German Radar

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Steve Crandell
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Re: German Radar

Postby Steve Crandell » Wed Jun 24, 2015 3:53 pm

There is a table of radar gunnery ranges for the USN Mark 3 radar in one of Bill Jurens' articles, and it shows 10,000 yards for detection of 6" splashes from an antenna 125 feet above the water plus a pre amplifier.

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Dave Saxton
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Re: German Radar

Postby Dave Saxton » Wed Jun 24, 2015 5:45 pm

Steve Crandell wrote:There is a table of radar gunnery ranges for the USN Mark 3 radar in one of Bill Jurens' articles, and it shows 10,000 yards for detection of 6" splashes from an antenna 125 feet above the water plus a pre amplifier.


The British 284M might be similar assuming it has a similar signal to noise ratio.
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.

nebfer
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Re: German Radar

Postby nebfer » Wed Jul 22, 2015 4:50 am

Dave Saxton wrote:.

Been reading up on German Radars, and Im getting that your of the opinion that Germanys radars in WW2 where Generally not as bad as often stated?

It's often stated that German WW2 radars where out right inferior than their allied counter parts, and a large part of that is due to their failure to develop the cavity magnetron until rather late in the war.

However your saying that this is not necessarily the case, Not that they where better than their allied counter parts but at the lest where not that far behind?

So how exactly where German Radars inferior to their allied "counter parts" in the later part of the war?

Is it say along the lines of compactness? the allies could make more compact systems? due to the use of the cavity magnetron? What advantages dose the "CM" have in radar usage in this time frame?

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Dave Saxton
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Re: German Radar

Postby Dave Saxton » Thu Jul 23, 2015 3:19 pm

nebfer wrote:Been reading up on German Radars, and Im getting that your of the opinion that Germanys radars in WW2 where Generally not as bad as often stated?

It's often stated that German WW2 radars where out right inferior than their allied counter parts, and a large part of that is due to their failure to develop the cavity magnetron until rather late in the war.

However your saying that this is not necessarily the case, Not that they where better than their allied counter parts but at the lest where not that far behind?

So how exactly where German Radars inferior to their allied "counter parts" in the later part of the war?

Is it say along the lines of compactness? the allies could make more compact systems? due to the use of the cavity magnetron? What advantages dose the "CM" have in radar usage in this time frame?


When I first started to research this topic I expected to find the conventional wisdom confirmed regarding the inferiority of German radar vis Allied radar. But that was not what the data indicated. In terms of performance, German radar equipment was more or less the equal to Allied radar at any given time, and clearly superior early war.

Of greater significance is how the radar was used. The German Navy dropped the ball in terms of officer training of how to better use this new technology.

There is nothing special about the cavity magnetron in and of itself. Indeed the Japanese developed the cavity magnetron independently by the early 1940s but this did not translate into superior radar equipment. In fact the performance of Japanese Type 22 radar equipment was clearly inferior to that of both Allied and German radar equipment, particularly in terms of resolution, despite their cavity magnetron, and the use of centimetric wavelength.

The main advantage of the (strapped) cavity magnetron was the ability of it to produce centimetric or microwave radiation with power outputs of tens of kilowatts. The Japanese cavity magnetrons were not strapped and early European magnetrons were also not strapped. They produced outputs of less than about 5 kilowatts. Centimetric wave lengths create much higher antenna gain without needing to use large antennas. Antenna gain is essentially how focused and concentrated the beam is. Higher antenna gain provides two main advantages. First higher gain can (but not always) result in an automatic increase in range attainment. Secondly, it can produce a narrow beam while using a relatively small antenna. The result of a narrow beam is superior bearing resolution (not resolution for distance as that is a function of time parameters not frequency).

Longer wavelengths can also utilize a narrow beam through the use of larger antennas. However, to obtain a narrow beam with metric and decimetric wavelengths can require such a huge antenna that it can become impractical for use aboard ships. This was why Freya, at 240 cm wavelength, was not used aboard ships. Seetakt still required a rather large phased array mattress antenna, at 60-80 cm wavelength, which was made even larger by 1944. The use of extra large antennas, post 1943, operating in common mode, allowed Seetakt to keep pace with late war performance demands, nonetheless.

Seetakt was originally designed with a cavity magnetron operating on 52 cm. The magnetron was designed by Dr. Hans Holmann (secret patent issued for in 1938), and mounted directly to the antenna. However, it was dropped in favor of a twin triode transmitter in early 1936. The reason it was dropped was because of the inherent instabilities of magnetrons, such as pushing and/or pulling the frequency, and the scattered and somewhat random timing of pulses (strapping helps ameliorate these problems but does not eliminate them). Seetakt used a central impulse geraete which was regulated by a master modulation. The pulses were thus precisely regulated and coordinated according to timing, and also phase. This was necessary for the proper function of the fine ranging system, which provided a excellent resolution for range using a 2 microsecond pulse width.

It is true that cavity magnetrons can result in more compact systems, using small enough antennas to be mounted at the head of a mast. The Germans applied the strapped cavity magnetron to their Berlin PPI surface search radar systems introduced by mid 1944. Berlin utilized a small radome mounted on the head of mast. Such design was not practical using Seetakt.

The primary role of Seetakt by 1944, now using extra large phased array antennas, was changed to that of firecontrol. Seetakt had the necessary accuracy (since 1940), and by 1944, with common mode antennas, and in some cases high output power, more than ample range attainment for that role.
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.

Steve Crandell
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Re: German Radar

Postby Steve Crandell » Wed Jul 29, 2015 10:05 pm

A good example of poor understanding of radar in the USN was the first naval battle of Guadalcanal. Halsey had just been chosen to command the SE Pacific forces and he put Calahan in charge of the US force over Norman Scott. The latter had an excellent command of radar and night fighting from his previous experience in night battles and had been training his force. Calahan chose San Francisco as his flagship because of her good flag spaces, but she didn't have the latest radar. He should have chosen Portland or Helena. In any case, he didn't understand night fighting and made a real mess of it. He was made a hero because he was killed on the bridge of his flagship.


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