About the Stuttgart FuG 03 / III* receiver module

* At section 2d we found readable at a label that a module was designated: Fu G 03 / E III. We may thus deduce that we have to deal with version III.


On the day our Nachtfee apparatus arrived from the US, on 11th November 2011, Antoon Steenbakkers  told me that he was promised a German receiver module by an US HAM. He showed my a photo to which I instantly responded this is a Stuttgart system related module.

The guy is OM Brian Harrison, KN4R

It took nevertheless more than 3½ years of expectation.


Last Saturday 6 June 2015 this set was collected


Page initiated: 8 June 2015

Status: 12 June 2015



We, finally, got the receiver on a long-term loan base

Our aim is to put it on display combined with the Telefunken pendant DMG 5K (system code-name Michael) receiver module.


In those days, both, Telefunken and Lorenz, were German leading electronic companies; albeit, following different lines and ways of development and applications.

For what ever reasons, the Stuttgart UHF repeater system was less used than the Telefunken systems - like: Michael and Rudolf (DMG 5K,   DMG 3 and DMG 3aG).

A reason might have been, that the Lorenz apparatus FuG 03 operated at the limit of the, valve controlled, frequency spectrum of > 1000 MHz (>1 GHz).

Sadly, someone in the US did not dare this apparatus technique, as it must have been kept for many decades in a kind of kennel; wind and heavy humid did leave many deteriorating traces. Unbelievable the many different hairs and other means found within it. Neglecting oxide caused by being within water for multi times. Which means countering the most obvious signs of deterioration is not determined, yet.

Is it worth showing such a set in quite poor condition?

Yes, it does!

Because, the set is so rare.

What might not be possible, as we do in many occasions, is bringing it in an operational state again.

The fundamental problem we encounter first, is getting documentation of the FuG 03 system.

Some photos are apparently around.

Here we face the basic problem of the internet.

Most of you do believe - that everything can be found on the web. This proves not to be true, when something is rare.

Also - it is not everyone's cup of tea cooperating with others - than being satisfied that he or it possesses something that someone else is desperately looking for; for some this seemingly is a drive of their life.

I truly believe, that our website is a very good example of sharing knowledge widely. Mentioning occasionally some details - is completely different - from providing full access to knowledge.

We do not provide documentation that isn't fully accessible, thus all is without restrictions reproducable. Only, sometimes, the copyright holder forces us to accept limits of free usage. In these cases, we weighted pro and cons, often accepting the limitation though, where giving access to worthwhile knowledge prevails. Though, counting these rare occasions you don't need a full hand!

Therefore, I repeat our call for Stuttgart FuG 03 technical documentation. When it has to be purchased for a realistic price, we are in. 


Left us start first with viewing the Stuttgart FuG 03 receiver module



The type label is not well readable

It is apparent, that someone did label it with English language explanations



Fu G 03/ E ?? (due to recent finding we know now that it should be read / E III)

12136 / dmr / 41

This is the only readable type number label found at the back-side of the receiver section

What can we learn from it?

Fu G 03 - apparently is the type number of this Stuttgart apparatus system, where 'E' might have stood for Empfänger, in English - receiver

12136   might point at serial number 136

dmr was the GAF code-name for Lorenz

/ 41 does mean, according German wartime practice, 1941

 To what we know, not yet 200 full systems had been purchased by German military services.



Viewing the left-hand side of the module, especially the RX front-end

Later investigations proved that behind this plate we find the mixer stage with mixer-diode: RD2,4Gc



Looking at the right-hand side of the Fu G 03 receiver module

When you look carefully at the right-hand connector (look through the slit), it is clear that only some of the top-contacts being used; hence, most likely the power inlet.



Viewing the power supply section

I guess, without possessing a schematic, but relying upon decades long experience, that on the left-hand side a STV 280/80 being applied and left of it a EW ?? (baretter); for stabilising the current supplied onto the STV stabiliser tube (multi voltages).

Viewing this photo carefully, it appears to me, that the power-supply module can be pulled out its frame. Which should later be done.



Viewing the receiver front-end



RD12Ta1 in a special fashion, serial or batch number 577/7

The RD12Ta1 and/or RD12Ta is a typical Lorenz product. These types were known as: Napf-Röhren.

Construction based upon patent DE890848 applied for successfully on 17 May 1939, by Löb.

It was used extensively by R&S within their VHF and UHF receivers  known as Samos and Fanö

However, in this application it was stretched up to its limits being about 1000 MHz.



Viewing the valve base



Viewing what is inside the valve mounting (socket)

My main concern is, where did they mount the mixer diode, because a valve (like a RG12Ga) can nowhere be found, yet?



The IF module being pulled-out slightly

The valves being mounted underneath the rectangular plates.



Looking at socket base V 4. Quite curious, as it was no custom mentioning at the top of a valve socket the valve number. I guess, this was done for practical reason, because there does not exist another way; as the rest of the circuitry is kept invisible. Likely not for security reasons, but for screening off environment



Viewing the IF module from behind (just what faces the front-panel). What I never expected, is the appearance of modular connectors - as these were widely applied by Telefunken in their Köln E 52 and Ulm E 53 receiver concept

These smart connector types were after the war widely used in Russian communication gear.

Please, notice also the dirt found between the module frame and the two standing capacitors.



Viewing this modular connector more in detail

It is evident, that it can be build in any length. 



The poor state of storage is apparent


A question is becoming acute, what should we do with the un-reversible oxide at parts the front panel frame?  

Keeping it as it currently is, or removing the oxide with care?

I believe, that some action is due to be undertaken.

From our long year practice, we know that Kontakt 88 (lubrication) oil is capable of dissolving the oxide from the non-oxide parts. The problem arises, when oxide penetrated deep into a metal subject, like is the case in this Al - Zn frame; or is it a mixture of Mg? The latter responding volatile upon humid, particularly when protection vanishes.

After removing some Al oxide I decided to leave it this way, for the time being. 



On 12 June 2015

We continue first with additional photos taken from the quite desolate, though, interesting Stuttgart Fu G 03/ III

Let us first continue with viewing some demounted modules

It has to be noticed first, that Werner Thote suggested correctly that the various parts can be 'refreshed' by using air pressure. This has been accomplished in the meantime, though, these photos had been taken before doing this. 



Viewing the space  where the power supply module has been pulled out 



Looking towards the front panel wiring 



Having removed the module left of the receiver front-end section



Viewing it in a different way



Cover being removed, looking at the relay section



Viewing what is underneath



Viewing towards the wiring of the front-panel

Please bear in mind, that after this photo session, we removed most of the dust by means of using air pressure.



With some patience, and some deal of luck, I removed a cover plate, having no idea what to expect. The tube-connection left of the mixer diode RD2,4Gc leads towards the IF stage

Found is the hidden mixer device 



Viewing this section differently



The mixer valve RD2,4Gc

I would have expected type RD12Ga

It has to be noticed though, that the RD2,4Gc was used also in the Korfu E351


Time has now come to focus our attention towards the Michael receiver module to the DME 5 K system. The symbol E might have stood for Empfänger, as this was also the case with the above shown Stuttgart Fu G 03 / E III 



Stamped type label to DM E 5 K   

Ln 20302

Hersteller bou (Telefunken)



Front panel of the Michael receiver module (E-Einschub)



Access door to the receiver tuning section



Viewing the tuning compartment in detail

'Mo 1' is the tuning motor which being controlled by the AFC circuitry

No one can say that it isn't a neat construction



The so-called Michael Überlager, compartment being opened

This module was later adapted also for application in the 'Wismar programm', meant for as to fit within various Würzburg apparatus, with simple, though effective, quick frequency tuning. A rather necessary provision, as after the Gomorrah raid on Hamburg (24/25 July 1943) extensive jamming was initiated since. However, the Germans got warned already after the Bruneval raid (February 1942) where British Special Forces, captured essential parts of an old Würzburg FuG 62 A. They therefore had already adapted some modules and soon many should follow. 



Viewing the module from the rear side



Mixer section being opened



Viewing the receiver part of this module



The final IF section being opened partly



Viewing the previous section from ahead



Viewing it from a different perspective 



Noticing the foregoing IF stages, viewed from above 



Within the square box we find the 1ste IF stage, mounted on top of the mixer module


Concluding with where it is all about

Bring the two modules and different techniques on display



On the left-hand side we see the Michael receiver module

This module being mounted at a rotatable platform 



Concluding this rather heavy loaded web page with the Stuttgart receiver module Fu G 03 / III

Displaying it dismantled, because it is in a rather poor condition. As to keep things attractive, we decided to accomplish it this way.

Allowing that one can look at modules more closely than is the case with the integrated Michael module (Einschub)


If there is someone having additional information or knowledge, please come forward and contact us.

Please type in what you read.


By Arthur O. Bauer