyers and light cruisers the set and antenna were mounted on a special mast called the zerstroyer saul. The center pod at the top of the mast contained the transmitter. Low voltage signals were conducted through a slip ring connection to the radar cabin for the other modules of the set. Later during the war the design was changed so that the transmitter was remotely located. Once again full rotation was allowed.

Seetakt/Freya had up to three indicators (not applicable to U-boat models). There was a coarse range indicator and a fine range indicator (combined using the same CRT in some cases) and also a fine bearing indicator. Once a target was detected on the coarse indication, the fine range system could be used to zoom in on and examine any portion of the time base. Pips from air targets as you know have a unique appearance on the scopes, and of course will have speed far exceeding that of surface targets. The target pip was placed on a null point in the middle of the fine range screen by cranking a hand wheel. This automatically measured the range electronically, which was displayed digitally to the nearest 10 meters. It also allowed the fall of shot to be seen relative to the target on the fine range indicator. Range rate and range was continuously up dated and measured by the operator holding the selected target on the center null line on the screen. These data were automatically relayed directly to the fire control computer(s)second by second by selsyn. The fine bearing display (module P or module PB ) could keep the antenna aimed directly at the selected target for bearing by centering the selected target pip at the center of the screen and holding it there. Accuracy was was 0.10*. On the PB module indicator there was global range display that highlighted the selected pip so that the was no confusion between target pips.This system utilized phased array scanning technologies. FuMO26 also could determine fine elevation to air targets using the phased array technology.

Hohentwiel (FuMO60 series) and FuMO31 Sophie radars utilized mast mounted mattress type antennas, as did FuMO25/33 Seetakt sets. These antenna mattresses were very compact (not FuMO25), only about 1.5 meters by 1.5 meters. Sometimes these antennas were combined with FuMB (passive radar detector) receiving dipoles on the same mattress. Hohentwiel could use PPI and/or a-scope type indication depending on exact model. Hohentwiel was not noted for it's precision, but was valued for its transmitter power. It was well suited to general detection service of both air and surface targets. Sophie was a 400 kilowatt Seetakt which used a unique zoomable linear display code named Paris II that there is no correlation to among US or British design. Sophie used conventional lobe switching instead of the phased array system.

The FuMO81 Berlin had antenna elements mounted inside a small radome and mounted on the head of a mast. It used only PPI indication. It was a surface search set not well suited to air warning because the beam width in the vertical plane was only 6*. There was a similar correlation to the American SG in this case, as SG was not good at detecting and tracking air targets. The same could be said of British Type 273, which is why they sought to replace both 273 and the 281/279 types with the single Type 277 system.

The other German radars using mattress antennas were suitable for tracking both surface and air targets because the beams were wide in the vertical plane.
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Re: German Radar

Postby Dave Saxton » Sun Jun 21, 2015 9:23 pm

Steve Crandell wrote: How far could Tirpitz detect Lancasters at 10,000 feet?


We know of one case were Tirpitz detected Lancasters from 140km out.
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: German Radar

Postby Dave Saxton » Sun Jun 21, 2015 9:27 pm

Thorsten Wahl wrote:The aircraft was circling above a invisible object distance 38 - 40 km.

Destroyers came insight at distance greater then 30 km using FUMO from foretop


That would have been a FuMO26 Seetakt on the foretop circa June 1944. Tracking destroyers from more than 30km is impressive for any WW2 radar.
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: German Radar

Postby Steve Crandell » Sun Jun 21, 2015 9:50 pm

Thanks for the info; that helped a lot!

The German proclivity for putting search radar on the main battery rangefinder cupola was, I think, a mistake. If you are shooting at someone it is difficult to keep track of the other contacts in the area.

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Re: German Radar

Postby Dave Saxton » Sun Jun 21, 2015 10:20 pm

Steve Crandell wrote:
The German proclivity for putting search radar on the main battery rangefinder cupola was, I think, a mistake. If you are shooting at someone it is difficult to keep track of the other contacts in the area.


I agree. And so did the German Navy after Barents Sea. The Hipper being surprised by Sheffield and Jamaica was caused by that very reason. They had two radars so they should have assigned the other set to keep up an all a round watch, while shooting using the first set, but they didn't. I think this is one reason why the KTB is a bit ambiguous there.

However, an interesting thing is that British made the same mistake as the Germans a few minutes later. In their case they had separate surface firecontrol, surface warning, and air warning radars, but they did not detect the Eckoldt until it was within a few kilometers from them because they had their search radars in addition to their fire control focused on the Hipper. Had the Eckoldt known they were enemy cruisers instead of German cruisers it could have easily sank both with torpedoes.

After Barents Sea we see the Germans planning to and beginning to install additional radar sets, mounted on masts, on their heavy warships. For example, on Prinz Eugen late war, in addition to the Seetakt sets on the foretop and aft rangefinders, we will find a FuMO25/33 on the main mast and a FuMO81 at the head of the foremast.
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: German Radar

Postby Steve Crandell » Mon Jun 22, 2015 1:13 am

OK, that makes sense. One of the US after action reports I read mentioned that it was a bad idea to assign a director that was directing guns at a target to look for a new contact. Hard to believe they actually did that ... it seems so obvious now, but ... there it was.

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Re: German Radar

Postby Dave Saxton » Mon Jun 22, 2015 1:23 pm

Steve Crandell wrote:OK, that makes sense. One of the US after action reports I read mentioned that it was a bad idea to assign a director that was directing guns at a target to look for a new contact. Hard to believe they actually did that ... it seems so obvious now, but ... there it was.


The Hipper's command was expecting their FuMB equipment to give them warning in such a scenario, and they had a false sense of security therefrom. Indeed on both German cruisers the Timor FuMB antenna was mounted opposite the foretop FuMO27 antenna on the foretop rangefinder.

There is an SKL document which analysis' the radar elements of this battle on the German side in detail. The Hipper's radar, the Luetzow's radar, IFF, and so forth. It states that Hipper's command reported that all enemy radar transmission intercepts with the FuMB equipment came from the South and none from the North. Why?

Burnett had taken the precaution of switching off his metric radars. The standard radar warning receivers such as the Metox and the Samos could detect transmissions down to a wavelength no lower than 60cm.
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: German Radar

Postby alecsandros » Tue Jun 23, 2015 7:51 am

Dave Saxton wrote:
Burnett had taken the precaution of switching off his metric radars. The standard radar warning receivers such as the Metox and the Samos could detect transmissions down to a wavelength no lower than 60cm.

Fascinating !
So Burnett approached with his radars turned off, in order to take Hipper by surprise. :clap:
But how did Sheffield's radars functioned so rapidly ? I remember radars of that period to require at least 30 minutes warm-up before functioning correctly ?

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Re: German Radar

Postby Steve Crandell » Tue Jun 23, 2015 9:47 am

When I was working on radars we had something called a "dummy load". When we wanted to stop transmitting we wouldn't actually switch it off, but instead switch the output from the antenna to the dummy load. Would Sheffield have that technology then? It wasn't very complicated.

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Re: German Radar

Postby Dave Saxton » Tue Jun 23, 2015 2:25 pm

alecsandros wrote:
Dave Saxton wrote:
Burnett had taken the precaution of switching off his metric radars. The standard radar warning receivers such as the Metox and the Samos could detect transmissions down to a wavelength no lower than 60cm.

Fascinating !
So Burnett approached with his radars turned off, in order to take Hipper by surprise. :clap:
But how did Sheffield's radars functioned so rapidly ? I remember radars of that period to require at least 30 minutes warm-up before functioning correctly ?


Not his 10cm and 50cm sets, but his metric wavelength sets were obviously not switched on. Such tactics by the British can be found in other cases. For example, British destroyers were often instructed to switch off all radars except 10cm Type 276 when operating in E-boat infested waters during 1943.

The Hipper was not equipped with detectors capable of picking up wave lengths below 60 cm, therefore it could not detect Burnett's 10 cm and 50 cm radars. The Germans did not know about the 10cm radars for another four weeks yet. The Luetzow, however, logged all its detections of enemy radar transmissions by impulse frequency (PRF) rather than by wave length.

Burnett had the 10cm Type 273 sets operating. Sheffield gained radar contact with what turned out to be the Hipper at 1105 hours with its Type 273. The detection range was 24,000 yards. It had to close to less than 13,000 yards before the radar contact could be visually identified though. Jamaica's Type 273 was knocked out by the shock of firing its first salvo.

Both British cruisers used their 50cm Type 284 gunnery sets when they opened fire at 11:30 hours. They had to use radar because their optics were iced up.

Why did Sheffield use its Type 273 in addition to Type 284 to range the Hipper during the shooting though? Was it because the Type 284 was not fully warmed up? Tovey, however, thought that it was because of Type 273's "excellent ranging panel" when he essentially chewed them out for this near fatal error in the use of their radars.

It is true that WWII radars using magnetrons or anode modulation required extended warm up times. This was not true of radars using grid modulation such as Seetakt. Seetakt only required about 30 seconds warm up time.

German Hohentwiel and British Type 284/85 used anode modulation. One manual for Hohentwiel warns that a minimum of 10 minutes was required for warm up. British manuals warn that Type 284 could take up to 45 minutes to warm up.

West Virginia's Foretop Mk 8 (magnetron powered) was unavailable when the Japanese were first contacted by SG at Surigao. It was still being tuned and settling in. It is noted in the report that the foretop Mk 8 could have been used by the time Wee Vee actually opened fire, but the aft Mk 8 which was further along the warm up and tuning process was used instead.
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: German Radar

Postby alecsandros » Wed Jun 24, 2015 6:22 am

Ah, thanks for clarifying,
So Sheffield fired using ranges obtained from type 273 and 284 radars. IMHO, her initial shooting was good, with repeated straddles and 3 consecutive hits in a 6-minutes interval.

Could one or more of the radars used on Sheffield be able to discern fall of shot (splashes) of 152mm shells at 11km range ?

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Re: German Radar

Postby Dave Saxton » Wed Jun 24, 2015 1:55 pm

alecsandros wrote:Ah, thanks for clarifying,
So Sheffield fired using ranges obtained from type 273 and 284 radars. IMHO, her initial shooting was good, with repeated straddles and 3 consecutive hits in a 6-minutes interval.

Could one or more of the radars used on Sheffield be able to discern fall of shot (splashes) of 152mm shells at 11km range ?


The British documents conflict on that point. Some read yes and some read no.

Type 284M had a pulse width of 1 microsecond. This means that its resolution for range was 150 meters since it was convention pulse radar, that did not use a non conventional method to measure the distance of targets. If the salvo was tight enough that it was contained within 150 meters then the splashes would not be registered. Type 284 used A-scope presentation (only shows range data) with the side to side aim of the antenna determined by if the trace flickered or if it held steady. Splash spotting for bearing would be difficult. During 1944 a spotting scope was installed in the transmitting room and some British warships, and a photograph was snapped at the moment the fall of shot was expected, to data log the event.

During the Battle of North Cape, Duke of York's 284M was unable to spot the fall of 14" shot and the Duke of York asked other British warships to report the fall of shot back by by wireless. The Germans intercepted these wireless messages and concluded in their follow up reports; that the British radar was not capable of directing pure blind fire. In ADM 281 one of the complaints about 284/85 was that it could not reliably spot the fall of shot. Also during the Battle of North Cape the Duke of York's 273Q was not used to spot the fall of shot in place of the 284, although its 273 was fitted with a PPI indicator.

Type 273 M through P used a longer microsecond pulse width than TYpe 284M. Type 273Q had two pulse widths, and two power levels. One pulse width was 1.5 micro second and the other was longer. The longer pulse width would be used for smaller targets and longer ranges even though the power level was lower. (The illumination energy is the pulse width multiplied by the pulse power.) The Type 273 sets on the British cruisers at the time of Barents Sea also used A-scope presentation. KGV had a prototype PPI installed to its 273 as early as mid 1942, but most 273 sets were not fitted with PPI indicators until 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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