World War II Japanese radar

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Siegfried
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Re: World War II Japanese radar

Post by Siegfried » Wed Nov 30, 2011 11:48 pm

The article Japanese Radar development prior to 1945 by "Shigeru Nakajima" has photographs of the M312 magnetron used in the type 22. These were water cooled magnetrons in glass tubes. There are also photographs of all metal magnetrons developed in 1941 (not fielded due to metals shortages) and an amazing 20cm 100kW continrious wave magnetron ment to be used as a 'death ray' weapon against aircraft.

Nakjima also mentions succesfull development of ten 10cm sets of a PPI radar by July 1945.

It seems the German Navy began introducing Hohetenweil radars around 1943 or 44. This amazing companies anode modulated 50cm radars produced 50kW pulses from a single tube that could be compared to UK Navy type 284. Yet this companies technology was underutilised in my view for many years. Thej produced a range of 50cm sets, including PPI sets that had more compact antena than Seetakt and were clearly suitable for search and maintiaining situational awareness and due to their small size were suitable for small ships including one PPI set that retracted into the sail of the type xxi u-boat.

Having said that: the FuMO 26/40G was fitted to the Italian destroyer Lanzaretto Malocello showing that even a small ship with a displacement of 1900 tons and a beam of 10.1 meters can carry the 6m antena of the FuMO 26, This thus gave these destroyers full blind fire capabillity.

The Germans seemed to regard crystal detectors of diodes as a solution to the noise problem.

Two german researchers Heinrich Welker and Herbert Mataré worked in duo diodes to solve this problem. Welker had already tried to develop field effect transistors before being assigned this task. Mataré had noticed puzzling distrubances in his galvometer when he tested his duo diodes. Later he realised this was a transisotr effect.

After the war the two were given jobs in France as part of Frances own opperation paperclip working for Westinhouse. There they invented the transitor (germanium point contact) the same time as Bell Labs did. In fact their "transitron" was more robust and entered production much earlier Mataré founded Intermetall in Düsseldorf, the world's first company, which offered diodes and transistors.

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Re: World War II Japanese radar

Post by Dave Saxton » Tue Dec 06, 2011 4:07 am

Thanks once again. This is all good information.
Siegfried wrote:......It seems the German Navy began introducing Hohetenweil radars around 1943 or 44. This amazing companies anode modulated 50cm radars produced 50kW pulses from a single tube that could be compared to UK Navy type 284. Yet this companies technology was underutilised in my view for many years. Thej produced a range of 50cm sets, including PPI sets that had more compact antena than Seetakt and were clearly suitable for search and maintiaining situational awareness and due to their small size were suitable for small ships including one PPI set that retracted into the sail of the type xxi u-boat.

..
Regarding Lorenz and their Hohentwiel radar. Lorenz was originally involved with GEMA in the development of Seetakt. GEMA invited Lorenz to participate because of Lorenz’s extensive experience as a military contractor. This gave Lorenz a leg up in their own radar R&D. Many of the secret patents filed by Lorenz were actually filed in behalf of GEMA and its scientists during those years.

However, once Seetakt was successfully developed the Kriegsmarine demanded that Lorenz be cut off from the KM radar projects. The German Navy saw Lorenz as a security risk because of their strong foreign associations with American corporate interests such as Bell Labs.

Lorenz then designed an aircraft tracking and flak direction radar for the Luftwaffe. It lost in competition to Wuerzburg. Lorenz persisted and designed the Hohentwiel air to surface vessel radar for the Luftwaffe completing trials in 1941.

Hohentwiel was one of the best ASV radars of WWII. Among its attributes were compact and simple design and high output power. From an airborne platform it could detect ships from 150km and detect the periscope of a submerged submarine from 6km. The airborne version used a simple form of lobe switching (pip matching) to allow blind torpedo attacks on shipping.

Hohentwiel had a power output of 50kw (30kw in airborne versions to prevent high voltage arcing at high altitude) and a 2 micro second pulse width, giving it target illumination energy of 100kw. The transmitting triodes were anode modulated with a high voltage pulse formed from a capacitor discharge being delivered to the anodes through a Balum Transformer. This limited the PRF to 50.

The KM realized by 1943 that Hohentwiel would make an excellent alternative to the U-boat mounted Seetakt derivatives (FuMO29 and FuMO30) because of its power output and overall compactness. FuMO61 (Hohentwiel U) demonstrated a 25% increase in range over comparable Seetakt models due to the greater power output. From late 43 production of FuMO30 was halted and shifted to FuMO61.

Although Hohentwiel wasn’t capable of the same precision or resolution as Seetakt it was capable of greater range than the 8kw output Seetakt models for typical ship to ship applications. Destroyers could be detected from 36km. As you point out, the accuracy and resolution were plenty good enough for general tactical use. Tirpitz was equipped with Hohentwiel K (FuMO63) in late 1943.

The application of PPI technology to Hohentwiel was the result of a renewed collaboration with GEMA. GEMA turned over the final development and production of the Drey Freya radars to Lorenz in 1942. Lorenz of course applied the PPI technology to its own Hohentwiel series of radars
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Re: World War II Japanese radar

Post by CmdrKeen » Wed Apr 04, 2012 11:31 pm

I just read this entire thread and found it most interesting and informative.
Thank you very much. The reason I'm posting in reply, is that I found a reference on page 60 of 'The Battleship Yamato' by Janusz Skulski, to a 'radar jammer';
"Radar jammer -- 7 antennas fitted on both sides and aft yard of air defence combat post, fore wall of tower, decks IX-X, and both sides of signal platform, deck V (1945)."
If this is what it sounds like (something to jam enemy radar) could this have prevented American shore, surface ship, or aircraft radar from detecting IJN Yamato accurately, or at least interfered with it somehow?
Or what does it refer to?

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Re: World War II Japanese radar

Post by tommy303 » Thu Apr 05, 2012 1:24 am

More likely the Japanese radar jammers were electronic counter measures which would blind the other guy's radar. It didn't prevent detection--obviously it left a signature of its own and let the enemy know you were there somewhere, but it could degrade the enemy's radar performance by transmitting noise or pulse bar patterns which would help screen what you were doing--which way you were going, how many ships were in your formations, maneuvers, etc. On a PPI display, the jamming would result in a washed out wedge. On a radar's A-Scope, it often showed up as false readings or background spikes which would obscure the target, although an expert operator might be able to pick some details out from the resulting mess. You would know something was out there, but not what it was, where exactly it was, nor what it was doing.

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Re: World War II Japanese radar

Post by CmdrKeen » Thu Apr 05, 2012 5:45 am

Really? I mean, all this endless talk about how, if an Iowa-class battleship ever met Yamato, it's all about how Missouri would target Yamato on radar from a distance and do radar targeting while in fast maneuvers and drop endless numbers of shells on Yamato, and how Yamato couldn't shoot back and hit anything.
Then I find reference to the radar jammer in the definitive Yamato book by Skulski, and you're telling me Yamato could block Missouri's radar so all they see is a blanked-out wedge on their circular radar scope.
This is really amazing news. Nobody else ever suggested this before.

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Re: World War II Japanese radar

Post by tommy303 » Thu Apr 05, 2012 4:12 pm

It would depend on how effective the late model FC radars were. If the Japanese jammers could not match frequencies, then it is possible that fire control radars could see through the jamming. Dave Saxton would be the one to ask in this regard.

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Re: World War II Japanese radar

Post by tommy303 » Thu Apr 05, 2012 10:52 pm

Again, Dave Saxton is the expert, but I believe if the Japanese ECM could mimic an Iowa's FC radar in frequency, it might be able to seriously degrade the fire control radar's effectiveness; similarly, might be able to blind the surface search radars as well, provided they could match frequencies. If it could not mimic or come close to the frequencies, it might have little effect.

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Re: World War II Japanese radar

Post by Dave Saxton » Fri Apr 06, 2012 2:05 am

Tommy is entirely correct in his comments assuming it really was a noise jammer (for what frequencies and how much power?). However, we would need to confirm that this was a jammer and not another radar device such as an antenna for a passive detector or for an active radar simply mis-labeled as a jammer. For example, Yamato's Mk1 Mod3 (Type 13) air warning radar had antenna lines running from the yard arms from the tripod mainmasts down to the aft AA command platform. Note the description:
7 antennas fitted on both sides and aft yard of air defence combat post, fore wall of tower, decks IX-X, and both sides of signal platform, deck V (1945
I can find no reference for successful Japanese ECM in the standard works such as L Brown. However, the USN Radar Operators Manual has several instructions about how to work through enemy jamming. Was this in response to actual enemy jamming encountered or "just in case"? It may have been included based on known German anti-radar activity.

The Germans were known to use various ECM and ECCM techniques from as early as 1942. The Germans used noise jamming against Allied metric radar during the Channel Dash, at Anzio, and used chaff (Window/Dueppel) against all Allied radar wave lengths.


I'm sure that ECM wasn't beyond the scope of the Japanese but we need to learn a lot more.
but it could degrade the enemy's radar performance by transmitting noise or pulse bar patterns which would help screen what you were doing--which way you were going, how many ships were in your formations, maneuvers, etc. On a PPI display, the jamming would result in a washed out wedge


Another advantage was to simply degrade the range performance of the enemy radar. Furthmore, in the Operators Manuals it instructs FC radar operators to not resort to max signal, but to keep lobe switching as they try and work their way through the enemy jamming. This is a further indication that the jamming may have been against the lobing frequency rather than opertional frequency. By turning off lobing, the bearing accuracy would suffer and this would result in no blind fire capability, and with Mk8 or Mk13 an inability to spot the fall of shot. This may be the primary intended result of lobing frequency jamming; one way or the other. The Germans knew about this technique and may have informed their ally.
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: World War II Japanese radar

Post by alecsandros » Fri Apr 06, 2012 11:06 am

If such a system was ever mounted on a Japanese capital ship, it was very late in the war, as the destruction of Fuso and Yamashiro in Oct 1944 showed the blindfire capabilities of US Battleship weapon systems were apparently un-obscured by any kind of countermeasure.

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Re: World War II Japanese radar

Post by tommy303 » Fri Apr 06, 2012 7:37 pm

This report from the US Technical Mission to Japan is interesting:

http://www.fischer-tropsch.org/primary_ ... 20E-07.pdf

It does not appear to treat Japanese radar and ECM in very high regards.

It is possible that the Yamato may have received some sort of jamming devices without the USN technical mission becoming aware of it in 1946--everything about the Yamato class was very much secret and the Japanese destroyed most materials which had anything to do with them at the end of the war.

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Re: World War II Japanese radar

Post by sonofsamphm1c » Sat Jun 02, 2012 11:28 pm

This is an interesting thread. After Iwo Jima speculation began that the tremendous costs were justified because the Japanese lost their Iwo Jima radar station. Is there anything in the records that indicates the Japanese were deriving significant military benefit from their radar on Iwo Jima?

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Re: World War II Japanese radar

Post by Dave Saxton » Wed Jun 06, 2012 3:08 pm

Adm. Spruance had always said that Iwo Jima was justified based upon this factor. Others have reported that it couldn't be the case because Japanese radar was so backward that the Japanese could not have been gaining much from it. However, during 1944 (when the planning was taking place) Spruance did not know of the true capability of Japanese radar, or be able to predict the capability of future Japanese radar against B-29 operations. They may have anticipated active German help for the Japanese.

Although the actual capability of the Japanese radar facilities on Iwo Jima itself was poor, its value within an overall system was not of little importance. The main factor is time. The earlier the initial warning (potenially provided by the Iwo Jima location) combined with other data provided by other facilities made it more likely that the Japanese could organize a more effective response, especially in terms of fighter aircraft. Since the B-29s were needing to go to low altitude tactics they could become vulnerable to more effectively organized night fighter defenses.
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: World War II Japanese radar

Post by lwd » Tue Jun 19, 2012 11:51 pm

tommy303 wrote:This report from the US Technical Mission to Japan is interesting:

http://www.fischer-tropsch.org/primary_ ... 20E-07.pdf
...
If I've done the math right the only IJN jammer was in the 140-160 MHz range wile the Mk8 FC system was around 3 GHz. Not likely to be a very effective firecontrol jammer.

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Re: World War II Japanese radar

Post by Engineman » Mon Mar 10, 2014 2:11 pm

Just been reading "run silent run deep" where the us sub uses radar to detect enemy ships. But wouldn't this give the subs position away?

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Re: World War II Japanese radar

Post by Steve Crandell » Mon Mar 10, 2014 4:35 pm

Engineman wrote:Just been reading "run silent run deep" where the us sub uses radar to detect enemy ships. But wouldn't this give the subs position away?
Today it would, but in the Pacific in WWII USN submarines used it all the time, to good effect. They often attacked on the surface with deck guns, also. It wasn't unusual to find Japanese merchants travelling alone.

I don't think the IJN used ESM equipment to good effect during WWII.

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