Radar Question, No Not Smoke!

[regiamarina]

Hey Guys,

We were playing the other day and one of the new players, who had recently bought a German Fleet and has been reading up on them in the rules, had a question. Some German ships are listed as having radar but only the British and US ships are listed as having advanced radar in their Nationality options so only these two countries can fire through smoke or at night out to 40" correct? Not all radar fires through smoke? I assumed not and that only the ships listed as having advanced radar could fire through smoke, etc. but thought I should just double check.

This also got me thinking about my French fleet as some of them were refitted in the US and are given RDR fire control does this mean they are able to use the Advanced Radar nationality option as well?

[TheDreadnought]

Benefits listed under the Advanced Radar ability apply only to those nationalities with the Advanced Radar benefit.

Yes, French Ships refit in U.S. shipyards would have all the capabilities of U.S. radar.

[regiamarina]

Cheers mate, it seemed like the obvious answer but thought I'd double check.

Martin

[weseld1]

Very right. To explain, for those who care. At the start of WW2, the German navy was way ahead in radar development: They had produced four Seetakt radar sets in 1939 and with one prototype, this allowed them to fit radar to Scharnhorst, Gneisenau, Deutschland, Spee and Scheer, their five most powerful ships. Seetakt had been developed for use with the optical fire control system, but proved useful as a surface search radar as well. It was intended to provide very accurate range measurements (+/- 50 m at long ranges for the 11"" guns, where the optical system would be doing well to give ranges of +/- 200 m). The antenna was mounted on top of the 10 m base optical rangefinder, and would rotate with it. The optical rangefinder would provide the bearing to the intended target and the approximate range, while the Seetakt would provide the much more accurate range. Seetakt was never intended for completely blind radar-only firing. Even with the then very short wavelength of 80 cm, the 6 m wide antenna gave a beam width of about 6 degrees (100 mils) so the bearing accuracy was roughly +/- 50 mils - a zone 2000 m wide at 20000 m range.
Seetakt did not use the "plan position indicator" display we now see on the "Weather radar" where a sweeping trace paints a map of the land or sea around the station. Instead, the operators of 1939-1944 had an "A-scope" presentation, where a horizontal line across the screen would show little spikes at each distance from which an echo was received (bigger spikes for better echos). If two or more ships were all within the 6 degree beam, all would return radar echos and there would be a series of peaks, one for each range. In theory, one could have waved the antenna from side-to-side and determined the angle at which the peak for the target was the highest, but in practice, the rolling and pitching of ones own ship and target motion would make the spikes for each target (and echos from waves, clouds and islands) keep changing size, so the only way to tell which ship was at which range was to cross-reference it with the optical rangefinder. The optical rangefinder could tell you that the two closest ships were destroyers and the furthest one was the aircraft carrier.

At the start of the war, the British were far behind the Germans, having decided to start with a wavelength where they could transmit signals with really high power: 1300 cm! This gave them a lot of power, and could detect airplanes very far away, but to get a beam width as narrow as Seetakt they would need an antenna 100 m wide. Even on shore that would be impossible to rotate, so they looked for other ways to measure the bearing angles. The first radar used on Royal Navy warships was Type 79 with the first sea trials conducted in early 1939. It operated on a wave length of 7000 cm, had a beam width of 20 degrees, and was as useless for blind fire as Seetakt (it was really only useful for detecting aircraft). Pushing for still shorter wavelengths, they had reached the apparant limit of their existing tubes at 150 cm (still well behind the Germans 80 cm sets of 1939) by late 1941. Faced by the clear superiority of German radar, they looked for a way to get better bearing accuracy out of their inferior, long-wavelength radars, and developed lobe-switching. This technique allowed the US SCR-268 to get bearing accuracies of 1 degree, in spite of having a beam witdh of 12 degrees. Still not really adequate for blind firing, but six times as accurate as Seetakt.

The successful production of the cavity magnetron tube by the US and Great Britain allowed a whole new family of radars to be produced with the previously impossibly-short wavelength of 10cm starting in 1942. Their narrower beam widths, coupled with lobe-switching, gave bearing accuracies of 0.1 degree and made blind fire possible.

The German Navy was quite satisfied that Seetakt had achieved exactly what they set out to build, so they did little to improve its performace of Seetakt. They were more concerned with producing equally good radar models for installation in smaller ships and providing more than one set in each of their larger ships. They did push the technology to reach 50 cm wavelengths, and to make their later Seetakt sets more reliable, but did nothing to provide blind fire until it was too late to see action.

The Japanese, who had developed cavity magnetrons of their own, did not share them with the Germans and did not get the new radar sets into action in time to make a difference. Thus only the Americans and British (and a few ships they gave to their Allies) had a real blind-fire "advanced radar" capability.

[navigator37]

Regiamarina - Great question, I was about to ask it myself!
Weseld1 - Great technical recap
The best discussion of the topic I know of is Louis Brown's masterful "A Radar History of World War II" - still available (though expensive). At times dauntingly technical, this comprehensive work covers the radar development of all major combatants in every form - land, sea and air - and clearly shows it's impact as THE major war-winning technology in WWII.