Rear Admiral Bey at N Cape

[Steve Crandell]

There is no "battleship profile" for any WWII radar. All radar contacts look like this: ^ or like this: * regardless of its a battleship, or a destroyer, or an iceberg.

This didn't seem right to me and I'm now reading "South Pacific Destroyer" about USS Maury, and the author states in several places when they pick up contacts on the SG radar with PPI they can definitely tell relative size between different classes of ship, and sometimes even the ship's approximate heading by the shape of the pip.

[alecsandros]

There is no "battleship profile" for any WWII radar. All radar contacts look like this: ^ or like this: * regardless of its a battleship, or a destroyer, or an iceberg.

This didn't seem right to me and I'm now reading "South Pacific Destroyer" about USS Maury, and the author states in several places when they pick up contacts on the SG radar with PPI they can definitely tell relative size between different classes of ship, and sometimes even the ship's approximate heading by the shape of the pip.

... Late war radars were more powerfull than the Fumo27 mounted on Scharnhorst in Dec 1943.

Nonetheless, the key indicator was range. No sane radar operator would expect to pick up destroyers at 40km. At 40km there could only be a large ship...

[Dave Saxton]

Heres some photos of USS Denver's SG indicator during the skirmish with two Japanese destroyers on March 6 43:

http://www.history.navy.mil/photos/imag ... i00386.jpg

http://www.history.navy.mil/photos/imag ... i00387.jpg

http://www.history.navy.mil/photos/imag ... i00388.jpg

The two big white bloches on the left and right are portions of the Islands Kolombangara and New Georgia. The large Island to the south is not regestering and the coast line of the Mila Strait is not showing. Denver is of course, masked by the large circle at the center. The one or two, sometimes three, white circles to the south are a USN DD and one or two US cruisers. US ships behind the Denver are masked by rain. The two or three white circles to the west of the US warships are the two IJN destroyers and a small island.

On the SG PPI the resolution for distance is 500 yards (300 on the A-scope), so all ship pips will be 500 yards deep regardless of their size. The resolution for bearing is 5*.

In the Mk-8 Technical Operators Manual it warns that all pips will appear as the same oblong shaped circles regardless or the size or orientation or range, and this could lead to the false impression that the pips are ships boadside on. The reason for all pips taking the same appearance, it further informs, is because the resolution for distance is 50 yards and the resolution for bearing is 2*.

[Dave Saxton]

... Late war radars were more powerfull than the Fumo27 mounted on Scharnhorst in Dec 1943.

Nonetheless, the key indicator was range. No sane radar operator would expect to pick up destroyers at 40km. At 40km there could only be a large ship...

That is exactly the advice given in the 1945 gunnery manual for BB59. However, this can not be depended upon. Small and large warships can be picked up at several different ranges depending upon conditions and detection range is highly dynamic. For example, even in 1941 the Prince of Wales' new Type 273 was able to pickup a light cruiser at a range of 52km, the result of abnormal propagation, but during the same period could pickup Renown at 30km.

Sheffield's Type 273P picked up both the Hipper and its escorting destroyers at 21 Km at Barents Sea. Type 286P could not pickup the German ships at range that day, and Type 271 on the destroyers could pickup the Hipper, to a max range of 8 miles, only after being put on the target by a visual spot.

BTW, Scharnhorst was no longer equipped with FuMO27 by Dec 1943.

[alecsandros]

That is exactly the advice given in the 1945 gunnery manual for BB59. However, this can not be depended upon. Small and large warships can be picked up at several different ranges depending upon conditions and detection range is highly dynamic. For example, even in 1941 the Prince of Wales' new Type 273 was able to pickup a light cruiser at a range of 52km, the result of abnormal propagation, but during the same period could pickup Renown at 30km.
.

... With all due respect Dave,
Those incidents were the exception, not the rule. Usualy, in most circumstances, each radar set could accurately detect an enemy ship category at a given range, or range interval...

At Surigao Strait, West Virginia started tracking Yamashiro and Fuso at 44.000 yards, Mogami at 30.000 yards and the destroyers at some 25.000 yards. They were using the Mk8 FC radar, which produced very good ranges and was probably the key equipment in the repeated straddling of the enemy ships...

[Dave Saxton]

Those incidents were the exception, not the rule.

Incidents like those happened a lot of times. Enough to make it not a dependable indicator of ship type. There would always be uncertainty. Uncertainty breeds paralysis of action. Just ask Captain Stange.

[Steve Crandell]

So Dave, you think Russell Crenshaw was lying? Why would he do that? He was the XO and CIC officer of USS Maury during many of her operations in 1943, including Vela Gulf, where they sank three IJN destroyers with torpedos. They didn't gain visual contact with them at all. Eventually they could see the fires and explosions from their hits. He spent many, many hours on that radar and you look at some photos of images from one cruiser and think what he says is not possible? In the book he talks about all kinds of potential interference, but also about very accurate navigation using that radar and very precise tracking of enemy contacts, determining accurate course and speed. I don't see how that would be possible looking at those images you linked to. I think those images represent a worst case, and possibly a radar that was incorrectly tuned and adjusted for gain. It also looks like the radar is set for it's maximum range, instead of putting the targets at 2/3rds max. From those images it looks like it was almost useless, and it wasn't. Far from it. It was an extremely useful combat tool.

I have personally stood many hours on a radar on a relatively old USN diesel submarine and it was much better than those photos, which by the way were taken in the dark with a WWII era camera. I really doubt that radar I stood watch on was much different from SG.

[Dave Saxton]

So Dave, you think Russell Crenshaw was lying? Why would he do that? He was the XO and CIC officer of USS Maury during many of her operations in 1943, including Vela Gulf, where they sank three IJN destroyers with torpedos. They didn't gain visual contact with them at all. Eventually they could see the fires and explosions from their hits. He spent many, many hours on that radar and you look at some photos of images from one cruiser and think what he says is not possible? In the book he talks about all kinds of potential interference, but also about very accurate navigation using that radar and very precise tracking of enemy contacts, determining accurate course and speed. I don't see how that would be possible looking at those images you linked to. I think those images represent a worst case, and possibly a radar that was incorrectly tuned and adjusted for gain. It also looks like the radar is set for it's maximum range, instead of putting the targets at 2/3rds max. From those images it looks like it was almost useless, and it wasn't. Far from it. It was an extremely useful combat tool.

I have personally stood many hours on a radar on a relatively old USN diesel submarine and it was much better than those photos, which by the way were taken in the dark with a WWII era camera. I really doubt that radar I stood watch on was much different from SG.

Those photos are typical of SG presentation. It is set to the smaller range scale, as the Japanese destroyers are less than 10,000 yards away. On a PPI, the resolution of the presentation can be no finer than the resolution cell of the radar. The instruction manuals make that clear. Thus the pips are about 500 yards in diameter on an SG PPI. SG and later era radar are apples and onions. Nobody is accusing anybody of lying. Perhaps the instruction manuals should have been read more carefully, though.

Nonetheless, relative target size could be judged better using the A-scope, and an A-scope was also provided. Crenshaw would surely utilize this feature. Signal strength is represented as amplitude on an A-scope, so if a target is examined on the A-scope more can be inferred even though it much more abstract. Sometimes a pip identity can be deduced to some degree by the motion and speed. For example, a barge or a merchant ship, or a small island, won't be going 35 knots. That would most likely be a destroyer. The USN analysis of the Denver's SG photos point out that a blurring of the pip indicates relative high speed motion. But there is always some -or a lot- of uncertainty about the identity of all radar contacts regardless.

I'm surpized that nobody picked up on the fact that the Hohentwiel operator on the German aircraft determined that one of the ships they tracked was most likely a battleship (actually was Duke of York) based solely on radar examination of signal strength relative to the other targets using an A-scope or a J-scope.

[alecsandros]

And very dubious is that the info was not received on the Scharnhorst, allthough Fraser knew he had been located by a German recon plane...

[Dave Saxton]

And very dubious is that the info was not received on the Scharnhorst, allthough Fraser knew he had been located by a German recon plane...

The Luftwaffe did not pass on the info to the navy until 1306. The navy did not pick up the aircraft's messages. The navy did not normally monitor Luftwaffe frequencies. It was broadcast on the joint Luftwaffe /Navy channel called FVLM only after the aircraft landed and the captain of the aircraft insisted it be passed on. The message passed on to the navy omitted the part that there was likely a battleship. It only read that there were several ships. The navy did not rebroadcast this message to make sure it was received on Scharnhorst. Scharnhorst did not have a B-dienst team embarked.

It was a failure of Intelligence that caused the loss of the Scharnhorst.