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[Dave Franklin]

What are the effect for RFC of the R= capability?The Gunfire CRTs only address RFCs of R+, R-, and out.This seems of particular importance to the USN and KM, whose default night Gunfire CRT is based on R-.Should the default really be R=?

[Lonnie Gill]

The default used on the KM and US surface combat charts is "R -" fire control radar for Radar Fire Control (RFC). These represent the early war capacities. "R =" represents the earliest, largey experimental radars at the very start of the war. Few of these saw operational use. As listed on the Radar Availability Table (RAT) in the Bonus files elsewhere on this website, for the USN these were the Mark 1 or FA radars, only 10 of which seem to have been fitted to the Wichita (June 1941) followed by Brooklyn class cruisers. These were replaced early in 1942, before these ships saw action. Thus, for the USN, "R =" is only a historical footnote. The early war "R -" fire control radars used in the Guadacanal campaign and beyond were the Mk 3 or FC main battery radar and Mk 4 or FD secondary battery radar.For the Kriegsmarine, the earliest was the initial version of the "Seetakt" radar. This is correctly shown on the RAT as having first gone to sea in 1936 on the Graf Spee. Due to a typo, however, this is incorrectly shown in the R + column. "Seetakt" was a generic name; the early FuMG38G set on the Graf Spee only had a maximum detection range of about 8 NM and was not R +. The main early war sets used by KM ships were the FuMO 21, 22 and 23 series. Accuracies of the R = series early fire control radars were generally similar, but a bit less than the R - type radars. The major difference was in the power of the sets, which translates into range. Friedman's Naval Radar, for example lists the FA radar with a range of approx. 10,000 yds with range accuracy of 200 yds and 9 mils and a resolution of 400yds and 20 °. The "R -" FC radar had a range of approx. 20,00 yds with a range accuracy of 40 yds and 2 mils and a resolution of 400 yds and 10°. [These accuracy distinctions were less in practice than might at first seem, since there was a limit to the discrimination an operator could effectively make when displayed on the small CRTs being used.] Thus, in a game sense, the distinction between R = and R - fire control radars is range. R = RFC would be limited to 10,000 yds effective range, while R - RFC can use the full RFC range scale on the Kriegsmarine GUNFIRE CRT. My data is not that extensive on German radar, but there seems to have been several variations in the FuMO21 through 23 series as power increased and hence, range. From an actual use point of view, they seem to generally have performed about like the British Tp 284 and 285. Derek Howe's Radar at Sea is recommended for further reading on this. Hence, while the early version shipped on Graf Spee would clearly be "R =" (with limited range), I rated the KM fire control radars used in WW II as "R -." THe FuMO 22, for example is listed in Friedman's Naval Radar as having a detection range [larger than the useable fire control range] of 13 NMs on a large (battleship type) target with an accuracy of 5°. In summary, if you want to use Graf Spee's early Seetakt radar [R =], limit use of the RFC scale on the Kriegsmarine GUNFIRE CRT to 10,000 yds or less. The KM ships for 1940 + can use the full R - range scale as indicated on their Ship Logs.If someone has additional information on the German radars which would alter this, please advise, along with your references and we'll take another look. In the meantime, we need to clean up the Kriegsmarine part of the RAT.LONNIE