YouTube 3


Status: 5 November 2012


The aim of this new test series is, to explain, in more detail, what is happening on the various hypothetical or simulated CRT screens of Nachtfee. The two CRTs (LB2 and HRP2/100/1,5(A) part of the Nachtfee console are, of course, genuine. As we do not possess an accompanied aircraft display of the FuG136 system it has to be simulated*. We have reached the point where it is possible to show all system interactions. Shown is also, for example, what the pointer or vector of some of the Nachtfee commands are. Their true vector or pointing angle should equal the pointer setting on the 'Nachtfee order compass'.

* There are clear signs that our Nachtfee apparatus carries serial number 5 and it might be the last one of the series. To what we know from literature, there only existed 5 hand-made systems; this may well be the last one, as many RV12P2000 valves carry acceptance stamps of late 1944. The ‘Jahre tar-roll-capacitors’ carry markings of April 1944. According R.V. Jones Nachtfee was being operated during the Baby-Blitz of early 1944. Trenkle informs us that it was also used in late 1944 for some very special operations.


Testfilm 25    Viewing the Nachtfee console control screen (LB2). Watching the signals which have been received by the IFF set FuG25a and which is, of course, as it is the aim of an IFF system, retransmitted towards the simulated Freya_EGON ground system. That it flashes is due to the fact that these kinds of signal are being codes individually; as to distinguish between other aircraft. The FuG25a is provided with two Morse-code-keys. For simplicity, I have cut the metal key such that it transmit on - off - on - off space .... The flashing pulses do originate from the simulated EGON system, which is having a different PRF. During these experiments I sometimes lower the off-set difference a bit, as to make its recognition possible.

Testfilm 26    Viewing the dual beam CR tube HRP2/100/1,5(A). The pulses in the centre above and under the time-base line has to be aligned such that both pulse becomes back-to-back. This does not yet tells you whether phase alignment is carried out at 0° or at 180° phase difference. The maybe visible flashing pulses originate from the simulated EGON signal, which is having a different PRF than used in the operational Nachtfee (not valid for channel Q5, because this is providing 500 Hz PRF as well). 


Testfilm 27    Viewing the simulated aircraft system display (FuG136).


Testfilm 28    Viewing like the previous film-strip the simulated aircraft display.


Testfilm 29    Explaining the various 'orders' or commands. Examples are give as to how it should have been presented on the wartime special displays. For practical reasons, I use Z-modulation, whereas it is most likely that during the war they have used a display type as is shown in testfilm 25. Notice to it also: Bladwijzer186


Testfilm 30    Viewing the same kind of conveying 'orders' or commands towards the aircraft, though, now returning via the FuG25a IFF towards the Nachtfee ground station. The display is the control screen of the LB2. According to what we actually know, both, the Nachtfee and the CRT display in the aircraft, should have been constituted by a LB2.


Testfilm 31    Viewing the alignment of the internal Nachtfee time-base with the received signal returning from the simulated aircraft system. 


Testfilm 32    Viewing the two Nachtfee control screens together with the Nachtfee 'order' or command compass. This time the time-base-phase-reference is being modulated not via the mixing circuit, described in the things to be done-1 page, though, keyed directly via Rö8; which connection have been made additionally by us. This may not have been done this way during wartime days, but all possible experiments have to be gone through.



Please also consider the previous YouTube test series 2

Please return to the: Nachtfee-things-done main page