Unknown Watson-Watt like display



Page initiated: 13 May 2022

Current page status: 28 June 2022

Section 2  (17 May 2022)

Section 3  (20 May 2022)

Section 4  (27 May 2022)

Section 5:  (3 June 2022)

Section 6  (17 June 2022)

Section 7  (28 June 2022)

(2) A view days ago we have obtained this curious apparatus, from France

What does it constitute?


My first thoughts were about a two channel system like:  East-West and North-South HF (RF) apparatus.


Let us consider, albeit in another succession as was planned before:

But this morning, still in bed, I considered in contrast to my first thoughts:



(13) Let us notice the valves (tubes):

EF 14 a high-slope valve followed by

two stages EF 12

followed by two stages EF 14

The type EF 12 was a pentode valve used mainly for audio applications.


My first thought went in to the direction of HF Watson-Watt like direction finding applications.

But, there does not exist, at least in this apparatus, a means of frequency tuning.

But the EF 12 valve type was meant for audio applications; therefore I now tend to believe that our apparatus

being meant as a 4 channel audio Direction-Finding indicator system; based upon the Watson-Watt principle.



(1 gif) This briefly is, in my perception, what its principle is about

Please view the next photo again; then the numbers I and II might be considered, in our principle, the two left and right channels connected onto the horizontal plates;

whereas the vertical plate being connected onto the channel III and IV


The numbers might have been towards the axis planes different; but it principally must have function like this way.

Whether the signal sources were microphones (sound sensors) or other means I cannot yet say.



(2) Consequently: only the application of EF 12 valves may well limit the expected frequency spectrum towards the audio spectrum; or we may expect operation within the ultra-sonic spectrum too

What is also supporting my explanation - is the "Lautstärke" (loudness) control as well as the application of a double "headphone" (Telefon) outputs;

its three pin connection - is at least - strongly pointing at a naval (Kriegsmarine) application; albeit, that the regular GAF (Luftwaffe) or Army (Heer) headphones could be connected as well. 


These findings will, consequently, force me to switch this apparatus on - thus connecting it onto the mains; as to investigate its actual frequency spectrum (Deo volente).

Whether it will be even possible to produce a real Lissajous presentation, I cannot predict yet.



(1) What did trigger my attention was: the module with the 10 German "steel valves" which, for some years, I had exchanged with someone



(13) I did obtain two modules the one still in reasonable (outside) condition

It is evident, that both amplifier chains being similar.

What I previously did not realise, was that it constituted two equal channels.


(7) Maybe of some interest is, the notice that our device still is being fit with the genuine wartime valves,

visible by the rectangular stamp carrying: Wehrmacht



(14) Viewing now the left-hand side section

It is quite visible that also these two modules once were equal, but that the lower module had been changed once.


The question might be razed: doesn't constitute these devices of a post war manufacture?


Most likely, it was a late, but wartime product.

Why, I am so certain?

Some time ago, an article appeared in the German amateur periodical Funkgeschichte of the GFGF; written by a Mr. Müller; about a wartime assemblage company near Bludenz in Austria a bit east of Feldkirch.

I was so astonished about two photos, of which one was about this set, during assemblage.

The next one showed a different device: a unit incorporating the "KUH" IFF transmitter, but it might have been in a Kriegsmarine (German Navy) version.

However, for some months I kept this particular issue in my hands, but, for what ever reason, I don't know where I did store it!



(10) For the freaks among us, viewing from the bottom side it is visible how the 4 channel-connectors (I .. IV) could be mounted rigidly by means of 4 screws

One side of the "spot-welled" grip might behave been broken-off, due to the fact that the French might have used an unsuitable housing, which heavily hampered its pulling-out with little force.



(15) Finally for today, we view our module next to the complete set

The adjusting controls III and IV are clearly visible under (down of) the two coaxial connectors.

With some imagination, you might understand how the right-hand module fits inside the left-hand main module


(9) Please view at the top ends of the red resistors, where you notice the typical way the German military electronics marked their resistors

The yellow cables were used quite regularly in German military Naval and also GAF (Luftwaffe) gear.

The outside was a kind of linen? covered by a kind of a thin transparent plastic (PVC?) layer, and, in my perception, also heat resisting.

As it was quite often found in Philips products made for the Germans, I therefore would not wonder that it once had been manufactured by Philips or a related manufacturer.

(2)  (17 May 2022)



On 16th May I, very kindly, received from Ingo Pötschke (the Chairman of the GFGF) some copies of the GFGF page (Funkgeschichte 251) dealing with our apparatus.


I my perception the most relevant information is: that North-South being constituted by, respectively, the channels  I and II (please, view up and down the CRT screen)

Where we may assume that  I  actually is constituting North

Additionally: it could also have meant fore and aft of a vessel (ship)



(3)  (20 May 2022)

My next move today was to switch on the entire unknown apparatus

Of course, firstly by means of a lamp (230 V light bulb) in series, as to view whether our apparatus is overloaded due to its faulty circuitry.

Which wasn't the case, and the lamp had been bridged by means of a switch.

HT was measured, but still no signal visible on the CRT screen.

I firstly removed a LB 8 CRT from another just obtained apparatus and exchanged it.

Now, at least we notice a spot; which is to be expected when no signal being fed onto the 4 channels marked: I   II   III and IV.


After having increased the amplification levels by means of the four controls accessible down on the front-panel, which are visibly connected with four arrows placed in a square. 


The succession of the four amplification controls are quite well indicated

By the way - the four heavy coaxial connectors are Kriegsmarine like; think also of LO 6 K/L 39



Wow, at least we notice a signal!



Its lower amplitude does not imply a  lower signal amplitude but it is being caused by the frequency response of the amplifier band-pass characteristic!



This amplitude is resulting at a generator frequency of ca. 1 kHz



This response is mainly being caused by the supplied signal frequency

Why it is behaving like this, I don't know yet.

We have reached the following status:

Thirdly, I tested all valves (tubes) concerned.

I measured first on our wartime RPG 3/4 valve tester all EF 14 valves concerned (8 valves). The first valve in channel 'I' type EF 14 did not respond at all!

Thereafter I tested all EF 12 valves, which all were emitting such that at least enough amplification should possibly achieved.

The only option remaining - is to remove the right-hand side module dedicated to the channels 'III' and 'IV'.

Figuring out, as to how it should be demounted, wasn't easy, but Hans Goulooze pointed rightly at two 'red marked' screws which solved the problem ultimately.


I was quite astonished viewing the high quality (soundness) of the employed components, especially considering that it might have been assembled in late 1944 or even early 1945!

All hermitically sealed-off capacitors, of which we may expect that these perform, after say 77/78 years, still according their genuine specifications!

The cylindrical capacitors were know as: type Sikatrop (Siemens tropical, hermetically sealed-off, types). (http://www.cdvandt.org/Siemens-Sikatrop-low.pdf)


What is also of interest, and likely will wonder quite many of you: at least blue the cable insulation being made of PVC!  We may expect that the yellow and brown cables being insulated by means of PVC as well.

The Germans possessed a very sophisticated chemical industry; such as IG Farben Industrie one of the biggest industries (conglomerate) world wide!


Viewing it from a bit different perspective


My next move should be: finding-out which connector is supplying the 6.3 V filament

Thereafter the pin or pins supplying the HT voltages and what are the signal output pins?

The coaxial input connections being all accessible at the front-panel.

We also should bear in mind, that the CRT HT, let us say, necessarily, between 1 and 2 kV; which I believe that currently does not exceed ca. 600 V.

But our first concern being to get the amplifier channels 'III' and 'IV' operational again.


YouTube films

Film 00108:    We are viewing the first responses, visible at the I (firstly, call it North) channel; started with, say 20 - 30 kHz - generating the maximum amplitude on the CRT screen. 3kHz is at least indicating that the frequency response is far beyond (lower) than the optimal spectrum of at about 20 ... 30 kHz.

Film 00109:    Please notice the centre spot; where no signal (amplitude) being indicated. Viewing at a signal frequency of about 30 kHz. It is evident, that we have to deal with the non, or poorly, responding amplifier stages first. Viewing next one of the channels 'III' and 'IV' (East-West). We notice a minimal response; which is, in my perception, equal to not functioning at all.  All amplifier valves concerned have been checked, and only a single valve (the first EF 14 stage of channel 'I') did not respond; but was still acting due to the correct functioning of the the following amplifiers (capacitive) involved. This valve, albeit placed in the EF 14 may have been defect, or even of a different type. After replacing it, the channel sensitively of channel 'I' increased enormously!



(4)  (27 May 2022)


On Thursday 26th May 2022, we continued our "unknown apparatus" Survey.


My first aim was to check electrically, the right-hand module designated (channel) III and IV.


As has previously already shown - it was necessary to dismantle the right-hand side module.


It didn't prove easy as to find out the various functions of the different module stages

Curious, the lowest section consists of two EF 14 (high-slope) valves. But it proved that it had only a single output and that, it might be, that both EF 14 valves being wired in some kind of a cascode circuitry; but

at this stage of our Survey, I am unable to understand its circuit implications soundly.


This, partly incomplete module I once obtained from Günter in late 2016

But, it actually proves of a great help, as it allows me to compare especially the various anode resistors; which is ultimately causing it entirely mall functioning of both channels III and IV.

In variously, almost all anode resistors were constituting an open circuit.

All were once produced by Always; a wartime Czech product of quite doubted quality.


By the way: I have to investigate more in detail where the yellow coloured wire from the EF 14 anode is connected onto in the far right-hand circuitry!

What I also should do: is to pull-out one of the EF 14 at the far right-hand side of this module, as to get an understanding what their actual function is in conjunction with the crt presentation.


I have added "parallel" resistors, which value could be determined (compared) with our incomplete module.

A quite pain-striking endeavour, which ended today successfully.


Rather confusing are the following findings; of which I would like to start with a principle schematics:



What was encountered, was striking:

I expected a "Watson-Watt" type display presentation, which actually isn't the case!

The Roman numbers, being identical with what is visible on the "unknown apparatus" front-panel.



Oh Eureka!

Entirely unexpected, channel IV is causing out-of centre a deflection, call it, west-wards;

please compare the foregoing drawing with the brief signal display now.

The tubular provision was necessary as to get rid of the interfering light entering via roof.


I am fully aware that what is being displayed is only valid for the time being.




Channel I is causing a deflection out-of the centre spot "north-wards";

a phenomenon already encountered during our first experiments.



Channel III is causing out-of centre a deflection "south wards"



The only channel still not operating is cannel II; which should cover the "centre east" deflection.

I therefore have removed the left-hand side module.

Quite astonishing me was the empty compartment on the far left-hand side.



Comparing makes all quite visible - below is our module obtained in 2016 and above we notice the empty left-hand side of the module

related to the channels I and II

Please view the upper module carefully:

Apparently, this channel (roman I) had already been dealt with before (likely in France); whereas the lower channel (roman II) of the upper module is still constituting the genuine state of affairs (as far it briefly is visible)

I, therefore, expect that also most anode-resistors being faulty.


Please be aware, that we encounter a mall functioning of the brightness circuitry; which we haven't yet focused upon as its wiring is difficult to trace.


YouTube Films:


Film 00110:    Today we repaired the right-hand side module concerning the channels (roman) III and IV. It proved that most of the anode resistors being faulty (due to late wartime quality). I was astonished that the channel IV is causing  a deflection from the centre to the left-hand side (horizontally). Whereas channel III is causing a screen presentation vertically downwards. In contrast, as we have noticed before, channel I is causing a vertical deflection upwards. 


Film 00111:    We are looking at the right-hand side module dedicated to the channels III and IV. Not yet understood - is the function of the two EF 14 valves seemingly in a kind or series circuitry, on the far right-hand side of this module.


Film 00112:    In front we look at the module we possess since late 2016, but I did not had the slightest idea where it belonged to. On the far right-hand side the ominous section which I do not understand its purpose yet.



(5)  (3 June 2022)


Today we encounter a quite brief report:

First: I had to repair channel II of the left-hand side module; which was managed after a quite complicated endeavour due to the extremely limited, accessible, space available.


It starts working in some respect, as not yet every signal channel is operating satisfactory.



At least we notice what might be theoretically expected when we feed both channels I and IV; from the same signal source



Maybe the next differently illuminated photo is providing you with a slightly better explanation



Only for your better understanding



Please remember what the implications are:

Feeding both channel IV on the far left-hand side in conjunction with channel I from a single signal source.



Though, now we consider the presentation between the channels II and III which does not provide the expected vector at, say, 135°

I must admit - that I don't know yet - why it does respond here like this.


(6)  (17 June 2022)


The about two weeks break has been caused by the fact that we have investigated more in detail the schematic of this curious apparatus.

Let us first reconsider some of my brief notes made in the recent past:


Notice 1: It all started quite basically

(kanaal = channel)


Notice 2:  (links = left - and rechts meant the right-hand side module/stages)

Voltages (630-670) were measured before the valves were constituting a substantial circuit load.

Quite some essentials were discovered today (16 June 2022)

Amongst it - that the the HT of ca. 615-615 V was also supplied at the two modules at line number 27 at both modules; the different values originate from the un-loaded and loaded conditions.

These voltages were from there also supplied onto the horizontal and vertical deflection plates.

AOB: I must admit, that I never could have expected that this could actually be the case.


Notice 2: The lower board with resistors is confusing me a bit

The shown board above being mounted under the metal crt screening body.

Actually, I measured about 7 à 8 V at the cathode; the LB 8 grid is connected onto the chassis by means of a 100 kΩ resistor


Viewing the LB 8 base from the rear-end

Z1 and Z2 and M1 and M2 are constituting the deflection plates

Each being, without signal drive being at a potential of ca. 610 - 615 V

Curious, is, that G (the crt grid) being connected to ground by means of a 100 kΩ resistor; whereas a capacitive coupling exists between the extra EF 14 stage in the right-hand module stage.

In my perception, likely constituting a "brightening" signal; however, which I haven't noticed yet.

The deflection plates sections  (Z1, Z2 and M1 and M2) being likely connected with the output EF 14s in each of the (left and right-hand) modules.

What is astonishing me, is that there exists only a positive G voltage of ca. 8 volts against ground.

Apparently quite much to be discovered yet.

We encountered in both modules annoying problems, maybe countered (but not yet fully proven) that in both module stages the filament grounds in the last EF 12s was sometimes behaving faulty.  


Measuring, by ohmic means, the actual crt connections and their origin in the existing circuitry

It might take some time before I am able to understand its circuitry comprehensively.


We only possess a single coaxial connector used  in conjunction with our current apparatus


Historically significant, is the fact that this connector fits perfectly; and that its origin pointing at the application in Kriegsmarine receivers Lo6K/L 39 and likely also in conjunction with the Main T9FK39 RX and others too

I approached one of the greatest collector in Europe - and he himself possesses only a few samples.




(7)    (28 June 2022)


The week next (after 17 June) I reconsidered the various queries and got the mood like I, sometimes, encountered during our long-lasting Nachtfee Survey.


Such as:


Please notice the potentiometer arm connected onto contact wire 38

Some of you will notice that we encounter only two potentiometer-connections.


Reconsidering our second module once obtained from a friend in 2016, it doesn't show any other connections onto g2 of the lower EF14 at the rear and of our apparatus; I consider it being the audio amplifier, as via its anode C 24 and is via cable number 37 wired onto the Kopfhörer (headphones) connector (at the front-panel) which signal I consider being audible.



The right-hand side potentiometer is shown in the next photograph



Viewing it from ground-connection: a and b (potentiometer arm) connected at wire 38 which is connected with g2 of the EF14 audio amplifier

I already noticed before that the Lautstärke (loudness control) does not respond.


My first approach was to measure the potentiometer resistance between both ends - thus the connections a and c.

I measured 100 kΩ

Therefore I implemented (and arbitrary guessed) that a resistor of 330 kΩ must do.

It was soon encountered that the potentiometer was responding as should be expected of an audio potentiometer;

but there existed, sometimes, a tendency of strange oscillation.

This could be countered by implementing an additional blocking capacitor of 0.4 µF.

But: there does not exists the slightest sign of an additional wire once; as well as board-connection (mounting) for these two additional components.



The only solution might be shown in the next drawing:

The not yet traced resistor inside the most rear module section isn't found yet



Considering our incomplete module

The screwdriver is pointing at C 24 the audio headphones coupling capacitor;

most down we just see the base of the audio EF14 valve base.


Just visible is towards the bottom of the chassis in the rear is a blue coloured (PVC) insulated wire, which is inter-connecting the EF14 g2 onto line 38 connector pin, and which ends at the audio-potentiometer-arm (Lautstärke).

The cylindrical capacitor-head (most down left) is the internal blocking capacitor at its opposite side connected onto g2 of the EF14 valve.

The actual components mounting is so extreme condense; consequently a component often cannot clearly be designated to what it is serving and wired onto.

Please remind:

They (the Germans) once mounted, for instance, a resistor at a pre-drilled - quite thin - 'pertinax' layer.

The wires at the other-side of the thin (carrying) layer being bended in such a way that it connects onto another components; these (blank) wires being kept insulated from the metal chassis by means of an even thinner pertinax strip.

Compare it as a pcb but now the wiring is substituted by the (normally existing) component-wires.

Its advantage was that one gets a rather flat and condense circuit wiring.

The nightmare starts when components do fail!

But the Germans lived under tremendous strain of getting very compact gear in combat.

Our next challenge will be whether I can determine this ominous resistor.


One direct query remains:

Why is the potentiometer connection 'c' clearly showing signs of pre-soldering?

In the second drawing I have interconnected line 38 with potentiometer connection 'c'.

This might have been the case.

Maybe some of the foregoing owners has cut the interconnecting wire.


Noticing the way channel 'I' once had been modified, his must have been accomplished by a well equipped and determined entity.

As the thin 'pertinax' layer being replaced by modern quality (epoxy) circuit boards, but wired like the Germans performed it in 1944/45.


Am I satisfied?


But this is the way surveys generally perform.


There exist more queries:

fore example - why do respond the combined quadrant-signals so differently?

Is this really (only) caused by the signal phase?

This would imply an almost impossible task to solve; as the according trimmer capacitors being built-in in such a way that the concerning compartments has to be dismantled entirely inclusive the most rear compartment shown next:


Please notice C 16 (visible just above the screw-driver shaft)

(please notice in the upper module that on the far left-hand side the 4 holes, once necessary as to built-in the trimmer mounting plates)

But the trimmer C 16 mounting plate being fixed by means of 2 x M 3 screws which are in between C 24 and the section wall.

Originally - at the most left-hand outer section there exist holes which allowed accessing the screw-heads, which now no longer be accessed. It is thus evident, that the trimmer being built-in at preliminary stage of assembling.     


This morning I gave it an additional thought: - most of the experiments had been maintained by touching the various contacts by my fingers which caused a 50 Hz (mains) hum (signal source).

I should accomplish first a wider reaching audio test series and noticing whether the resulting screen vectors do change much.

And noticing the responses between the two adjacent quadrants as is shown below.



Thus: measuring the combined frequency response between the channels:

 I and II

II and III

III and IV


IV and channel I

At least currently the expected signal vector between the channels III and IV do perform as may be expected that the resulting vector is about in between 180° and 270° thus about 225°.

Whether this is true over a wide audio spectrum even up to, say, 30 kHz is to be determined yet.

My aim is, that at least one quadrant is performing as maybe expected.


These experiments have to wait until after late of August.

To be continued in due course


Maybe someone possesses real information about this device / system.

There are indications, that someone, maybe in France, did modify channel I - by replacing some of the wires, and component-mountings, professionally.


Did have they actually employed it; and in what context?

 Therefore, please contact us at:



By Arthur O. Bauer