The seemingly never ending

Nachtfee Saga

Page initiated: 1 December 2013

Status: 11/12 September 2014

2b New document found

3 Additional information on operational Nachtfee

4a Marcel answered on a series of queries

5b Recent eDEN dealt with operation Martha + I received a restoration award which I received during the annual Autumn Symposium of DEHS (Shrivenham)



In the current ongoing Felkin Report transcripts, Helwig Schmied and his colleague just recently did send me a new file A.D.I. (K) 175/45 which is an extension of A.D.I. (K) 142/45

I would honestly speaking have thought that the conclusion of our Nachtfee survey is being reached. This seemingly is not the case.

For the full transcript of this consideration please read first: A.D.I. (K) 175/45

Let us digest the following paragraph quoting from the interrogations of the crew of the on 23rd January 1945 shot down German Pathfinder aircraft type Ju88 8-3 carrying the designation Z6+FH:


28. P/W themselves had received a certain amount of

theoretical instruction during January but only one of them -

the W/T operator - had seen the "Y" clock. They were to have

received airborne instruction on January 25th and 26th flying

over the North Sea one northerly course from Leeuwarden; it

was thought that the necessary airborne instruction could last

about 8-10 days in all and that early in March aircraft of the

Staffel would be ready to use the new procedure operationally

over the front line areas.

What does mean "Y" clock?

This is curious, and I would like to think of the control screen of the aircraft Nachtfee.

This following text is in accordance to this. There exists an apparent mixing up between "Y" and the EGON procedure on which Nachtfee had to rely.


The New "X" Procedure.

26. This new procedure is basically a combination of the "Y"

beam and the Egon procedure. A "Y" beam - referred to by P/W

as "Oskar"; the code name known to have been applied to the

original "Y" beam used in 1940 - is employed in conjunction

with the FuGe 28, the FuGe 25a and a clock which P/W called

the "Y" clock, but which appears from their description to be

similar in principle to, if not identical with, the "clock"

reported in April 1944 as having been devised for the Egon

procedure. (A.D.I.(K) 160/1944).


34. P/W did not know the FuGe number of this instrument and

none of them, with the exception of the W/T operator, had

heard any other name for it than the "Y" clock; the latter had

once or twice heard it referred to as the SNK-Gerät, but he

had no idea what these initials denoted.


The 'order' or Command SNK (@ 330 degrees) definitely points on to a Nachtfee instruction

Shown is the ground control compass; where 'snk' stood for 'Schnecke' or reduce your speed.


35. The description given by P/W is strikingly similar to that

contained in A.D.I.(K) 160/1944 paras. 29-36. Basically the

clock consists of a cathode ray tube screen about 20 cm. in

diameter with numbers from 0 to 9 spaced at intervals round

its circumference. Each of these numbers denotes a code

instruction, the significance of which is given on the W/T

briefing sheet for each operation and is varied from sortie to

Please notice the mixing up of Y and the aircraft cathode ray tube. Definitely meaning the Nachtfee 'order' or Command CRT


38. The "hand" of the look appears as a wedge-shaped blip on

the screen of the Cathode ray tube about two-thirds out from

its centre. It rests at a neutral position at twelve o'clock

and is moved to the various figures by means of impulses from

the ground station lasting only 1/100th of a second, and

therefore calculated by the Germans to be unjammable by us.

Can be there a doubt that what is described is matching to the next picture?


Shown is the ground equivalence of the CRT screen, which in my perception equals the LB2 CRT screen used in the Nachtfee ground console

Please notice, that we are looking at the control screen of the Nachtfee ground console. The signal due North is the Nachtfee 'order' signal due in its waiting position. The other signal is representing the aircraft time reference signal in our case designated TB. Repeating paragraph number 26:   


The New "X" Procedure.

26. This new procedure is basically a combination of the "Y"

beam and the Egon procedure. A "Y" beam - referred to by P/W

as "Oskar"; the code name known to have been applied to the

original "Y" beam used in 1940 - is employed in conjunction

with the FuGe 28, the FuGe 25a and a clock which P/W called

the "Y" clock, but which appears from their description to be

similar in principle to, if not identical with, the "clock"

reported in April 1944 as having been devised for the Egon

procedure. (A.D.I.(K) 160/1944).

Please compare this statement with the second previous photo.

An open question for us remains in conjunction to the due South 'order' 'Pauke' combined with the text: Auto. Stood 'Auto' for automatisch (automatic) or points 'Auto' towards the application of the X-Uhr (X-clock)? In the early war days the X-Uhr was used in conjunction to computing the exact moment of bomb release. It would have been enormous helpful when we would have had access to genuine German instruction or trainings syllables.

Also changing our perception a bit is the locations from which Nachtfee was operationally used - namely Leeuwarden, still today a Dutch military airbase.

The ongoing discussion is - what has happened with the German papers concerning Nachtfee? There is too much discrepancy between the frequency of Nachtfee related topics in British 1944 - 1945 reports that nothing was collected about the time Germany surrendered; especially viewing the currently total absence of technical information in British archives. It is for me impossible to visit the many places in the U.S. where information might be kept still. Britain archives disposed of nearly all of genuine German technical papers, in contrast to U.S. archival policy in post war days. 


7. In about October or November it had been known in K.G.66

that the Germans believed the Allies to be planning a largescale

landing in the Bay of Venice, suit that K.G.66 was to be

moved South to take part in a "Total Einsatz" (full-scale

operation) against it. The landing did not, however,



There are some indications that our Nachtfee console came from the area of Vienna and was supposed to guide some KG 66 pathfinder aircraft over northern Italy. Whether KG 66 was engaged here in Nachtfee techniques is not known to me. The only fact we have to count with is that our Nachtfee console came from the US. And, most likely, was captured by them somewhere in their occupied military zones.

We should also not forget, that the Nachtfee ground console was still in an experimental stage of development. We still don't know whether the system suffered from technical shortcomings, like the too high standard of the time bases involved (10-7), or that personnel training was the bottleneck; or both.  


On 23+25 March 2014


On 23rd I got an e-mail from René Voulon from Holland, who very kindly did send me a few pages of a genuine German wartime document. Particularly rare as it is the first genuine text I got on Nachtfee. 


For your better understanding and making the content of this document searchable I will transcribe the text

"EGON 2"    ist ein in Entwicklung befindliches neuere "Egon - Verfahren."

Es soll durchgeführt werden mit:

Wassermann - Einsatz und Schnittpeilung.

Auserdem wird dafür ein neuer Erstling mit ca. 800 Watt Senderstrahlungsleistung und ein neues Kommandogerät ("Nachtfee") entwickelt.

Da die Befehlsübertragung über den Boden - Bord - Funksprechverkehr mittels Fu. G 16 vom Gegner meist stark gestürt wird, so soll das neue Kommandogerät Nachtfee die Befehlsübermittlung etwas auf folgende weise ermöglichen:

    Das Freya - Gerät hat eine Summerspannung 500 hz. Es sendet also 500 Impulse / sec. aus. Diese 500 Impulse werden zur Messung des Flugzieles eigentlich nicht alle benötigt.  Es werden daher ca. 100 Impulse für die Befehlsübermittlung davon abgezweigt, welche nach einem bestimmten System mit Hilfe von Phasenschiebern eine grössere Anzahl Impulsveriationen zulassen. Diese dann sich ergebenden rythmischen Impulsbilder werden auf ein Braunsches Rohr gegeben, so dass die entstehenden Zackenbilder an Messmarken als übertragende Befehle und Kommandos abzulesen sind.*

* There exists, however, a contradiction, as the Nachtfee console by its own means generate the full number of 500 pulses/second. Bringing this fact in line with the description above - the divider or call it interrupter must then be somewhere inside the Freya-EGON system. On the other hand, we must also remember what is quoted in a R.V. Jones A.D.I. (Sc) report: 

However, this quotation does not directly points onto an interrupted Freya-EGON mode, as in my understanding in some way or another 500 Hz PRF must be kept coherent as the Nachtfee system cannot operate otherwise.

What might have been done, is that the 500 Hz PRF originating from the Nachtfee console is being interrupted; in this case coherence is still maintained. 


Nevertheless, this information is for us really significant! It proves that my previous assessments are correct. Things done 2, where I bring the proof that Nachtfee can proper operate with far less pulses than those used in conjunction to Freya's-EGON 500 Hz PRF.

A second implication heavily discussed, they intended to introduce a special modified FuG25a, where the transponder transmitter should get 800 Watt power. Such a modification might also having made it possible to provide special data in- and output connections. Whether they have commenced this new design, regarding their current wartime situation, is highly doubtful. Nevertheless, a re-design might have been possible.

We may consider this is a document from late 1943 or somewhere in 1944; especially bearing in mind what is mentioned in the Allied translation of Funkmessnachrichten 19 issued on 25 February 1945. Also known as: Radar News 19, by the way this paper being the nucleus of our entire Nachtfee survey!     



On 4 September 2013


Today I received an e-mail from Marcel who some years ago interviewed two former K.G. 66 'Beobachter' (observers or navigator operators)

On request, quoting from Marcel's e-mail of 3 September:

He refers to an 'observer' crew member of KG/66 who flew with Ju 88 S-1; and explains roughly what provision were taken as to enhance the latter aircraft performance. Its aim was to allow operations between 8 to 10 km altitude. Not essential armament was removed as to reduce its flying-weight. He also explained why Do 217 K and M type were not suitable (less manoeuvrable)

Also apparent, the first tactical Nachtfee employment was during the so-called Baby Blitz on London of January - April 1944. The German code name was: Unternehmen Steinbock

Also of great interest: that the logbook of the 'Beobachter' states, that on 14 October 1943 there was held a so-called 'Einbaubesprechung' (meeting on fitting the new navigational gear, like was Nachtfee and/or GEE). To what I understand: flights were arranged from Montdidier to Köthen and Rechlin several times. Rechlin was the main GAF research centre, where likely Nachtfee was developed by Dipl.-ing. T. von Hauteville (E-4).

During the interview the 'Beobachter' couldn't remember what particular navigational gear he had dealt with, but Marcel can remember that the word Nachtfee once felt. We know, so far, that K.G. I/66 flew, for some time,  with Nachtfee and that K.G. 5/66 operated original British GEE gear. Apparently, GEE (German code-name Truhe) operated rather reliably and it was counter productive to jam it; as by this means they would have interfered directly their own navigational aid (GEE).


Nachtfee signals were also using the I.F.F signal carrier, which operated in a frequency spectrum not too far from British systems, like their own IFF.




On 11/12 September 2014


I received rather interesting information on pathfinder aircraft likely used by K.G 1/66 and 5/66. Just when writing this text section, it appeared in my brains, that K.G. I/66 was operating for some time with Nachtfee and apparently thereafter with Truhe mainly. Truhe was the German code-name to the British equivalence of GEE. In most cases, they used British modules entirely (bear in mind that thousands of British aircraft crashed on German controlled soil during the war); although, a Telefunken derivate existed. In effect, these modules were sufficiently at hand; and, could hardly be jammed or otherwise hampered, as they would then themselves hamper GEE navigation over Britain. Operating Y-Kampf is not likely, because 'Benito' was heavily jammed and, although, providing bearings, at ranges of, say, 250 km, it over-stretched its reliability.  For better understanding, please notice my paper on Navigational Aids (PDF page 12+).

One aspect is in the latter situation challenging, because Nachtfee provided, for example, running information on speed, as to stay synchronised with the following bomber stream (the time lapse that flares stay visual is maximally 8-9 minutes), when, for what ever reason, the bomber stream was delayed, flare droppings should be repeated. For this occasion, the aircraft was by Nachtfee means instructed to fly a circle or in German military jargon Karussel, abbriviated 'kus'. Also other instructions were being passed onto them. Consider: Nachtfee new findings.  However, they could have operated Morse keyed IFF signals.  (please notice further down Fig. 6 and 7) Considering first the next 'order' or Command scale, left to 'kus' we find 'knh'. Hypothetically, the 'h' might have meant 'Höhe' (height); whilst 'k' could have stood for Kurs or Kampf. Another option: Kommando-Höhe, but then somewhere an altitude should also be conveyed, or, primarily  a tactical height was being 'briefed' upon in advance. However, I previously suggested knh could have stood for: 'komm nach hause", I know, this sounds silly, but still not unlikely. Please notice, that the latter suggestions are my guesses only!    




Viewing the 'order' or command compass (under restoration in December 2011)



 Ju 88 S-1, used by K.G. 66

(Photo by courtesy of Marcel van Heijkop)

He also mentions: that the tail tip apparently had been repaired. It has to be noticed too, that he did send me an additional photo, where the Ju 88 S-1's tail was lacking the regular swastika, the entire aircraft instead being pained in grey/white dots. For details he refers to:

Unlike Ju 88 generally, this type had a crew of 3 men.

Please, just noticing it, the white rod at the under-belly of the fuselage - is the FuG 25a antenna to the I.F.F (IFF) as was also additionally operated by Nachtfee. Please bear in mind, that Nachtfee signals were using the same signal carrier as did the FuG 25a IFF.

This photo will, however, not prove that it concerns a Nachtfee pathfinder. What it does, is showing at least a similar aircraft. Nevertheless, this type was flown by I/K.G. 66.


Marcel pointed briefly: that Ju 88 S-1 operated often at levels between 8 to 10 km. The BMW (Stern) engines were additionally fit with GM1, a provision to increase additional oxygen. After mid 1944, these aircraft got different engines; type JUMO 213 and their type number changed in Ju 88 S-3

We likely have a manual on the Jumo 213 engine, which was a Diesel power-source,  of a very curious construction.

Quoting secondly, briefly: The person I knew was an 'observer' (Stab/K.G.66) and flew during Operation Steinbock only with Ju 88 S-1 aircraft. This type was specially adapted for Pathfinder operations. ... The D0 217 K/M proved not suitable for serving as a Pathfinder. One reason, it was to bulky and heavy. 

Quoting from another paragraph: According Marcel, but not entirely in accordance to R.V. Jones' A.D.I. 101 (Sc), who quotes K.G. I/66, was it 5./KG66 who were the EGON, thus Freya-EGON (Nachtfee FuG 136). He bears from memory with some reserves: After changing several tactical designations, becoming the: Ergänzungsstaffel in Germany (Staußberg/Greifswald) The 3rd Staffel was then operating as SIGINT or in German nomenclature: "Hör- und Störstaffel". (Stör means: jamming) Although, he states: That the latter Staffel was organically part of KG66, it had, nevertheless, operationally nothing to do with KG66. It operated from a different air base (Corneilles-en-Vexin); also crews did not mix up.

However: the 2nd Staffel soon became (end of 1943-begin 1944) the Truhe Staffel; the latter is equal to British GEE navigational aid.

During Operation Steinbock (Baby-Blitz), several navigational aids were, for tactical reasons, involved; as to hamper British counter measures.. In my perception, Truhe (GEE) was the most promising, but lacked the important feature of being guided in a tactical sense. Thus, getting instructions from the controlling Freya-EGON ground station. Please notice down the drawings Fig. 6 and Figure 7.

We have to be grateful, that Marcel have had in the past contact to someone who actually has been engaged with operations of K.G. 66.   He has a copy of at least one crew flight-logbook.

Rereading again the already used text. What is noticeable, is the fact of stripping down all armour where possible and also removing weapons; as to allow operations at greater height and speed.



Viewing both Figure 6 and 7 of Radar News 16

(drawing originating from the genuine Radar News 19 file PRO/NA)

Figure 6 is constituting the Freya-EGON Nachtfee system; Fig. 7 is employing still Freya-EGON signal-carrier, but now in conjunction with a much simpler technique, where the FuG 25a IFF 'order' or Command signals being Morse-keyed towards a guided aircraft. In my perception, less secure, and might causing confusion, because at least not easy to steer a single aircraft out of several. On the other hand its system is demanding far less advanced technologies.

It might thus have been possible, that one of the Staffel relied upon acoustical 'Barbara'.

What we, however, never should forget, is the fact that one of the reasons for developing Nachtfee and later the adoption of Barbara (FuG 139), was that British jamming had become a nuisance; and Nachtfee was introduced as to cope with it, and making SIGINT impossible. Why, because Nachtfee relied entirely upon  coherent signals in the domain of time, where speed and range was constantly controlled upon. Only signal comparison within the Nachtfee ground control was possible. False signals were not synchronised upon. As the upward and downward signal-paths are equal. What the British called 'meaconing' was only possible if such jammer was about adjacent to the actual German Pathfinder aircraft. Sending meaconing signals from other stations would always be recognised. Please bear in mind, both distance and bearing was controlled manually by the Nachtfee console operators constantly; Freya-EGON operated on a narrow antenna beam. Signals could only be received within its antenna aperture.  Nachtfee 'order' or command signals acted always in coherence, which was impossible by all other signals interfering; therefore never passing on false 'order' or command instructions. Saturating the FuG 25a transponder function was, of course, possible, causing a 'blackout' of signal transfer. In one of the Felkin reports, was stated: that false signals could bring the Pathfinder aircraft 'order' display out-of-synchronism, which it could not. The one who wrote this down apparently did not grasp the way Nachtfee worked.        



On 1st  October 2014 + 7 October 2014

Phil Judkins quoted on eDEN page 24:

Quoting: On Xmas Eve 1944, Operation Martha, a German attempt to attack Manchester with 50 V1s from Heinkel (He 111, AOB) bombers off Spurn Head, brought northern England into the into the robot war.  The attack was a failure - only one missile got into Manchester, though some casualties resulted - but note that many of the missiles passed over to Todmorden, John Cockcroft's home town and that of his family; doubtless, a cause for thought. 

Photo copied from eDEN

The above statement on Martha is in most respect in accordance to what is stated in Felkin's:

A.D.I. (K) 175/45


On 7 October 2014


On 7 October 2014, the Defence Electronics History Society gave me an Award for all the commitment put into unrevealing the secrets of the mysterious FuG 136 Nachtfee system; and bringing it to operate again, but also to understand where its principles rely upon. Albeit, for obvious reasons, demonstrating it at very limited range (but operating fully) in conjunction to a simulated aircraft display system.


To be continued in due course  

By Arthur O. Bauer