Gema Seetakt X-Gerät DXE 502 / 01
Front panel of the X-Gerät
Please click on this image and look how Günter Hütter's set looks like (better than this one, his set apparently came from U273). Both modules had been obtained via England. (courtesy Günter Hütter)
The two ceramic oscillator modules
According the hand written information operating between 359 MHz and 394 MHz
Oscillator stage to the receiver chain (1)
The staight silvered wire is to pick up the mixing signal (the mixer valve is on the far right) which is the product of the received (own) Seetakt transmitter signal. The ceramic stage is an oscillator stage. The actual receiver input is on this photo not visible (see next photo).
The test oscillator stage (2)
Please notice first the silvered straight wire which virtually runs towards us; this comes via an adjustable capacitive attenuator from the input signal connector. The upper straight wire connected onto the disc-trimmer down in the chassis, is to pick up some of this oscillator signal and injecting its content onto the receiving mixer stage. Where thus two signal will be available.
Please notice how the oscillator is to be tuned.
The tuning is commenced by means of more or less bringing inside the slit of a dielectric (ceramic) disc. This entirely contactless, as preventing from contact instabilities
The wire bridge is the connecting wire between the two signal chains (see schematics later)
How did it fit into the Seetakt system?
The principle set up of a Seetakt radar system (courtesy Günter Hütter)
The unit in the centre is the X-Gerät (courtesy Günter Hütter)
We can see that a small antenna receives first the transmitter signal. Represented by the upper oscillator stage (1) some photos previously. This signal finally will appear at the CRT vertically on the base line first. The base line (time base) is derived from the central time base control (Z-Gerät).
The lower oscillator module [see previously (2)] is triggered by the same time-base though is starting up this oscillator. This signal is send towards the upper receiver channel as well and is directly retransmitted towards the Seetakt radar receiver. This weaker signal is then received by the very sensitive main radar receiver module, known as N-Gerät. Before this is to be done, the following tuning procedure has to be accomplished:
The tuning of the upper stage by means of the tuning knob just next to X/g 726 until a signal appears at the controlling CRT (consequently, the X-Gerät is receiving the transmitter signal and thus tuned now at its frequency). Now the lower tuning setting has to be done until a second signal appears at the controlling CRT screen. The second signal tells us that both the Seetakt transmitter signal as well as the Seetakt receiver is tuned exactly at the same frequency, without the necessity of another target signal (the lower stage is acting is as a variable test generator; which has to be tuned until a second blip is appearing about the first tuned or set signal). You may ask why, simply when there is no target, whether because of misalignment or other reason, by means of this procedure one is assured that both transmitter as well as receiver is tuned (being adjusted) appropriately.
Tuning '130' and '131' is to adjust the proper signal levels between the X-Gerät and Seetakt antenna system
Please down load the (German) text and schematic of the according manual chapter (Beschreibung für FuM.G. (Seetakt) 41 G (gU) which is more or less equal to FuMO29 and/or FuMO30
Seetakt receiver module, known as N-Gerät
On the left the CRT display unit; on the right hand side the receiver front-end with combined IF stage.
Please notice that the protecting front cover has been removed. This more or less water resisting cover is for this occasion being removed.
Finally a photo of the Seetakt front-end with combined IF stages
Please notice that that they used here a similar oscillator module '110' like in (1) and (2)
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