FuBl 3F

Survey

Page initiated on 5 May 2017

Although, this project started on already January 2017

 

On 1 June 2018

contribution:

 + K + L + M + N + O + P + R + S + Ta + Ua + V + W +X

Y + Yb(including YouTube)

 

 

 

This project should be regarded Hans’ project

 

 

Hans Goulooze was concentrating first on making the remote control to the Ebl 3F operational

This didn't commenced well in first instance, because the parts obtained via Ebay weren't of sound quality.

 

 

It soon proved that quite some was lacking, such a the driving motor within the right-hand section of our Ebl 3F

 

On the right-hand side the FBG2 rmote control unit, which includes an indication that inside the Ebl 3F the correct setting being accomplished.

 

 

On 20 April 2017

Hans Goulooze was busy with getting sufficient sensitive reception.

 

With some care the EBL 3F started to operate, albeit, in the beginning quite some work laid ahead

YouTube films demonstrating the FBG 2 remote control interacting with the Ebl 3F mechanism

Film 0233

Film 0234

Film 0235

Film 0236

Film 0237   

Film 0238

 

(C)

On 8/10 June 2017

 

Hans Goulooze has made good progress in getting the combined EBL3F and EBL2 operational again.

The previous week he encountered all sorts of nuisances, but didn't yet grasped what the faults caused.

 

 

On the left-hand side the EBL 3F receiver, next to it the EBL 2 module, with removed screening plates. In the centre Hans Goulooze holds an open AFN 1 indicator in his hands

For this occasion we operate an AFN1 because this sample is at hand including cable connector as well as neon indicator lamp.

 

 

Getting a better vision on what Hans is actually doing

Please notice the device with connecting-pin-holes. It is a very versatile device by which means one can measure signals inside a cable interconnection.

Its type is P Mst1 (Prüfmeßstecker Typ 1)

 

 

The centre connector-section is feeding the connector pins 1 : 1 onto the according test (Büchsen) connections of the remote P Mst 1 module

The pin and cable numbers are maintained equal. Albeit, that in one occasion a resistor being implemented; its purpose is to allow measuring across the resistor as to get the actual current flowing.

 

 

For this occasion the SMS signal generator being used as to supply the modulated carrier at 32.0000 MHz, which equals EBL 3F channel number 21

As to get 1150 Hz necessary for simulating the long-distance landing-beacon-signal an external tone generator being used.

 

 

It finally was discovered that an incorrect contact number inside the EBL 2 connector had been once made

This easily can happen as all cables are of equal yellow colour.

 

 

However, the fault was determined and it all started to operate as may be expected in this experimental stage

The small circuit between the coaxial antenna input and the coaxial cable interconnecting the SMS has been implemented as to prevent damaging of the SMS signal-attenuator.

 

YouTube films:

Film 0244

Film 0245

Film 0246

 

 

(D)

To be continued on 15/22+26 June 2017

 

Hans Goulooze continued with considering the means with which the EBL2 module can be interconnected onto the dipole matching box DAG1* ; the way this once had been done was accomplished by means of so-called twin-ax of bi-ax cable.

* DAG 1 stood for: Dipolanschlussgerät (type number) 1. It has to be noticed, that we have to make a - replica like - DAG device, albeit electrically of equal properties.

The EBL2 and DAG 1 combination being meant for receiving the 38 MHz landing beacon signals (700 Hz and 1700? Hz). Please consider in the next drawing the VEZ and HEZ signals. Such kind of beacon signals crossed the virtual landing path, informing the pilot that first he is 1000 m ahead of the the landing strip and with HEZ that only 300 m being left.

 

 

This drawing originates from my CHiDE presentation on Navigational Aids, of, when I remember well, 1997

It shows what the "Funk-Blind-Landefunkfeur" is about.

Before the war the so-called Lorenz Blind-Landing-System was used nearly everywhere in the civilised world. 

Please notice, that when the pilot reaches the main warning signal 300 m in front of the landing strip his altitude (h) should have been reduced to 30 m above ground level.

 

 

Although, not yet dealt with in great detail, it is worth noticing what the system was about; because sooner or later we have to deal with its aspects

 

An aircraft approaching from distance will likely receive the airport beacon signal (some even from > 100 km), telling the pilot that he is whether, just on the exact approaching path - hearing in his earphones an uninterrupted tone of 1150 Hz; or right of the virtual path receiving dashes and left of it getting 1150 Hz dots in his earphones.

The trick was - that when both alternating antenna patterns coincide in its virtual centre, that the pilot receives both complementary signals which is then recognised as a constant tone. The course meter (AFN 1 or AFN 2) pointing  (staying) in the centre between L and R.  In case the aircraft tends to become off the virtual navigational track the signal is becoming modulated with dots or dashes; the way it sounds telling him whether being off to the left or right hand path side.

 

However,

I bore in mind that about thirty years ago I obtained a bunch of German antenna cables. In our cable storage we indeed found where looking for, a special brown cable type. Its brown colour indicated that its application once was designated for the purposes where frequent cable-bending occurs.

For example, the early Würzburg type fit with its strange, soon obsolete, IFF facility. The two antenna-dipoles were mounted inside the parabolic mirror; left and right of the antenna arrangement. When the Würzburg antenna-mirror changed elevation  cables need to cope with (some) bending.  

 

 

Preparing the cable is more or less done in the usual manner

The main dielectric is most likely of the low-loss Opanol type, well suitable for its purpose. It isn't really solid but it behaves like foam. Foam implies air-inclusions, which is increasing the so-called velocity-factor of the RF cable parameters; I guess ours ≥ 0.7  and also improving cable flexibility. Regular coaxial cables have a velocities of, say, 0.66

A brief tour through some aspects of speed of light (c) versus the signal velocity in systems consisting of dielectrics

More technical approach: v/c wave velocity through a medium versus speed of light;  and v = 1/ε 

However, copper antenna-wires hanging in free air are still being considered having 5 % velocity loss. An example, designing a dipole antenna for the 20 m amateur band (14 MHz); its λ = 21.428 m.

This antenna should therefore have a mechanical dipole length 21.428 : 2= 10.714 m

Considering 5% wire velocity loss is reducing the antenna wire length to: 10.714 - 0.5357 = 10.178 m (considering that the central feeding points are very near to one another).

Let us now consider we would like to use our brown cable as to constitute a ¼ λ stub. I considered our cable type is having a v = 0.7. The length of our imaginary stub would become then: (21.428 : 4) ∙ 0.7 = 3.749 m.

The consequences of all this, is, that signals travelling in a cable or transmission system is doing so never with the speed of light - but with a considerable lower velocity. The less dielectric constant (ε) involved the more a transmission line reaches the speed of light; but will never attain it. How light behaves in fibre optics I don't know, but it is most likely that these also have to deal with velocity reduction owing to dielectrics.

 

 

Maybe recognisable: around the two conductors being wounded a 'silver like' tape (the phenomenon is not well visible on our photos)

This silver-like shining isn't like that but might originate from 'surface light refraction', as this tape proves to be fully transparent.

 

 

Maybe this photo helps you to understand what it all is about

It is astonishing that this cable remains over more than 70 rather flexible. German coaxial or related cables where of a rather high quality standard. Maybe, rather expensive too, as, for example, the copper screening breath is rather heavy; hence, production consuming quite some Cu quantities.

It has to be noticed though, that in those days they may not have operated this more expensive (brown) cable type between the EBL 2 and the AAG1, but the less flexible 'blue colour' cable type. However, we only possess of it a short sample of not yet, say, 70 cm length; hence, for our display purpose too short.

I suppose: that the application of tape surrounding both copper conductors is to create flexibility between the foam-like cable dielectric and the (two) cable conductors.

 

 

Maybe this presentation is more recognisable

 

 

Just before soldering

Time and again it proves, that decisions made some 30 to 40 years ago are later often decisive for (new) projects. Gathering bits and piece, where the direct purpose wasn't always understood, but the 'trust' that it might later fulfils a purpose.

 

 

Hans Goulooze has started considering as to how it later can be mounted on display, of course, fitting within the designated display space

 

 

Viewing it slightly different

 

Hans Goulooze's first idea is constructing a light wooden frame so that we can learn how it all fits together well; with the aim later creating metal mountings. 

 

 

The space where the FuBL consisting of an EBl3-F and EBl2 + U8 is planned to be positioned is just between the border of the glass-window and the (white) wall below the two blue-window- frames

It is evident that space is quite restricted, but with some care it should be makeable.

The 'Funktisch' has been pulled towards us, as to show what it actually is about; but regularly it is to be noticed through the glass-window.

 

 

The FBG2 (the device with the number scale) is to be mounted within the previous shown genuine 'Funktisch' left of the Morse-key; this was its wartime placed within the Siebel type 204 aircraft

This aircraft type was used for carrying passengers on quite long distances (I guess up to 8, excluding the crew); and it flew still in post war days, in several countries; I know in Holland and Switzerland, but likely in more countries.  

The FBG2 is the electrical remote-control of the blind-landing receiver type EBL 3-F.

 

For those interested in the FuBL system its genuine manual might be helpful. Also increasing understanding of what we actually are doing.  

 

D.(Luft) T.4058: Funklandegerät Fu Bl 2, Geräte Handbuch Februar 1943 (please notice that its data content surpasses 12 MB)  This data has kindly been made available in digital format with courtesy of Ernst Wagner, Kemnath, Germany.

 

(E)

On 8 September 2017

Summertime has apparently passed, albeit not yet according the regular calendar.

 

In the meantime Hans Goulooze has done a superb job, he created a wonderful wooden frame which just fits within the board-display-space available.

Please notice first the second foregoing photo.

 

 

Our consideration first was how to integrate the FuBl 3F - Ebl2 installation in to the already existing display space

The locks (Schlösser) should arrive, Deo volente, Saturday 16th, this month; Hans is desperately waiting for them.

 

 

Invisible on the rear side a common 'ground rail' being implemented (please notice the next photo the Al strip at the rear side of the wooden panel

 

 

 Hans has used cable colours as far as possible according the genuine cable data, but where we couldn't match to this, he used other colours but consequently

He also has drawn a wonderful sound cable-plan accompanied with full details.

Please notice, just visible the Al guarding (ground) rail.

The switch-handle is for selecting the two possible power modes.

 

 

Hans provided, a facility with which we have a choice between operating the alternator U 8 (Umformer type 8) or allowing operating it via regular external power supplies. These supplies are to be interconnected onto the terminals: BA (24 V) and A (260 V)

 

 

The coloured wires are well visible

We are happy that we just have enough complete sets of plugs and according cable connectors; as these nowadays are most difficult to find.

 

 

These quite odd connector types genuinely originate from pre-war days; but have been used as long as design originated from pre-war or very early war period

It should be noticed that Blind-landing gear existed already since the later 1930s, and accordingly systems were implemented in GAF service.

However, technology improved and systems have been modified step-for-step. Therefore it was quite logic that when implementing single modules into an existing rig that, for simplicity, the original connectors types were still utilised.

 

(L)

On 15 September 2017

Hans Goulooze continued yesterday with 'his' FuBl2 - EBl3F project.

 

 

Hans' wooden - combined EBl 2 - EBl3F - being placed, temporarily, where it ultimately should be brought on display

When brought to a conclusion it should: constituting an integral part of our aircraft wireless rig. 

 

 

Viewing for a bit different perspective

The remote control at the glass-window is finally to be implemented in the genuine Siebel 204 wireless/navigation table.

However, we encountered a problem concerning the output signal of the EBl.2 module; the signal often drops 10 or more dbs.

 

 

For this reason the EBl 2 module had to be taken out-of the wooden frame

Please notice that the so-called locks should, Deo volente, be collected on the 16th in Driebergen.

 

Hans's first action was to look for supply voltage faults

Knocking at various points on the EBl 2 chassis resulted in a wild response on the oscilloscope. Those familiar with those kinds of annoying faults, will not wonder that after all plates had been removed the failures couldn't be reproduced!

But,

we also know - that this doesn't mean that the faults have been solved!

 

 

My proposal: let us wait until the next week

Thinking the encountered effects over again, it might be caused somewhere within the VEZ or HEZ signal filters. The latter consisting of an 1150 Hz modulated tone for this occasion.

Albeit it, that we haven't yet implemented the landing-beacon functions (@ 38 MHz), but instead of modulating the EBl3F signal with 1150 Hz. Because both systems join a common audio channel.

 

(M)

On 21/22 September 2017

We just received another Ebl 2 module: 

 

 

After having demounted the front-cover-panel it was discovered that this device is in a rather sound shape and most likely - inside - untouched

We have been informed before we obtained it, that the so-called Kabelschänze being cut off, but  substitutes are accompanied.

 

 

Photographed from a different perspective

It is noticed why the cables had been cut, as the cable insulation deteriorated; considering the forgoing photos this module might originate from the end of the 1930s or early 1940s. Whether this is the reason for insulation deterioration I cannot say. My suggestion to Hans Goulooze: let us operate it first in this genuine fashion.

 

 

 What might occur is that some capacitors will fail in due course

On the far left-hand side the notice the 38 MHz VHF front-end section.

 

 

Schloss type Fl 28251 (Fl was a GAF part designation); 'opened' 

 

 

Locked

Aren't these wonderful replica's?

 

 

He did a really wonderful job!

 

 

Preliminary checking how the Schlösser should be mounted

 

 

This lock had to turned as to ease lock-access

 

(N)

On 18 October 2017

Some progress has been made with respect to replacing the wiring of the two EBl 2 connection cables; one for the supply the second one for interconnecting signal cabling.

 

 

It is well visible that Hans does his work meticulously! 

 

 

Viewing it from a slightly different perspective

 

 

(O)

On 19/20 October 2017

 

Hans Goulooze has accomplished renewing the so-called Kabelschwänze (the cables between the EBl 2 module onto the connectors.

 

 

After some queries, likely caused due to confusion, all started to respond appropriately 

 

 

Viewing at it slightly from a different perspective

 

But Hans has built also a beautiful substitute antenna, which normally was built just inside the belly of the fuselage; as not to much causing drag, but still receiving the two beacon signals at 38 MHz un hampered.

Isn't it really wonderful?

 

It electrically should be fully operational; as the measures are copied from the genuine manual

Even the height above the metal plain is kept according the data in the manual.

 

We possess genuine German twinax-cable (bi-ax) and Hans has already calculated the values of the antenna matching substitute module. Both - his calculations - as well as the data given in the manual are about equal.

Our idea is, to build the matching unit into a box that should be mounted near to the antenna feeding point, but at the rear side of his antenna rig. Albeit, such that optimal tuning can be accomplished conveniently.

 

 

In my vision this is the optimal place to mount it at the wall (just up of the central heating tubes)

We have also discussed it being mounted on the sealing, but in my perception people have inconveniently looking straight upwards.

 

 

Looking again at this beautifully made construction It looks like that this FuBl 2 test set isn't operational, but it fully is.

 

 

It has been opened because the antenna current meter isn't responding, but likely the meter or the thermocouple is defect

This test set generates most relevant landing beacon signals including the VEZ and HEZ signals; please notice the yellow text "Modulation".

 

(P)

On 16/21 November 2017

 

In the meantime Hans has, with great ingenuity, adapted the sockets of neon indicator lamps (glass bulbs), as the one used first wasn't suitable for an application within the EBL2 marker-beacon circuit indicator (38 MHz marker signals) (mounted within the AFN 1 or AFN 2 instrument).

I wasn't aware that it is, in many cases, possible to separate a glass-envelope from a lamp base by means of simply using a hot-air-blower set for at at least 300 C°.

With some care and suitable tools, as well as precautions concerning the high temperatures involved, it isn't a too difficult job.

A range of types have been tested, one was found more or less suitable, but it just not yet performed perfectly.

The reason was found on the web, where special neon indicators were on offer. These wore a red colour ring on its glass surface. Hans could order, luckily, a few samples. The GAF Fl. stock-number clearly indicates that it concerned a special performing indicator type.

Our commitments and results on these aspects were nevertheless worth it.

 

In the course of our neon indicator survey we experimented with matching appropriate bias voltage, where ignition should take place only as a result of the demodulated marker beacon signal content

Please notice the neon indicator bulb a bit up during experiments.

Also was noticed, confirming an old GE publication, that neon lamp cathodes are sensible to external light approaching the cathodes.

 

 

No comments

When we have to observe the behaviour of Marker beacon signals, at least we should possess a test generator tuned at 38 MHz and modulated with the appropriate beacon-tone signal.

 

 

But after seriously testing, it we found some faults, among it a defect antenna-current-meter (0-50 mA)

Secondly, a more serious problem, the 35.2 MHz quartz oscillator stage isn't functioning.

But why?

We went back to the LMK lab and tested it on our Saunders rig. Its R1 was about 50 Ω. Please notice these quartz types are oscillating at their fundamental mode!

Only Carl Zeiss Jena, the famous optical and fine mechanical company could manage the task!

The implications have to be investigated in due course.

A disadvantage, we possess the schematic of a PSU-A but our apparatus carries type PSU-B. We already encountered quite some differences.

Hans did a search on internet, and time and again he landed on our website!

Also in the 35.2 MHz oscillator stage.

Which should become a special project or call it survey to be reported upon.

 

Hans has already dismantled it, as he removed the moving-coil meter section, because apparently the thermocouple is defect, as is so often the case.

 

 

The thermocouple device is just within the 'Mipolam' frame construction

In my perception a bit crude.

Our test generator was designed by Lorenz, but manufactured at a Philips factory somewhere in Eindhoven.

 

 

Formerly we couldn't see where the thermocouple had its actual defect, but now it appears that just at the thermocouple junction one thermocouple wire is detached (broken off)

 

 

Maximum meter deflection

Getting a feeling what the actual current sensitivity of the moving-coil meter is.

 

 

Not yet minimum scale deflection

We do not possess a thermocouple for 50 mA HF, but Hans possesses a Philips TH 2 type fit for 15 mA. For our preliminary experiments it should do.

 

Maybe a bit bulky compared to the 'Mipolam' type frame. But we have found room outside the moving-coil meter.

What counts first is short wiring onto the HF source, onto the meter is dc current fed only.

 

 

Our meter is now nearly ready for mounting it into its meter-housing again

We tested it by means of a dc current and 40 mA reading equals the TH2 thermocouple maximum current load.

 

(R)

  On 30/11 and 3/12 2017 we continued   

 

Please notice the neon indicator on top of the AFN 1 Blind-landing moving-coil indicator

EBl 2 marker beacon receiver input being fed by means of a: BALUN (Balance- unbalance) device.

 

 

We encountered a curious phenomenon, when the neon indicator ignites the sound pitch changes considerable accompanied with strong sound distortion

The tone just represents equals what being generated via the signal generator.

But:

 

Please watch the additional distortion

In our perception: The neon-indicator is loading the circuitry, but by its own means it is starting to load-and-unloading; causing an additional signal frequency. This is what being noticed.

When we look a bit down at the CRT screen, we still recognise a quite sound sine wave, but with a strange signal form.

In earlier days, there existed tone generators relying just on this technology (effect), providing audio signals; but not sinusoidal like.

 

 

Having just changed the setting and feeding at a lower signal level onto the regenerative 38 MHz landing beacon receiver, within the Ebl 2

 

 

Hans Goulooze could obtain some of the special indicator bulbs

The red ring indicating that it concerns a special selected type, just fitting for its purpose. The criteria: igniting voltage - cutting-off behaviour; a red dot (not visible) on the bajonet socket indicates the way it should be mounted. As it does matter onto which electrode is fed plus or the minus voltage.

 

YouTube Films

Film 249    (267) Showing the AFN 1 neon indicator driven by the Ebl 2. Viewing and listening to the mean beacon signal (1700 Hz); warning that the landing=strip is 300 metres ahead. Notice, that in practice the 1700 Hz signal being interrupted at a high rate; as to enhance the attention of the pilot.

Film 250    (268) Listening and showing AFN 1 pre-warning the pilot that the landing-strip is 3000 m ahead. Signal interrupted less frequently.

 

(S)

On 27 December 2017

Hans Goulooze has started with provisions to install the 38 MHz, landing beacon antenna reconstruction.

For it, it is necessary to create an electrical substitute for the antenna matching unit. Also providing two small Al mounting frames for fitting it onto a wall. 

 

 

Hans works always meticulously

The frame turned upside-down.

 

 

Viewing the 38 MHz antenna-tuner substitute, because a genuine one is lacking

The tuner in- and outputs are both symmetrical.

Luckily we possess genuine German screened symmetrical cable; sometimes known as: biax or twinax. 

Fortunately, the manual is providing the coil winding measures.

 

 

 It looks sound, isn't it?

 

 

Hans is removing the cable insulation

Its construction is most elaborate. Its brown colour indicates, that this cable type being meant for flexible operations.

Notice, that the 'Opanol' insulation (dielectric) should not stick together with the (quite heavy) copper core due to adherence; as the cable structure could otherwise become faulty.

For it, double tapes being wound in counter-spin, around each of the two copper cores. Due to this technique, there exist flexibility between the quite heavy cable dielectric (Opanol) and the Cu cores; allowing some amount of bending.

 

 

When you look carefully, you might recognise the two 'counter-wound' tapes structures

The Al-shining is resulting from light refraction, because separated tape strips look quite transparent.

Cu might have been a strategical material though, the Germans allowed lavish application of Cu in cable industry.

 

(T)

On 4/8 January 2018

 

Hans continued with approaching the faulty trimmers and thereafter with getting his Blind-Landing-Beacon antenna mounted onto the wall.

 

Hans, from his professional background in 'process quality-management', possesses a sound understanding of the behaviour of various materials.

 

Let us follow his line of approaching the repair of our defect trimmers.

 

 

When I arrived in our Klooster premises last Thursday morning, Hans had already removed the oxide at the silvered trimmer disk; by means of a heavy version of "Scotch Brite", as to allow proper soldering

Please bear always in mind: that one should never approach these kinds of (silver deposited) defect trimmers with a solder type containing lead (Pb)!

The proper way is using a mixture of silver-tin.

We luckily possess a bobbin of silver-tin solder; albeit purchased about 45 years ago.

I have repaired trimmers with this solder decades ago, these weren't always looking nice, but fulfilled my requirements.

Hans came up with a crucial suggestion: that during soldering 'the trimmer body' should be brought up to a temperature level slightly lower than the solder-melting-point.

These kind of "hot-air pistols" can be bought nowadays in nearly every tool shop or market.

However, for it, you need at least some assistance.

 

 

  Before approaching the delicate trimmers, we used another sample, showing a similar defect

 

 

Please look carefully, you might notice what our current problem is

Just the failing solder contact between the silvered trimmer-disk and the contact-screw.

 

 

The actual defect shown more in detail

 

 

It is clear that we have created a sound contact between the trimmer disk and the spindle-screw

Don't worry about the brown residue - because this originates from the necessary solder-flux one has to employ. Which can simply be removed by means of, for example, alcohol.

Our advise, be careful, that the flux residue does not enter the space between the trimmer disk and the fixed trimmer body.

Therefore, we turned the trimmer such that the flux residue washes easily away. Even renewing the alcohol liquid ones or twice, is advisable.

 

 

Finally we approached the defect trimmer belonging to our Schwabenland receiver survey project

Again: don't worry the brown residue, like the foregoing trimmer, originates from the necessary solder-flux.

Our silver-tin solder does not possess a flux-core, therefore a substitute flux has to be attached before starting the soldering process.

Later on we built the latter device into its Schwabenland coil box again and it responded as what may be hoped for.

 

The first trimmer we did repair, belonged to the antenna matching box to the 38 MHz main Blind-Landing-Beacon system.

 

Now time is right for attaching Hans' 38 MHz beacon antenna arrangement onto the wall. Our criterion: best placed for demonstrations.

 

 

 

First, Hans had to measure where the screw-holes should placed

 

 

Hans really did a great job

The construction allows still tuning of the antenna matching unit; mounted at the rear side of the antenna substitute.

 

 

Without comments

 

 

We should be careful with mounting the biax-cable onto the wall

In particular in regard to the central heating tubes, of which one might become, sometimes, quite hot.

 

(Ta)

On 11 January 2018

Hans encountered strange instable EBl2 responses on 38 MHz.

 

 

It appeared that the concerning NF 2 valves suffered from defect metal screening

 

The date concerning week 34 of the year 1938, noticed on the metal valve-screen might also indicated the age of our EBl2 device, which internally proves to be virtually untouched.

 

(U)

On 12/13 + 14/17 February 2018

 

The interruption of about a month, has been caused mainly due to quite annoying troubles encountered within concept of our PSU0-B test set; meant for the EBL2 and EBl3F beacon receivers.

 

We encountered:- that the 35.2 MHz quartz oscillator stage was generating, but not at its appropriate frequency; often between 130 and 160 MHz. Even not directly related to an according overtone mode.

 

The difficulty encountered, was that the genuine REN 904 valve, actually operating far beyond specs, oscillated spontaneously.  Even in the case of heavy capacitive loading of the valve anode.

 

The actual circuitry differed from what being mentioned in the available manual.

 

 

This circuit we found actually existing in our test set, apparently genuinely manufactured this way

This schematic differs fundamentally from what is shown in the genuine PSU0-A manual.

This circuit oscillates between, say, 130 and 160 MHz; or it doesn't oscillate at all.

However, during our long lasting experiments, I understood that apparently the function of the trimmer, was not adjusting frequency, but was more-or-less adjusting the signal feedback.

 

 

 

In an attempt to restore the circumstances as shown in the real manual, we reconstructed it this way; equalling what the genuine manual provided

Do not wonder, that nothing fundamentally has changed in the response of our oscillator circuitry.

A range of signals discovered, but in no way at the quartz frequency spectrum of 35.2 MHz.

Could it be that our quartz crystal is defect? I don't believe so, because some time ago we tested it on a professional quartz parameter test set.

 

 

This circuit didn't change the mall-functioning of the circuit

 

In a desperate mood I decided to continue experiments in our MLK lab.

 

 

It is evident, that the wartime Carl Zeiss Jena quartz still resonates in its 'series mode' vibration on 35.203877 MHz

 

 

Measuring its so-called R1 value of 43.5 Ω

Constituting the series resonance resistance; a tuned circuit in resonance responses (obeys), principally pure ohmic.

Interesting, the optimal vibration frequency can be determined by watching the R1 value versus tuned frequency. There will be find a minimal resistance value somewhere on the digital reading; in our case, this being 43.5 Ω.

I suppose not too bad, for a fundamental quartz resonating on 35.2 MHz. Even nowadays, fundamental resonance at 35 MHz is a great exception. One would use an overtone circuitry.

I first used the same setup as being used in the Klooster premises, thus experimenting with a REN 904 valve again.

The annoying results being equal as was encountered in the Klooster previously.

My first thoughts went in the direction of phase-delay due to this odd valve type. After all, it most likely originated from the long metal rods (Stege) carrying the electrode system, within the valve envelope; because oscillation continued even when the REN 904 anode was blocked with capacitors of 15 nF and beyond!

Maybe not in accordance with wartime technology, I took ultimately an ECC 81 valve. Fortunately, in the valve box was also found an according noval socket.

 

The circuit responded well, but again at about 129 MHz and beyond. 

 

 

My next move was restoring what was given in the genuine manual

 

Before I started the circuit experiments with the ECC 81, instead of the quartz crystal, I injected a 35.2 MHz signal from our R&S SMH generator and tuned the output trimmer for maximum signal output.

 

 

HT was again provided, and it started to run at the so desperately wanted 35.2 MHz

The grey valve envelope belongs to the REN 904 valve used in the forgoing (failing) experiments.

 

 

It is clear that the circuit operates

 

 

As to save the counter input circuit, I use the 10 x probe attenuator cable for the counter

Reading off: 35.21150 MHz.

A Pierce oscillator type does necessitate a complex tuning (loading) in its anode (collector/drain) circuitry.

Let us notice:- a Pierce oscillator circuit operates in the so-called parallel resonance mode. Parallel resonance-mode lays always a tiny bit higher in frequency. Quartz in parallel resonance allows some frequency adjustment, in contrast to series-resonance mode. 

Don't tune the circuit at maximum output, it will next time not starting up automatically. What should be done:- is finding a proper point on the slope of the tuning curve. I luckily remembered this aspect from my commercial production of VHF/UHF RX in the 1970s. Albeit using transistors, but the principles do obey equally.

 

 

Only a scenery

 

 

Wednesday all should be cleaned and then preparing for transport

 

I have discussed with Hans Goulooze, this afternoon, that we should try to implement an acorn valve type 4675 made by Philips. Its advantage, it necessitates 4 V filament which equals the provision for the availabl for the REN 904.

The application of an ECC 81 would mean, that a voltage doubler arrangement has to be implemented as to make 4 V → (about)  8 V

However, its slope factor of 2 mA/V is quite lower than 5 mA/V for an ECC 81.

An advantage of adopting an ECC 81, is, that the output level (second triode section) can favourably match onto the "loading" conditions of the REN 904 mixer stage.

We will see whether it can be made operating.

 My temporair opinion:-

It might once have been, that the criteria were:-  a particular REN 904 valve sample and a selected 35.2 MHz quartz module allowed proper operation, otherwise, the adopted circuitry could never have operated reliable.

It has to be noticed though, our current quartz crystal is not the one once matched onto the moment of its acceptance.

Why?

Donald Prins, once employed at the Philips Quartz Crystal plant, had it laying at his desk (he wanted testing its parameters). He reported - that due to its cylindrical shape it rolled off his desk and smashed on the ground, the remains weren't useable anymore.

Luckily, at a meeting (Dresden 2012), I saw our current quartz device inserted in an old 1920s set, where it apparently wasn't meant for. I told the owner my particular concern and he very kind gave it to me.

A question should be razed, why have they adopted such delicate circuity?

In my perception, they only gained the lacking coil-body.

Though, was this all worth it?

I tend to understand - it was not worth it! 

Gaining perhaps 1 RM lower material/production cost versus likely much higher costing efforts as to match (unreliably) valve and according quartz crystal devices.

 

On the 14th the MLK lab table has been reshuffled, the necessary 35.2 MHz modified oscillator circuit and other bits and pieces being prepared for transport to the Klooster premises again. 

 

 

Quite a different situation than the foregoing scene!

 

 

Don't you agree?  

 

(V)

On  1/5 March 2018

 

Continuing the foregoing experiments - it first seemed to perform well, but at a sudden moment the 35.2MHz quartz failed resonating entirely.

Is it really defect?

Therefore, I went back to our MLK lab; tested it, and found that the equivalent series-resonance R1 parameter being 40.3 Ω. Which proves, that it is still functioning.

After some consideration, I drew the conclusion, that mechanical overloading could have caused this nuisance.

Why not adopting a transistor stage instead?

A long time ago, I designed and manufactured VHF and UHF receivers (1970 early 1980s). Therefore we used for some circuits BF494 and BF495 transistors. A brief check showed, that some are still in stock in our MLK lab. I know - not the most up-to-date types, but according their specs these must do well on 35 MHz.

First I considered the same type of oscillator as was used within the valve driven oscillator; a Miller type circuit.

This didn't work.

My next approach, wiring it like in a Colpitt-oscillator circuit; where the crystal (resonating in parallel resonance) being wired between base and collector (in valve terms g1 and anode).

This worked instantly fine.

It proved, unexpedly, that some reactive component in the collector load should exist. Hence, tuning the tuned circuit a bit on the slope instead of at maximum amplitude. It proved to be necessary to adopt a symmetric load against ground. Always bearing in mind, that stable starting-up and operation is our main aim.

This became true, when I switched it on on the next day (2 March) no signal could be detected. A slight change in setting the tuning trimmer (the big ceramic disk) and it did start operating again; but just at a tiny bit lower signal level; caused by the slight detuning. When aligning the circuit I apparently forgot this very fact.

 

Quite basic isn't it?

I operated it first at 12 V dc, but the current was considered too high. Watching the current meter - I reduced the supply voltage and found 8 V a still sound functioning oscillator and measured 17 mA; implying a power consumption of 136 mW. Say, about 50% of wherefore the transistor had been designed. 

After tests for several days, the open wire construction was put carefully in a box and brought to our Klooster premises.

My first action was to implement it into the existing facilities in the PSU0-B test set.

 

 

This photo has been taken afterwards, thus when it all pointed into the way it should be accomplished (the red wire supplies the +8V)

Just underneath the quartz socket we just see the: flying-wire technique mounted BF494.

I adopted the already existing tuned circuit, including using the genuine ceramic trimmer (the big circular disk)

After quite confusing experiments, it eventually was found that an ECC 81 can perform as was expected (but not more than that) and it was checked whether the genuine REN 904F valve, originally used, would perform too.

And it astonishingly did perform about equally. 

 

 

Albeit, I kept a cathode resistors as was already adopted for the ECC 81.

Why?

Because I still used in the foregoing experiments the genuine valve base of the REN 904F; it being simple pulling out the ECC 81 "Ersatz" valve and inserting the genuine valve REN 904 instead.

Because it proved favourable to operate with a self-contained bias I implemented a 470 Ω cathode resistor blocked by means 15 nF; I measured across it, say, 2 V.

I kept this provision for the REN 904. Short circuiting the provision didn't influence the measure output amplitude much, but is found better for the life of the >75 years old valve sample. 

Keeping the genuine situation as much as possible genuine.

 

 

The red clamp is supplying the 8 V for the transistor stage

It proved, however, necessary to the implement an additional tuned circuit in the anode of the driver-buffer stage; fed from the existing HT within the PSU0-B set.

By this means it became possible to separate completely the the mixer-valve grid from the buffer stage.

 

 

 

Quite a strange experience, tuning the buffer anode circuit, had to be accomplished by looking just for the point where the sine-wave shown on the oscilloscope screen is looking sound

Up or down this point the projected sine-wave looked a bit distorted, proving the appropriate functioning of the tuned anode circuit.

 

 

Also the counter showed stable performance

 

 

For it we even re-adopted the genuine Philips type anode resistor again

The circuit now used is in some respect on the lines of the genuine PSU0-A manual which we have to rely upon.

On the far left-hand side the flying small tubular capacitor is only 1.5 pF whilst in our test set genuinely a 100 pF capacitor had once been implemented.

But our test set type could never have functioned reliable!

In some way or another, once a tuned circuit coil must have been mounted.

But where?

 

 

A way should now be found to implement somewhere a miniature transformer 230 - 10 à 12V

The Philips type trimmer has been mounted a bit facing downwards, as to prevent it touching the metal case or box. Please notice it operationally carries about + 200 V against ground!

Its expected power consumption may be considered for, say, 30 à 40 mA due to the additional 7808 regulator consumption.

 

Final comment today: what looks promising, is the fact that the oscillator signal watched on the oscilloscope (output of its output) is steady, in contrast to the foregoing situation, where always a sudden irregular signal amplitude being noticed.

Further tests should proof whether this presumption is valid.

 

(W)

On 2 April 2018

Progress have been made in getting the PSU0-B test set operational again albeit, in a some modified fashion.

A sound tip I got from Raymond Domp-Frank, and Hans Goulooze obtained a sample for us.

 

 

Considering the size of the ½ W resistor (or the 0.1 inch separated holes) - this module is compact and and provides 15 V; even up to 5 W

Why using a big resistor?

The reason is quite pragmatic, we had no smaller type at hand.

The application of a 100 Ω resistor is that we can smooth the operational voltage a bit from the quite steep pulse slopes on the module output. One never should load pulsed power supplies directly with a 'too big' smoothing capacitor. Improvement was got using several capacitors types wired in parallel.

100 Ω has been chosen also as to ease reading off the voltage but mA. Hence, 1.5 V equals 15 mA current flow. 

 

 

These two photos showing the two point at which the 230 V can be found, necessary for feeding our switched mini power-supply unit

The two connections in between (the middle) might once have been meant for 110 V operation.

 

 

Space was easily found to mount the small 15 V power supply

 

 

The new 35.2 MHz quartz oscillator stage being fed from this new power-supply module (just visible on the other side of the Al plate

Please do remember, that we had been forced to modify the 35.2 MHz quartz controlled oscillator stage for several reasons. In the concept once provided, it oscillated on roughly 140 MHz or 160 MHz, but never on 35.2 MHz!

My first modification was changing the circuitry as originally given within the PSU0-A manual (Pierce type cicuit).

Result: negative.

Then creating an adapter as to adopt one side of an ECC81 valve, but using a base as genuinely used for the REN 904F valve. This operated well, but at a certain instant it stopped operating.

It proved - that apparently the 35.2 MHz quartz did strike due to overloading!

In a desperate move, I considered adopting a low power transistor controlled stage.

This proved to be a sound option. As to amplify signal and still using the genuine REN 904F valve, it finally started working reliably. Albeit, that additional modifications had to be implemented.

There are still enough PSU0-A/B sets around elsewhere, that this modification being worth implementing. 

 

 

Looking at the antenna-output of the test set

Don't be surprised, the combined mixer and output stage is being supplied with three different signals:

 

The 35.2 MHz signal visible is e sine-wave ripple, the local oscillator given by the equation: Fx = Ft - 35.2 MHz.

Fx = the mixer signal frequency; Ft is the output or transmit signal; resulting from the mixing process.

For example when the test set should provide 33.33 MHz → 35.2 - 33.33 MHz = 1.87 MHz

For 30.00 MHz we get 35.2 - 30.00 MHz = 5.20 MHz 

For 38 MHz, the landing beacon marker: 38 - 35.2 = 2.8 MHz

The Germans call such signal: Überlagerer, elsewhere known as local-oscillator (LO).

And, very significant, we get to notice the audio modulation: 1150 Hz;  700 (VEZ or 1700 Hz (HEZ). It concerns anode modulation of the mixer stage.

Being aware of a single-tuned anode coil, we may expect that all signals in some way will be measurable at the antenna base.

Is this hampering the purpose of our test set?

Not really, because the DUT, in casu: EBL3F (or EBL3H) is possessing selectivity from its own right.  Maybe less within the EBl2 receiver front-end (audion).

 

 

Apparently another signal maybe 30.5 MHz

Maybe you can recognise the 35.2 MHz ripple super-imposed onto the summing output signal

 

 

Most likely the 38 MHz beacon signal und 700 Hz modulation

 

 

I suppose that that this signal concerns the 1700 HEZ* signal

* HEZ Haupteinflufzeichen, or main landing-beacon signal, received when the aircraft is 300 m in front of the landing strip.

 

 

Test set place in its genuine case

Please notice the 10x scope probe among the antenna 'substitute' antenna cable.

 

 

The arrows pointing at the fixing screws

 

 

(X)

On 14 May 2018

Hans Goulooze, whose project the FuBl rig is, has put on paper something fundamental, which cannot be found in the genuine manuals at our disposal. Namely: the way to calculated the main landing beacon channel numbers versus channel frequency; visible on the EBl 3F remote control, these channel numbers might be similarly used the tuning dial of a regular EBl 3H (Hand = manually tuned)  

He also explains briefly, as to how he did once change the tooth-cam disk for one obtained on Ebay.   (I have to apologise, for not having a more adequate description of this device)

 

Which is an essential part of the remote-control system, kept within the EBl 3F receiver module.

Let us please follow the line of his brief explanations:

 

Channel frequencies and alignment of the EBL3F receiver.

 

The EBL3F is tuned from the cockpit by the control unit FBG2. The tuning of the EBL3F is by a continues 3 fold variable capacitor, coupled to a motor driven mechanism. Under operational conditions, no fine tuning is required.

Only a few frequencies of the EBL3F receiver are available through documentation.. The manual (Ref.1) informs that the channel frequencies are regularly divided over the available range and quotes the following:

Channel   1:  30,000 MHz.

Channel 16:  31,500 MHz.

Channel 21:  32,000 MHz. Also the channel for frequency callibration on the platform with PQK-4.

Channel 32:  33,100 MHz.

For reproduction of the  total list, the following algorithm may be applied:

Channel frequency = (channel number -1) x100KHz +30,000 MHz.

The measured -over all channel accuracy- from a number of adjacent channels, may be considered as  plus and minus 10 KHz.

The measured bandwidth of the receiver is 100KHz (-10dB).

 

In addition to these observations the following has to be added.

The original drive unit attached to the receiver was unservicable and had to be replaced by  a “spare” unit.

 The drive unit is mechanicaly aligned to the receiver with dowels and pre drilled holes, assuring proper alignment of the clamp and the ceramic shaft of the tuning capacitor (Fig. X) .

The correct relative channel alignment is mechanically provided by the wheel with adjustable tabs (Rast und Nockenscheibe, Ref. 2). This wheel is directly coupled to the clamp. The slot in the large lever provides the reference locking point for the respective tabs on the wheel, after actuating the tuning procedure by the FBG2 (see Ref. 1)

At disassembling the drive unit and receiver, the spring loading of the double gear wheels, directly attached to the locking wheel, is released and has to be restored at assembly.

For the initial realignment of the tuning mechanism, this should be performed at channel 1 (30 MHz), at maximum of the tuning capacitance.  

The oscillator can be adjusted  at one channel only. It is assumed that this channel 16 or 32. The coupling of the tuning capacitor and the wheel has to be such that alignment of the oscillator, by the precision trimming capacitor accessable at the front of the receiver (Ref.3), is valid for all other channel frequencies.

After reviewing the hardware concerned  and having gone through the frequency alignment procedure, it may be assumed that the positioning of the tabs on the wheel has been performed with the aid of a mechanical template , rather than individual placing and locking. Therefore the drive unit may be considered as fully inter changeable.  

  

Ref. 1: D.(Luft) T 4058, Funklandegerät Fu Bl 2, page 29.

Ref. 2: D.(Luft) T 4058, Funklandegerät Fu Bl 2, page 61.

Ref. 3: D.(Luft) T 4058, Funklandegerät Fu Bl 2, Anlage 3, C50.

 

 

(Y)

On 28 May 2018

 

We have now reached a point where our project is beginning to materialise. The circuit has been built inside an Al die-cast box; though, still encountering some nuisances. One of the problems was that we expected a ß of a PNP transistor too optimistic. It was found that we had to look for a different solution. In a box we found an old type BD 238, having sufficient driving power for switching a miniature relay.

However the first results weren't convincing either. This proved to originate from the fact, that the basis current apparently was adjusted at a too high current level.

We also have been forced, to implement a 7812, because, for what ever reason, the small power module apparently delivered > 16 V, and this was damaging two NE 555s.  

 

 

After reduction we got a driving voltage on the miniature relay of about 10 V (leaving 2 V across the BD 238)

 

 

The board on the left, contains the timing and relays driving provisions; on the right the two timing relays for L-R switching

This photo had been taken before relay 3 was adopted.

Finally, the box should be closed and so screened-off electrically.

 

 

It wasn't easy to take this screen shot!

We are viewing at a switching behaviour within 1/8 s, but interrupted by the 7/8 s lasting switching sequence; as to get it right I had to take several photos. (Time-base expanded x10)

 

Our first trials could be set up.

 

 

Albeit, not yet everything being ready (the small green cable picks up the PSU0-B output signal); the 'PL' plug should hold the vertical antenna-rod

The generator set for 30.5 MHz

The outline of our set-up is already visible.

The black knob on top of the box box, is for manipulating the levels of the L - R signals; as well as the centre-signal where the according meter staying, slightly vibrating, at the indicator (AFN1 or AFN2) centre marker.    We can even proof that it is acoustically possible to adjust the L-R meter indicator just at its centre position, without looking at the scale of the indicator instrument!

Just where dots and dashes are fully complementary and constituting a constant tone of 1150 Hz.

 

Why all these efforts?

For it we have to explain first the Lorenz Blind-landing-system; once employed worldwide.

 

Why not considering first my Navigational Aids paper, once given for CHiDE at Bournemouth.

 

 

The upper drawing is showing the general outline of the "Anflugfunkfeuer" (AFF) system

Maybe confusing, but aircraft could approach an airfield (aerodrome) from a farther distance, think of 50 or even more km.

Our current guiding beacon (L-R) simulates a likely condition. Were a mere guidance equilibrium is reproduced; but also the situation of being far off the centre of the guiding beacon signal.

Please take some time for digesting the upper drawing.

 

The vertically radiated signals at 3 km and 300 m in front of the landing field - or strip, is to be dealt with a bit later (lower drawing).

The warning beacon signal had been picked up by means of an fixed antenna kept parallel onto the aircraft fuselage. As to prevent too much drag, it often had been kept within a provision just outside the main airflow.

  

Please bear in mind, that the system being meant, occasionally, to function as a more or less true Blind-landing gear. Let us focus first our attention onto the way the so-called A-N guidance beam being created.

The signal carrier was modulated with a 1150 Hz tone signal.

 

 

The energy source being the dipole placed in the centre

On the left- and right-hand side we notice two, what might be, dipoles.

The most common dipole type is constituting a ½ λ radiator. Though, we also see that the dipole centres being fit with a switching arrangement.

In case the switch being opened: we get 2 x ¼ λ radiators; these do not respond onto  ½ λ signals.

In other words, they do not re-radiate accordingly.

As soon as the reflector starts responding, it also reflects the signal.

Towards the centre - signal radiators, depending upon the measures of the construction, an field interaction will take place; in our case resulting in "forming" of the radiation pattern. And providing the advantage of allowing keying of the (directional) radiation of the two antenna-beam-pattern segments.

I hope you can grasp what happens.

 

I would like first to acknowledge Dieter Beikirch (Minden), who once showed me his wonderful collection in 2013, where he also could simulate the L-R guiding signal. How he accomplished it I have no idea.

 

However:

The left-hand beam-side being switched on-off within a sequence of 1/8 s (dots) and the right-hand side of the beam in sequent being switched on-off within 7/8 s (dashes). As to prevent confusion, please consider the upper drawing of the first Lorenz sheet.

 

 

This is Hans Goulooze's basic concept

The timing and relay drivers were created around a well-known NE555 integrated circuit.

The concept shown in the first two photos of this section Y.

The Lorenz system relied upon beacon signals between 30 MHz and 33,33 MHz (RX EBl. 3...).

However, the nearby approaching beacon signals were once standardised for 38 MHz (RX within the EBl. 2).

 

But how can we adapt our L-R simulator module for also cooping with the VEZ and HEZ signals on 38 MHz?

After brief considerations, we adopted a very simple modification:

 

 

 

 The main trick: relay 3, constitutes a relay with two conditions. We choose for: when the simulator being connected onto power, relay 3 being kept in a none-conducting state, but when power is off it will be in a conducting mode.

When power is off, the switching electronics is off anyway, and the two relays kept in the off mode. But the 38 MHz beacon signal (VEZ and HEZ) can now pass through the entire box straight away.

 

It has to be noticed though, that the pre- and main-marker signals also being switched on and off (but with regular intervals), but their only means being: as to alert the pilot of the significance of marker-beacon-signals; hence being at 3 km or 300 m in front of the landing strip. The existence of such signal is also noticed from a neon-indicator, integrated within the indicator instrument. 

 

 

The yellow coloured 38 MHz VEZ and HEZ text is good visible. Please look a bit left-hand side upwards, and you can see the switch selecting the VEZ (700 Hz)  and the main marker beacon HEZ (1700 Hz)

Maybe not the most attractive photo, but just showing what it is about. Might have been taken somewhere in early 2017. 

 

 

The mechanical sizes of the 38 MHz dipole construction is according the manual; the Al frame is adopted as to let it electrically behave like once did a genuine antenna

Please notice: in the background the Blind-landing indicator-instrument (just in between the EZ 6 frame and the EBl 2 and EBl 3F. You might even recognise that the meter pointer pointing at the equilibrium between L and R

 

(Yb)

On 1 June 2018

 

 

 

The simulator ready for trails

 

Youtube Film

Film 260 (276):    Today we can show the way our newly designed Blindlanding simulator device does operate. The L - R (left-right) indicator type AFN 1 is appropriately responding upon the long range beacon dot-and-dash signals. The dots are indicating that the aircraft is on the left off the virtual (landing) beacon centre; whilst dashes indicate off to the right of it.     When the aircraft system is just receiving L-R signals of equal strength an uninterrupted tone (1150 Hz) being noticed; and the indicator pointer stays just at its centre marker. This phenomenon can be accomplished entirely acoustically; so that a pilot did not need to read off the L-R indicator instrument permanently.     A dot constitutes a pulse length of 1/8s and the dash is lasting 7/8s;   7/8s +1/8s representing just one second.     In the days of the Lorenz Blind-landing system, timing was accomplished by means of mechanical switches, whereas we are relying on electronic circuits.

 

Next:

We would like to continue with approaching the EBl2 "Audion" front-end receiver, tuned at 38 MHz.

The problems we are currently facing, is the lack of sufficient information on as to how this quite delicate circuit once had been aligned. The manual we possess, simply noticed: that one should fly the aircraft and testing its adjustment yourself.

A complicating factor, inside the L-R indictor is the integrated neon indictor (especially selected type). When this device being ignited, the section starts to respond like a generator and causing a heavy audio distortion.             A neon device responds, like a zener-diode: when conditions are appropriate, causing oscillation (zener-diodes causing noise because switching is not being delayed due to ignition up to at least in the UHF spectrum); when the voltage across reaches the ignition point (in case of a neon controlled device) it ignites. But doing so, it will stabilise at a lower voltage level, when due to the flowing current the voltage drop is too much ignition might stop. Voltage is rising and the cycle starts to repeat again; when a capacitor is incorporated a saw-tooth signal component might occur. 

Such (light) indicator should warn the pilot that he is crossing one of the two pre-landing marker beacon signals (3 km or 300 m in front of the touch-down point). Hans Goulooze's idea, is, that he would like to adapt an additional BNC chassis connector, which automatically should provide the 38 MHz signal (when appropriate) onto a balun).

 

 

 

To be continued in due course

 

 

By Arthur O. Bauer

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