Hans Jucker's objections against my Nachtfee system reconstruction


Created 9 May 2012

Status: 18 May 2012



During a meeting in Dresden which took place between April  26 and 28, 2012, Hans Jucker expressed to me that he doesn't agree with my reconstruction of the Nachtfee system. I should apparently having made it work, but this wasn't done so during the war.


I have no idea where his knowledge is based upon, as there is no technical material around, or someone must have restricted its circulation.


It is found nevertheless - that nearly all Nachtfee secrets are incorporated somewhere in the Nachtfee consol concept.



I know Hans for quite a while and this is the reason why I have to deal with his objections in a fair way.



His main objection is: that the Germans never would have retransmitted the actual time-base-signal-phase towards the ground station. They would either have locked it onto the regular EGON signal pulse electronically or, like was done in British GEE aircraft displays, having set or controlled its correct setting manually. 

He seemingly hasn't noticed all the many encountered critical timing problems.




Summarising what his objections are:


His first point cannot be waved away, they indeed where clever and have designed many sophisticated systems.

The second point is maybe a bit easier to counter:




Please remind, that the FuG25a receiver front-end is being constantly wobbled (as to guarantee that also off frequency signals can be captured), which is causing an amplitude modulation of the received signal. Or expressing it in a different way: this is causing additional side bands due to the rotation speed of the wobbling motor.



A screen shot from a received Nachtfee signal, thus a signal equivalent to what one may expect to receive from the Freya-EGON ground station at some distance; where the signal strength is still reasonable by the way. It is clearly visible what the implication of front-end wobbling is

Those having ever dealt with locking systems may wonder whether this blurry signal is providing solid and stable synchronisation. Especially in the context of 1940 techniques.



Another weak point is what should be the implication when they would have encountered the two following situations?



The red pulses are originating from the Freya-EGON signal pulses. The yellow one is from Nachtfee, when the 'order' pointer is set at Pauke (S) or eventually caused by operating the "Freya-Polwender" switch



What would happen with the synchronised time base system when both, the EGON reference- as well as the Nachtfee 'order' pulse are adjusted at 0 degrees? Isn't likely that the synchronising circuit may fail to distinguish what pulse should be locked (synchronised) upon? I have shifted both pulses a tiny bit as to make it visible what the difficulties may become


    So far we have dealt with Hans Jucker's perception of the Nachtfee system. There are, however, two major points which are neglected by him, and these are: why do they have implemented two system controls which doesn't have had any operational function?

Regarding Hans Jucker's point: that the Germans were then very clever designers, why should they have implemented these facilities without using them?


Whatever my objection against Hans Jucker's system concept is, two points he certainly has, this is questioning whether this system was a failure. As well as: was the system concept practically working over such a long distance (up to 250 km), where the actual FuG25a transmitter as well as receiver antenna (both combined) is rather short against the operated wavelengths? We might have to take into account, that Freya-EGON have been using the Freya Mattress-Antenna arrangement also for EGON operations. This would eventually have increased the antenna gain considerably. Consequently, its operational range.


In the course of this arguments, he suggested that the original time-base-reference-pulse should also have been derived from the Nachtfee console. Somewhere in my survey I have noticed this already, but there simply is no provision whatsoever. He suggested that this may have been sabotaged. Which is most unlikely, because this signal should have originated from a stage before the first "Phase" goniometer. As you may have noticed:



The regenerative divider principle used in the Nachtfee concept. The grid of the divider stage is very sensitive to interference. Sometimes even the high impedance loading of our scope probe is interrupting its proper functioning

It is apparent, that when an additional signal should be provided for a special purpose, that at least an additional (isolating) amplifier stages is necessary, which actually isn't the case. There simply is no facility existing!



Owing to the lack of final conclusive (technical) information, I have to rely on what is believed the most plausible means how the Nachfee system may have been operated. I will, of course, instantly change my Nachtfee circuit perception, as soon as a document is proving that Nachtfee worked in a different manner. Hence, my current Nachtfee concept is only true as long as there does not exist a real valid system concept. 


Having considered all this, one thing is still left open: does he or someone else have information that they do not share? I have learned from this tremendous complicated project - that everything is different than it in first instance looks like.


Another objection is, that thanks to the two statistical programs attached to our website, I am able watching often who is visiting it and recognising what their entering parameters are. I must admit however, that this is not always fully possible, but the two main objectors of our Nachtfee project are no longer amongst them for quite a very long time (at least for many months). Thus they do not take notice of all the many considerations before some conclusions is drawn. They most likely do not have an idea why I came to draw a particular conclusion. Or they simply don't want to deal with it, but objecting or criticising?  Simply: Quantité négligable?

Arthur O. Bauer


On 18 May 2012

As an off spin of this new page, I receiver a nice contribution from Günter Koenig, which is worth being integrally copied, as it clearly points what the implication is as to get the best possible means of synchronism between the Nachtfee time base as well as the aircraft internal time base 


Lieber Arthur, lieber Hans,

dieses Thema Kommandoübertragung mittels einer Phasenänderung setzt natürlich voraus wie wir alle wissen, dass beide Uhren (Oszillatoren) der zwei Zeitbasisgeneratoren (Boden/Bord) absolut synchron, d.h. mit absolut gleicher Frequenz schwingen. Wäre das gegeben, würde ein einmaliger Phasenabgleich genügen, um Phasensynchronität her zu stellen und fortan über Phasenänderungen Information übertragen zu können.

Natürlich ist klar, dass das Flugzeug sich bewegt und jede radiale Entfernungsänderung bei ca. 500 km/h Geschwindigkeit dann bedeutet, das die Phasenanzeige ca. 2,5 Minuten zum Durchlaufen eines Anzeigefeldes von 22,5° bzw. 125 µs sich verändert, was bedeutet, dass der Bediener am Boden diese Änderung stetig beobachten und korrigieren muss.

Abgesehen von diesen durch die Änderung der Entfernung sich ergebenden Phasenänderungen haben wir es natürlich mit dem weit aus größeren Effekt/Problem zu tun, dass die Frequenz beider Oszillatoren nicht absolut gleich ist, sondern neben einer Absolutabweichung natürlich zusätzlich einer gewissen Kurzzeitstabilität unterliegt. D.h. im praktischen Betrieb dreht die Phase alleine durch die Summe der Absolutabweichung plus/minus Kurzzeitstabilität mehr oder weniger weg.

Wenn wir jetzt die Frage stellen, wie groß darf denn nun die Absolutabweichung der Frequenz plus/minus der Kurzzeitstabilität sein, kommen wir, wenn wir mal annehmen der Fehler sollte nicht  gegenüber dem Geschwindigkeitseffekt zu sehr in Erscheinung treten, zu erstaunlich hohen Anforderungen an die Frequenzabsolutgenauigkeit, respektive Kurzzeitstabilität.

Eine kleine Rechnung zeigt es:

Annahme: Kurzzeitstabilität +/- Frequenzabweichung, nennen wir es Fehlerabweichung,  1  x 10 hoch Minus 6

Periodendauer 2ms, Fehlerabweichung 2ns pro Periode.

Bezogen auf ein Anzeigefeld von 22,5° bzw. 125µs bedeutet dies, dass das Feld alleine durch die Fehlerabweichung in 125 s durchlaufen wird! Das sind dann auch etwas über 2 Minuten, also in der gleichen Größenordnung wie der Effekt durch die Änderung der Radialentfernung.

Wollen wir den Einfluss durch diesen Fehler der Kurzzeitstabilität +/- Frequenzabweichung weniger deutlich in der Phasenanzeige enthalten haben, muss diese Fehlerabweichung deutlich geringer werden!

Kurzzeitstabilität +/- Frequenzabweichung, also Fehlerabweichung 1 x 10 hoch Minus 7

Periodendauer 2ms, Fehlerabweichung 0,2ns pro Periode.

Bezogen auf ein Anzeigefeld von 22,5° bzw. 125µs bedeutet dies, dass das Feld alleine durch die Fehlerabweichung in  dann 1250s durchlaufen wird. Dies entspricht einer Zeit von ca. 20 Minuten!


Wir sehen an Hand dieser Rechnung, dass beide Uhren mit ausreichender Präzision auf der gleichen Frequenz schwingen müssen und die Kurzzeitstabilität des ebenfalls gering bleiben muss.

Die Rechnung zeigt, dass die Fehlerabweichung doch deutlich besser als 1 x 10 hoch Minus 6 sein muss, typisch wohl bei 5 x 10 hoch Minus 7 liegen sollte.

Der letzte Wert setzte zwingend voraus, dass beide Oszillatoren in einem Thermostaten betriebene Quarzosillatoren sein mussten, die zuvor durch sorgfältigen Abgleich auf gleiche Frequenz eingestellt werden mussten. Außerdem sollten beide Oszillatoren möglichst ununterbrochen und ständig geheizt betrieben werden. Die Bodenanlage war darauf durch getrennte Netzversorgung eingerichtet, die Bordanlage war mit großer Sicherheit so gestaltet, dass das Frequenzmodul eine Steckeinheit war, die zuvor am Boden ununterbrochen betrieben wurde und unmittelbar vor dem Einsatz in der Maschine eingebaut und praktisch ohne Unterbrechung weiter lief. 

Somit macht auch der mit 10 Quarzgeneratoren ausgestattete Bedienplatz Sinn, da dann entsprechend der als Pfadfinder eingesetzten Maschinen bis zu 10 Maschinen mit unterschiedlichen Quarzgeneratoren ausgestattet werden konnten.

Soweit hierzu meine Überlegungen.

Schönen Donnerstag (Christi Himmelfahrt),

Herzliche Grüße



Since August 2012


Please don't forget to use the handsome: Nachtfee Chronology page


And, the PowerPoint progress page (converted into PDF)


By: Arthur O. Bauer




Please go back to, or proceed with: FuG136-Nachtfee starting page! (Status: 5 March 2012)

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Please return to, or proceed with: Nachtfee survey page 3 (status: 21 December 2011)

Please return to, or proceed with for the survey pre-phase to: Nachtfee 3a (status 8/1/2012)

Please go back to, or proceed with: Nachtfee MLK Lab. Survey (status: 13 December 2011)

Please go back to, or proceed with: Nachtfee-Inbetriebnahme (status: 5 March 2012)

Please go back to, or proceed with: Nachtfee evaluation and conclusion page (status: 1 March 2012)

Please continue or proceed with: Nachtfee-FuG25a concideration page (status: 10 March 2012)

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