Radar fire control

Guns, torpedoes, mines, bombs, missiles, ammunition, fire control, radars, and electronic warfare.
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Dave Saxton
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Joined: Sat Nov 27, 2004 9:02 pm
Location: Rocky Mountains USA

Re: Radar fire control

Post by Dave Saxton » Fri Nov 07, 2008 2:59 am

When it comes to British naval radar I can't reccomend Derek Howse's work Radar at Sea enough. Howse has proven invaluable when it came to placing in the proper context and understanding of many of these technical documents. Howse was somebody actually involved in the effort. Another person involved with the British effort was Bryan Callick. Callick was also a team leader of the Technical Mission to Europe investigating German magnetrons and other radar tubes. Callick's work is much more technical, but crucial to a more complete understanding nonetheless.

The Type 285M was the more advanced version of the 285, and the 282, 284, and 285 were based on the same basic 51.5cm wave length radar design. The main differences between the various 50cm versions were the antenna arrays best suited for the specific mission. The 284 usually used a 24' wide reflective antenna called the "pig trough", although it could also use an array of yagi antennas called the "fish bones" instead. The 285 usually used the fish bones type of antenna array. The 282 used a small pair of yagies.

The main improvements to the 50cm radars during the war were centered around a big increase in power and the introduction of lobe switching. The early (1941installations) versions had about 25kw of peak power. The M versions (new construction in 42, and upgrades to existing sets in 43) had about 125kw peak power. BTW, the British usually listed peak power, because it was easier to use in particular mathmatical formulas, instead of radiated power. This does not make an apples to apples comparison with radiated power. The increase in power made possible the use of lobe switching without a decrease in range, actually the battleship to battleship range of the 284 was increased from 24K to 29K. Another benifit was a decrease in pulse width.

Compared to the American 40cm radars the M versions of the British 50cm radars had better resolution, with a narrower beam width, and a range resolution of 150 meters (compared to 400 yards). The wide range resolution of the American Mk4 probably explains in part the trouble it had with low flying aircraft. On the other hand the Mk4 provided lobe switching on both the horizontal and vertical axis at the same time, which for some reason wasn't possible with the British 50cm radars.

The 285M had lobe switching on the horizontal axis, so that the bearing could be fixxed when directing guns vs surface targets, but the elevation vs air targets was by max signal, requiring optical assistance.
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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