Abstimm- oder Anschlusseinsatz a

Extended on: 13-15 June 2015

Minor adaptation has been accomplished on 13 October 2016

Important correction and additional information

1 + 1a + 2b



Type Abst. a

Nr. 4461

Baujahr 1943



Front panel of the Abstimmsatz type a



This list has been made by Detlev Bölte DJ1LP


During a meeting held in Bückeburg near Minden (Westfalen) on 23-26 April 2015, Detlev asked me, whether I know the Abstimmeinsatz a? Yes, I do.

Followed by a discussion on aspects of this quite mysterious device. He gave me the above reproduced list, on which the Abstimmeinsatz is dealt with on the left-hand side column. The right-hand column concerns a different apparatus which was meant to match the 15 WS onto a symmetric antenna. Some suggest, erroneously, that the Abstimmeinsatz a was meant for tuning the 15 WS.


As to let speak the tuning dial for itself:




This photo has been taken from a perspective where the linkage onto its real purpose is clearly visible

Torn.Fu.    b1 und f

Quite clear, this device is to be operated in conjunction to Torn Fu b1 or f

Apparently, the tuning goes from 3000 kHz up to 6500 kHz.

Both are low power man-pack sets; although, operation normally is maintained stationary.

On 9 May Detlev Bölte provided a poor, but most useful copy of D1790/2. In which they extend the application of Abst a

To: Tornisterfunkgeräte b1, f. and g*, k

Quite understandable, because these all operate in the same wave spectrum

* Torn Fu k is like the Torn Fu b1 and f, but equipped with 2.4 V valves and a rather complicated power supply. Torn Fu g is a back-pack set, also used for moving operations. I even once saw a photo where the Torn Fu g was used inside a tank (Tiger Panzer?). Likely for communicating with 'Panzer-Grenadiere'. Torn Fu k was also known as 'Karl Gerät'.


Before continuing with the photo series, we should consider the schematic I once drew in January 1990



This was the first drawing which came into being from following the wiring of this ominous set Please notice the circuit corrections some drawings below

The way the transmitter energy being measured remembers me to the way power can be measured, as the current induced into the secondary transformer windings is a function of the current flowing in the primary windings.



As to get it better understandable, I re-drew it slightly for your convenience (1990)

Corrections necessary

On 9 May 2015, I received an e-mail from Detlev Bölte, who kindly provided some paper copies of manual D 1790/2.



It becomes clear, that my drawn schematic is not entirely correct

The major point is the way the secondary winding of transformer Î being interconnected.

What becomes, nevertheless, apparent, is the way power being indicated. It clearly is a summation of an antenna-voltage- as well as antenna-current-measurement. Though, to be considered indicating a relative value, not an absolute one. 

Please notice also the extension down on this page


The connections onto the moving coil meter points-out that the meter mounted in our set is not genuine; as it should have a push-button for sensitive- and less-sensitive operation.

Please notice the strange curved disks, which are tuning the two different tuning-capacitors in accordance frequency; notice the tuning scale foregoing the two schematics.



This photo shows the tuning mechanism. The curved disks can also be seen. With some imagination even the shaft of the special tuning capacitor



It is apparent, that we do not deal with a regular 'rotation capacitor' though with a capacitance that is tuned by means of a vertical movement

In those days, Dutch Philips brought these capacitor types to a great science. The main difficulty was - reproducing the vertical movement into a particular accurate capacitance value reliably. 


Another aspect is the second usage of this device.

It could also be operated in conjunction to 'bunker' operation. In this case the set could also control the operation of the special outside antenna arrangement. For it the two most right-hand connections 1 and 5 had to be operated. This connection is to be find at the bottom of the set.



The most left-hand side connection was only connected onto when the set was mounted in a special heavy box; having a special glass window lid

The connection down left might be the connection number 5, which equals ground.

The real function of A and B is not yet known as the manual D1790/1 has to be taken from our Klooster archives. Please consider what has been found down on this webpage.



Intriguing is the small window showing the number two, which is inter-connected onto the next shown mechanism


On 9 May I got a copy of D 1790/2 in which is explained that the number 1, 2 or 3 do correspond with the actual coaxial cable length between the die cast box (see below) and the foot of the aerial of respectively 15, 22.5 or 30 metres.

Please notice also the extension down this webpage



It apparently is linked onto this mechanism

Due to the fact that until now we do not possess its manual, I cannot explain more details.



Maybe this photo explains better what the curved tuning disks are about

It also shows the disk-curve and the tuning capacitor response.

The various disks may be linked to the coaxial cable length concerned. My guess, that curved-disk-arrangement can be moved up and down the shaft. So that the two tuning capacitors get a different - frequency versus cable-length response.



Viewing now the opposite side of this module


'BA 17' might indicate that it was accepted on behalf of the GAF, although, its application might have been mainly operated by the German army (Heer).



Viewing the electrical section. The connector on the left was to interconnect a Torn Fu b1 or f onto Abstimmsatz a

Sirutor was a Siemens diode, with special characteristics but mainly for low voltage and low power HF applications. In those days, widely found in German equipment.



Position number '1' constitutes the HF transformer, which can be aligned

A typical Siemens & Halske product. In those days pot-cores, but based on 'dust core', was a common device and widely used in Germany. I once compared post-war pot-cores (ferrite) with the wartime devices, and their common appearance is striking!

Not always known, some, what became world standard, had its origin from German techniques. The famous Amphenol edge connectors went back to the so-called 'List-Stecker'. Also the robust Tuchel connectors with their un-beatable contact reliability is also a good example. The Tuchel company was later purchased by the Amphenol Company.



In the meantime I have copied the two concerned manual we have.



The special box is constructed rather rigid en is drawn below from memory, as I have seen once about 40 years ago


Added on 24 May 2015

The text onto the above shown drawing provides:

We can learn: FJD stood for: Funk-Innenanschlußdose*

* In German language: J may also stand for i or I; sometimes causing confusion among non German-speaking people.

What we should not neglect, bunker systems possessed a gas-tight environment. Thus, also cables should have been laid such, that gas could not penetrate the bunker interior. Most bunkers possessed for it a special, a so-called, 'gas-lock'.


I guess, although this drawing has some shortcomings, that what it should be about is understandable

Particularly when we compare the foregoing and the above drawings.

Whether the box design was to prevent it from environment or to prevent that someone can change the 'Absitmmeinsatz a' settings, I don't know.

From the new findings described below, we learn that at the bottom of the 'die cast box'(above) there are also provisions for matching onto the actual coaxial cable length concerned (15, 22.5 or 30 metres). 


On Saturday 9 May 2015,

Detlev Bölte provided a copy of what he regarded being a most poor copy of manual D1790/2 



The top of this drawing is showing the rear side of Abstimmeinsatz a



What can we learn from this text?

That they had to deal with a coaxial cable length of 15, 22.5 or 30 meter cable length. Cable impedance given 60 Ω.   Wave-length is now given for: 120 m up to 45 m.



This point into the direction of that the cable length being in some relation onto the wave-band concerned. Jumping onto the information that matching is being accomplished by means of special presetting of the two tuning capacitors


Following the text above

Nach Aufschrauben der Schraube A wird die durch diese festgehaltene Kappe B nach rechts zur Seite geschoben und dann die Schraube C gedreht, bis in der Öffnung rechts unterhalb (hier oberhalb, AOB) die Zahl 1, 2 oder 3 erscheint. Diese Zahlen sind die Kabellängen von 15, 22.5 bzw. 30 m zugeordnet.



This latter page is explaining how the rear-side setting of the Abst-a module has to match onto the three different cable lengths



In the manual at the last page they quote:

Bei Erscheinen einer der Zahlen 1-3 (shown above, AOB) wird gleichzeitig eine der drei kleinen Öffnungen unterhalb der C freigegeben. In diese paßt der einsprechende Stift in der Funkinnenanschlußdose nur dann, wenn dort die gleiche Zahl sichtbar is

Montage hinweis: Bei Einbau des Abstimmeinsatzes a in die Funkinnenanschlußdose (see the drawn die cast box above, AOB) ist darauf zu achten, daß die auf seiner Rückseite sichtbare Zahl mit der auf dem Boden der Funkinnenanschlußdose stehenden Zahl übereinstimmt. Anderenfalls ist die Einstellung Einstellung des Abstimmeinsatzes a, wie oben beschrieben vor zu nehmen.




Abstimmeinsatz a had two optional functions.


D 1790/1    Merkblatt für den Aufbau von Truppenfunkgerät und Behilfsantennen in standigen Anlagen der Landesbefestigung    vom 1.10.42

D 1790/5    Richtlinien für den Aufbau von Behelsantennen in Festungsanlagen     vom 1.10.43

D 1790/6    Richtlinien für Einsatz, Bedienung und Aufbau der Festungsantenne aller Art  vom 1.11.1944



On 13-15 June 2015

On special request: the name has been abbreviated on 13 October 2016

Saturday 13th, Mr D. Z. did visit us and brought along the so desperately searched for FJD box. Designed for application within bunkers in conjunction to low power transceivers (transmitter combined with a receiver).

I was allowed taking pictures as to clear remaining mysterious queries.

And we found one, so far I know, nowhere else described yet on the web.



Funkinnenanschlussdose (closed tightly)

This heavy cast iron module is apparently in a quite good shape and having still its genuine paint.

The lid should be kept closed, we later will see how and notice why.

The high frequency-high-voltage (danger) sign is ridicule in respect to the expected voltage, as we deal with HF powers of less than 3 watt. I guess, it should prevent for unauthorized access. 



What do we see?

A simplified provision, replacing our rather complicated Abstimmeinsatz a. During a recent excursion in the dunes around Wijk aan Zee, the group leader mentioned that about 15,000 bunkers being built for the 'Atlanikwall'. Of course, not every one being equipped with radio-communication. Let us estimate every 20th bunker having an FJD provision. This would mean that about 750 units should be provided. Having discussed on this webpage the rather complex mechanism of the Abstimmeinsatz a, it is quite understandable that in, say, 1944, they went for a more simple, call it crude, 'Ersatz'.



And simple it is!

Only a piece of coaxial cable; likely having 60 Ω impedance, as this figure is mentioned in one of the  previous manuals.  On this photo below, we see on the right-hand side the coaxial interconnection between this module and 'Abstimmeinsatz a' straight away leading to the antenna (through an additional coaxial connector).



On the right-hand side we see the coaxial-input (the output of 'Abstimmeinsatz a') leading onto the outside antenna. In this case being fed via the coaxial interconnection of the 'Ersatz' module



The circular disk is of unexpected relevance.

Previously we have learned that the number at the back of the 'Abstimmeinsatz a' must correlate with a number at the bottom of the FJD box. But what does this imply?



Before the 'Abstimmeinsatz a' could be sunk into the FJD box, both numbers should be adjusted to match. Consequently, the number at the back-side of the 'Abstimmeinsatz a' should be selected accordingly, as to correlate with the one provided at the bottom of the FJD box

Please compare it with the brief drawing below



Comparing both this drawing and the previous photo we can see that the disk is about

Please notice, that the vector of the dotted sector being my guess, it actually might concern another vector; however, its basic function stays equal.

The sector marked 1 means, according information provided in one of the manuals above, that the bunker where this FJD device once was captured from, operated a coaxial cable length of 15 m. Number 2 should have stood for 22.5 m, and number three for 30 m cable length.

For me quite unexpected, is the application of a screw-pin. For it can be find a counter-hole in the back of the 'Abstimmeinsatz a' module. In this case just left of the counter-number 1 visible at the backside of the 'Abstimmeinsatz a'.



Though, when both settings do not match, the non-matching-holes being blocked; and 'Abstimmeinsatz a' cannot be 'sunk' into the FJD box entirely

Please bear in mind my later comment, and notice that there has been left no free space for cables or wires between the 'Abstimmeinsatz a' housing and the inside wall of the FJD case.



The glass window allows watching the power meter response (during transmission)

I wondered first, that there does not exist a provision for the cable input originating from, for instance, a Torn Fu B1. As the three Bakelite black heads do not allow access of wires (cable) due to missing free space space between the internal box-walls and the 'Abstimmeinsatz a' mounted inside the FJD housing.


Mr D. Z. pointed at a provision, not noticed in first instance.


These rubber seals were used as to provide a more or less gas-tight barrier, shown in the next photo - the top-lid being closed with quite some force (pressure)



Pressure-lock closed, but not yet forced together

The cable facing towards us, is the cut-off coaxial cable to the out side bunker antenna.

I therefore guess, that instead of a coaxial cable two separate insulated wires were once operated. It is quite clear, that the previously shown 'Ersatz' module is not optimally matching onto the antenna output circuit of a Torn Fu b1 or that like.  



The quite simple coaxial-connector left of the FJD box



The coaxial connectors solely




By Arthur O. Bauer


Please notice also the test set for the: Torn Fu b1 and f receiver and transmitter