Dear Arthur,

 

the latest increase of your  website, the  “Lehrunterlage Jagdschloss A”  for the German VHF Surveillance Radarsystem as well  as the Technical Manual 11-219  are both very interesting authentic papers for seriously interested fellows in radar history. 

 

Please let me introduce some remarks according the content of the papers:

 

A former Siemens & Halske representative held a couple of years ago an interesting lecture about the development of the German WWII “Jagdschloss” surveillance radar. He pointed out then, that the basic idea for the plan position representation of radar information (if the slant range and azimuth coordinates of the various targets in the field of view are represented) was borne 1936/37 at the Gema company, Berlin. However, the most restrictive reason for the realization of surveillance radars was the limited performance of the early radar transmitters and receivers.

In opposite to searchlight radars with the typical pencil beam the surveillance radar needs actually a beam that is fanned in the vertical direction, if aircraft are to be observed. So, for a similar power density at the illuminated coverage, the radiated energy must be higher than for the searchlight radar. However the power capability of the Freya transmitters couldn’t be increased without a time consuming new tube program.

Therefore occasionally the development of the “Jagdschloss” Surveillance Radar, Siemens & Halske tried to compensate the insufficient radar performance by an improved receiver. It was planned to use the new Telefunken LV 4 wideband double pentode for the rf preamplifier and the first mixer of the receiver. However, Telefunken had problems with the development of the LV 4 double pentode, so after all Siemens & Halske used the Philips EFF50 for the receiver front end of the “Jagdschloss” surveillance radar.  .

 The technical manual 11-219 seems to be derived from the original document:

 

OEMsr 411 - 95 , Survey of German Radar from the Countermeasures Point of View

 Originated by the Radio Research Laboratory of the Harvard University, September 4, 1944  

operating under Supervision of Office of Scientific Research and Development; National Defense Research Comnittee, Division 15 of Radio Coordination.

 It seems to be an updated version of the Document OEMsr 411 – 95 !

I havn’t found before any information that an alternative hard tube modulator (with the RS 323 tube) exist for the FuG 200 Hohentwiel airborne radar ?

 

My best wishes

  

Hans J

I would like to add: That already Chester W. Rice of GE in the US dealt with a PPI like system. And, would like to say: "PPI was alerady in the air:. He described a PPI like radar in 1936, be it without range measuring in the PPI display, as this was read-off a display panel (regard my contribution Radar II.)  

  

 

In September 2011 we have obtained from the UK the original Jagdschloss transmitter module

 

Jagdschloss transmitter codename Eibsee

Please consider our:  new dedicated transmitter webpage to this transmitter

 

Prinzipbild - Jagdschloss

Ln.- Ausbildungsstab 2

Zeichnung B/F 231 date 26.7.1944

Please click on this drawing as to open it in pdf

Please notice that you can print the full schematic at a single A4 sheet by using the option in "Acrobat Reader " print what you see at your screen" thus befor doing this adjust the size of the schematic at you computer screen!

 

List of Jagdschloss codenames (Tarnnamen)

 

•     Gemse  -   IFF receiver. Using 5 x RV12P2000, 1 x LD1 (local oscillator), 1 x RG12D2 (demodulator), 2 x LV1. Gemse was used in all other GAF radar systems as well.

•     Gh 8a  -   Amplifier for various controlling pulses. Having 2 x EF14 and 1 x RV12P2000. Two stages though with lacking valve data.   

•     HF-Weiche  -   The splitting filter, which had to separate the calling transmitter signal at 125 MHz from the FuG25a replying signals at 150 MHz.

•     Hochtastgerät  -   High power pulse-modulator having 1 x TS41 driver; and 3 x TS41 in parallel. This power stage generated the 25 kV anode feeding pulse for the transmitter Eibsee. Their anode current is being stepped up by means of the modulator transformer. This maybe a bit more complicate way of doing, but it is increasing system efficiency.  

•     Kreuzeck  -   The main Jagdschloss receiver. In contrast to regular practice based on Gema technology, Siemens & Halske redesigned many stages and improved also the normal receiver performance. Using now in the front-end 2 times push-pull stages using 2 x EFF50 (thus together 4 x EFF50). Between the two EFF50 push-pull stages the first oscillator signal is being injected (the second push-pull stage is acting as mixer stage; I guess creating a DSB signal). Employing 8 x LV1, a single LV3 used for the broadband video amplifier.    

•     O-Gerät   -   The main range display using an A-scope presentation. Also being linked with the returning IFF signal (Gemse). The OK unit is the time-base delay-line, by which means the time base is being delayed and the according distance is being read off a direct reading dial (I guess calibrated in 10 or 100 metre steps).

•     Nordimpulsegenerator  -   North marker stage, which is keeping the north marker pulse provided by a photocell attached in concert with the rotating Jagdschloss antenna, when it passes compass north. Using 3 x EF14 and 1 x LS50

•     Phot.Zell.Verstärker  -   The photo-cell signal amplifier which provided the north marker pulse, bring the top of the PPI screen in concert with the actual antenna position against 'Compass North'. Using 1 x REN901.

•     Riessersee   -  T/R stage. Also known as: Simultangerät. Using 2 x SD6 (SD6a). This type was later in the war apparently replaced by so-called Nullodes (Radar News 19)

•     Sternschreiber  -   The large screen PPI display. Having 6 x RV12P2000 and 4 x LS50

•     TSk IFF transmitter  -   Working with 500 Hz pulses having 2 x LS50 and in the PA 2 x TS41. Consequently, having in this case a much higher transmitting power as it is fed by 2.5 kV anode pulses.

•     Ü-Gerät   -  Known as Landbriefträger, including a three phase signal as to synchronise the rotating arc and the antenna rotation. Which also provided  signals via broadband telephone line covering the full radar signal including all PPI information towards a remote site. Like Flak bunkers or main air defence control. Please notice the according photo shown previously.

•     TSo  -  500 Hz pulse amplifier consisting of 2 x LS50

•     Z-Gerät   -  Time base generator, which provided several time base signals. All having 500 Hz, but with variable phase relation

When we consider the valve types engaged we can see that only LS50s - LV1s - TS41s - EF14s - SD6s and RV12P2000s are being employed (neglecting the single REN901 triode). The advantage is obvious, because service stocks could be kept very rationalised.