Gun precision / dispersion

[Thorsten Wahl]

From the schematic drawing it appears to me that only 50 % of dipoles were used for each direction measuring fine bearing.

Feinpeilung.png (188.85 KiB) Viewed 12825 times

[fsimon]

I think all dipoles were used, but the different receptions had to be integrated to get the sum, while the difference was used to find the center, i.e. the minimum.
I just learned, that while not loosing gain of the antenna when using Radattelpeilung, the noise level rises and integration of the sum diagram deteriorates accordingly thus reducing the range.
Best regards
Frank

[Thorsten Wahl]

if one splits one signal into several separate ones this costs signalstrenghts as the derived signals hast to be shielded against another.

[fsimon]

Would the same apply for lobe switching with additional loss through halving the antenna gain?

[fsimon]

FuMO 23 or FuMO 27 on Bismarck?
In 1941 the Seetakt radars were still designated via the older nomenclature, i.e. FuMG 39 or FuMG 40.
GEMA Birthplace of German radar history:
"In May 1940, after producing about 60 units, GEMA concluded their first
series of radars. Whereas shipborne units continued to work at 2000 Hz, groundbased
sets used, according to their purpose, either 2000 or 1000 Hz. The continually
increasing range, especially for air-warning equipment, brought with it
the necessity of reducing the pulse repetition rate to 500 Hz, corresponding to a
maximum of 300 km."

GEMA was beginning the production of the new 500 Hz radars in fall of 1940.

Herr Nilsson provided a list with the ships receiving FuMG 40 before Rheinübung. Bismarck is not on that list, but one device is unclear:
"Das sind die FuMG 40, deren geplanter Auslieferungstermin vor dem Beginn "Rheinübung" liegen.
32 ,,Z 15" vor dem 2.4.41 ausgeliefert
33 ,,Z 26" 8.4.41
34 ,,T 13" 6.3.41
35 ,,Z 5" 28.3.41
36 ,,Z 10" 12.3.41
37 ,,Lützow (Vormars)" 18.3.41
38 ,,Z 6" 5.3.41
39 ,,Calais VII" 27.4.41
40 ,,T 14" 11.4.41
41 ,,Z 27" 23.4.41
42 ,,Calais VIII" 1.5.41
43 ,,U-Boots-Versuchsanlage (NVK)" 2.4.41
44 ,,Calais IX" 17.4.41
45 ,,artill. Drehstand (Versuchsstand Nr.3 NVK)" 5.5.41
46 ,,Z 29" 9.5.41
47 ,,T 15" 13.5.41
48 Verbleib derzeit unklar 17.5.41 (ursprünglich für Scharnhorst (achtern) geplant, stattdessen wurde aber ab Juni 41 Nr. 2 von Gneisenau an Scharnhorst abgegeben. Gneisenau wurde neu ausgerüstet mit Nr. 80 u. 81) "

The GEMA history Birthplace of German radar states:
"The new series had a uniform pulse repetition frequency of 500 Hz, corresponding to a maximum range of 300 km. The multiplicity of types delivered until then was replaced by a standard group. The basic GEMA radar now consisted of power supply R with RH (high voltage) and RN (low voltage), RI (instrument panels), transmitter T with TU (Ultrateil, the self-exciting power oscillator), TS (modulator) and TN (power supply), frequency generator Z with ZP (receiver) and presentation unit N with NE (receiver) consisting of NA (RF unit), NZ (IF unit) and NB (main presentation unit with dualbeam CRTs), fine ranging and presentation unit O with OK (Messkette) and OB (fine range presentation unit with dual beam CRT), matching unit WA, transmission antenna V and receiver antenna W."

Trenckle states, that all Seetakt aboard ships starting with "Admiral Graf Spee"in 1938, "Gneisenau", "Scharnhorst", "Admiral Hipper", "Blücher" "Admiral Scheer" and "Deutschland" from November 1939 into 1940 worked at 500 Hz.
M.Dv.Nr. 950 Richtlinien Seetakt FuM Dienst of 1. August 1943 states that all Seetakt on ships invluding FuMG 39 worked at 500 Hz.

M DV 950 Seetakt.JPG

(245.87 KiB) Not downloaded yet

Geräteliste Na 320-339 from Juli 1944 clarifies the nomenclature from FuMG to FuMO:

Geräteliste KM Juli 1944.JPG

(186.36 KiB) Not downloaded yet

Dave Saxton has information about AVKS testing of Bismarck"s radars prior "Rheinübung" giving 500Hz and 14kW peak power.

My impression:
FuMG 39 were delivered at 2000 Hz but received 500 Hz transmitters from late 1940 while retaining the designation FuMG 39 due to retaining most of the initially delivered parts including the housing and mountings. TS 6 triodes were also delivered to FuMG 39 devices: Prinz Eugen for sure and Bismarck very likely at least for the foretop radar.
Any thoughts?

[Herr Nilsson]

My impression:
FuMG 39 were delivered at 2000 Hz but received 500 Hz transmitters from late 1940 while retaining the designation FuMG 39 due to retaining most of the initially delivered parts including the housing and mountings.

Definitely not!

[fsimon]

Thank you, Marc.
Can you give some more information to clarify?
Best tegards
Frank

[Herr Nilsson]

Gneisenau had two brand-new FuMG 40G in early Dezember 41(one TS6 and one TS1).
Gneisenau's old FuMG 39G TS1 was transfered to Scharnhorst and got a TS6 (Scharnhorst was the first ship, which had both devices equipped with TS6).
At the same time Tirpitz had one FuMG 39G with TS1, one FuMG 40G with TS6 and one FuMG 40G with TS1.
Prinz Eugen still had her FuMG 39G devices with TS1 and TS6.
All FuMG 39G retained 2000 Hz!

[fsimon]

Super,
Thank you Marc!

[fsimon]

Does anyone know, if the 10m step scaling (resolution) for the "Messkette" was only used with the 500Hz devices?
I understand that the 2000Hz devices could also be equipped with a "Messkette" with finer scale, but I cannot find the scale steps.
Best regards
Frank

[hans zurbriggen]

Hello Frank,
what I have found in H. von Kroge book for early 1940 (chapter 15, before introduction of TS6 and with 2000 Hz PRF) says:

Even though the higher accuracy of the Messkette had not found complete acceptance with the Navy and Luftwaffe, their ease of operation, and above all their resolution and accuracy, were being continually improved.
In practice the operator of the Messkette had to hold the echo pulse on the null mark of the CRT.
To this purpose the Messketten of the first design generation, GOK101 for Seetakt and GOK108 for Flum, were provided with fine adjustments, two scales and relay circuits. Four delay elements, A, B, C and D, were connected preceding the fine adjustment. One step of the A element corresponded to a distance of 10 m, of the B to 100 m, of the C to 1000 m, of the D to 10 000 m. The steps of A–C were switched, whereas D used relays.

I'm afraid this is a bit too technical for my knowledge (I hope you can understand better), but to my poor understanding this means finest step was 10m as well.

hans

[fsimon]

Thank you Hans,
that helps. I missed that passage or did not correlate it with the FuMG 39.
Thank you,
Grüsse aus Rostock
Frank

[Thorsten Wahl]

If i remember correctly, there was a detailed discussion on the Messkette in the Marinearchivforum some months ago.

...

Aufschlagmessgerät.jpg (22.97 KiB) Viewed 12670 times

The "Aufschlagmessgerät" appears from description as a switchable second zoomed A-scope .
That means it shows only a section of approximately 1000 m lenght around the measuring mark.

[Byron Angel]

Double post .....

[Byron Angel]

If i remember correctly, there was a detailed discussion on the Messkette in the Marinearchivforum some months ago.

...

Aufschlagmessgerät.jpg
The "Aufschlagmessgerät" appears from description as a switchable second zoomed A-scope .
That means it shows only a section of approximately 1000 m lenght around the measuring mark.

Hi Thorsten,
..... Are you describing what would be termed a “Range Gate” in USN radar terminology?

Byron