EZ 6 direction finder receiver.

 Direction finder receiver EZ 6

“EMPFANGER ZIELFLUG”

Overall description of the receiver as a direction finder.

This is a receiver, part of the Geman “PEIL G 6″ aircraft installation called  “Peil Gerat 6″.

It was used for navigation/directionfinding purposes in large aircrafts like the Heinkel HE 111, Junker 88 and so on. It was common for EZ6, to be combined with the Fug 10, where it would have b

een placed instead of the E10L receiver. This was called the Fug10P (Peil).

There are 3  frequency bands: 150 -300 Kc, 300-600 Kc and 600- 1200 Kc.

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Photo above: front of the receiver

  • Upper left knob: A2 is AM, Eich is calibrating the frequency, A1 is BFO is used by navigating, Bandbreite is making the MF smaller.
  • Upper right knob: Entrubing is cleaning the signal from “humm etc.”
  • Middle knob: tuning the frequency.
  • Lower left knob: gain controll.
  • Lower right knob: arrow is navigating by a double needle instrument type AFN2. Circle is “Rund Empfang, frequency band 300 -600 Kc. Communication purpose as a replacement band for the E10L.
  • Lower middle: connection for headphones (left) and test entrance for test meter PV10 for measuring the internal voltages.
  • Small upper right panel: Behind the trim pot for calibrating the frequency scale.

The inside of the EZ 6 receiver.

Note the text on the pictures for removal of the various part blocks and connections.

 EZ-6 003a

The front with cover panel removed.

EZ6b 012a

The block units from the receiver from behind.

EZ-6 010a

A connector of a unit.

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EZ6b 010

Here to be seen the contacts of band switch.

EZ-6 015

EZ-6 020a

EZa-6 001

Right the opened oscillator unit.

OSCb 001

Oscillator case with circuit removed.

OSC 001a

The removal of the oscillator ceramic plate. The green points are the data, where the wires, comming from behind the ceramiec plate, have to be desoldered.

OSC 004

The three wave band coils of the oscillator. Above in the picture, the metal cover of the coils.

OSCc

The three coils explained.

OSC 001b

The connections of the coils, the grid, anode and coupling coils. Very handy for measuring the coils.

Temperature compensation for to stabilise the frequency of the oscillator circuit of the EZ 6.

All the components of it are mounted on a ceramic plate as a printed circuit, which was very revolutionair  in that time, nowadays very common. This has a very good effect at changing wiring capacities, due to warming up of them. Also mechanically very stable to heavy shocks.

Other provisions were these ceramic condensers in parallel , which have a temperature coefficient control. When they get warmed up by the air in the small cases of equipment, their capacity values changed that way, that frequency stability of the oscillator is improved.

These special condensers, you can see in the picture above, the green and brown condenser blocks.

On the printed circuit plate of the oscillator ceramic plate in the left side of the picture above, you see these green and brown  condenser blocks. All ceramic  condensers, in parallel, are placed over the the inductancies  in the circuitry.

About these condenser blocks, there was another type with ceramic ones with different specifications . Different from these of the temperature coefficient types.

It is so special, that I like to tell something about it.

One is a special, great type of ceramic condenser, which proof the great knowledge of German engineers in that time. Consider, it is now more then 70 years ago!

These were made by the German manufacturer Hescho, who patented it, and made also the ceramic coils holders and variometers.

The ceramic condensers are very special made. In fact, they are very bad condensers with a big dielecric loss with a particular temperature coeficient.

The principle:

Let us look at the internal capacities between the anode and grid and between kathode and grid, eg.  Cga and Cgk,  of a radio valve. When the radio valve is warming up, and getting warmer and warmer, when it is delivering power, the anode dissipation is increasing, these capacities are changing, the value is getting higher. So the frequency of the oscillator is changing and getting lower. Characteristic curves and values are well known for each type  radio valve.

Now we look at these special ceramic condensers. When HF energy is applied on these condensers, by the energy of the oscillator,  the dielectric electric losses of it changes by heating up of his body, so the value of capacity getting lower.  Hescho managed to measure that amount of dielectic loss in these capacitors. so they could produce a large variety of different losses factors  in the capacitors very accurate.

 That is just what we need to compensate the frequency change, established by the warming up of the valve , so the anode, by the increasing anode dissipation. This proces is acting much faster, then the influence  of the temperature compensating material, in circomstances that the valve is switched off, so cooling down, and later switched on again. Consider, that the remainig heat in the cabinet of this valve is still reaching the temperature compensation material, while the valve has been already switced  off for a while.

So they made the curve of  these combination of condensors that way, by putting several of these condensers in the circuit, that it is compensating the changing valve curve. So frequency stability, needed in such circumstances in the airplanes, was increased well , especially in these oscillators. Note that the German equipment, especially transmitters, were not crystal controlled by lack of crystal material, which had to come from abroad and was of course not delivered almost in that war time.

But these condensers were probably only made for oscillators, not crystal controlled, of transmitters.

You can see this arrangement in the various transmitters for navy, the LO40K39, the MOPA transmitters of the FUG 10, S10K and S10L. Even, I saw it in the oscillator part of transceiver FU Sprech- f of the army. But these were probably only condensors with a temperature coefficient. In these MOPA transmitters of the FUG 10, this stabilsation method is most effective. The heat is much in the transmitter cabinets. The oscillator stage, a RL12P35, had to deliver much driving power, so getting very warm, by his big anode dissipation, for driving the power amplifier of 2 RL12P35’s, to let this amplifier provide 60 watts on CW. Below a picture of the condenserblock in a S10K transmitter. In my working FUG 10, the frequence stability is amazing, while the transmitter cabinets are pretty warm. The oscillator is of course not crystal controlled!

Kl-details-Lorenz-C5-Block-1-2Kl-details-Lorenz-C5-Block-unten-2

The condenser block of the S10K transmitter. At the right, a kind of printed circuit on the ceramic base.

I don’t think these condensers with that dielectrice loss were used in the EZ 6. Because it makes no sense. The oscillator in the EZ6 uses a low power valve, the RV12P2000. It delivers low energy to the mixer stage. So warming up of the anode is limited, so his internal capacities. But it might have been? I don’t know.

After the war, this manufacturing method of this special condensor was lost and forgetten. A synthisized module was used in oscillators. The frequency stability of them, depended on a crystal controlled reference oscillator. In fact a pity, but it worked well.

De EZ 6 as a direction finder.

fug002

Here the EZ6 receiver  as my “Peil G6″ installation. Just at the right above a controllunit. With the switch you can do an automatic DF ,with the amplifier V6 just below the EZ6 and you can do a DF by hand, using the big knob on it by turning it to the left (L) or to the right (R). The DF antenna will turn to the left or right .Also the speed of the motor can be tuned. Right below the rotarytransformer U11 for the powersupply. In the middle the DF instrument type AFN2. Just all above  the motordrive for turning the DF antenna. Also seen the sense antenna. The complete system is a homemade version, except for the PRE 6 motordrive.

hell-bernhard-Ysys-dev-indctr

The AFN 1 instrument. The vertical needle is pointing to the dot, when the airplane is at course. The horizontal needle is for the signal strenght of the beacon transmitter. Tuning at maximun signal of the receiver tuning.

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The DF antenna system. Above the sense antenna (homemade), below the PRE6 motor  drive unit.

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Bordfunk 008

The PRE 6 motor and drive unit above and the ferriet antenne, just below the sense antenna, which is homemade one, by lack of the original one, but works very well.

This whole installation (certainly not original) is setup by my own and in fully working condition. The receiver is fed by the U11a by 24 volts DC. You can find the correct direction by rotating the little ferriet antenne  and watching the AFN 1.

Posted in airforce, German directionfinder Peil G6, German_ar.

4 Comments

  1. I lived in South-East England near a hospital during the war and we were plagued with diathermy interference from it, strong enough to blot out the BBC both day and night.

    In July 1943 I saw a Dornier 217 fly low over the hospital, so I think that it could have used its EZ 6 radio direction finder to home in on these diathermy transmissions.

    Do you agree that this is possible? Is the EZ 6 sufficiently sensitive to do this from 10 km or more?

    I can telephone you with more information if you email me your number.

    I am researching this raid which killed 108 people and this appears to be an important point.

    Nick Watson 0041 21 800 4354
    Route de l’Isle 15
    Pampigny
    Switzerland

    • Hello Nick,

      It is difficult to make that conclusion.In wsartime many stories were told, which often seemed not to be true.
      But thinking it over, I think not. Why. I will give you my opinion below.

      That the diathermy in the hospital blot out the reception of the BBC braodcasting, did happen because of the nearby situation. The distance between them and the BBC receivers is probably quit less. A diathermy unit consists in fact of a kind of power oscillator, power so big, that it is sufficient for his purpose. Only the frequency of that oscillator (in that time about 27/30 Mhz) differ a lot from the the receivers at the BBC frequency (Medium wave band?). But that diathermy oscillator produces so much harmonic signals, noise etc. into the receivers at the BBC frequency. But I think only at short distance, so in the close neighbourhood of the hospital/ hospital aeria. At a distance of a few miles, the interference has gone.
      The frequency in use by the EZ6 is medium wave, long wave. The diathermy unit has a frequency of about 27 – 30 Mhz (VHF). So totally different. So homing in into the the mainfrequency of the unit is not possible. Maybe in principle they could homing in to the interference, but that is most uncommon. They might use the horizontal needle of the AFN2 instrument to measure the strenght of that interferance. But the direction of it, it is not possible because of the principle of the system of homing. Homing in, they receiver needs a constant signal/carrier. Interference is just noise.

      Maybe there is a possibility homing in to the interference, by listening by headphones. By changing the direction of the lope antenna of the EZ6, you could determine the direction of the interference. But that is quit theoretical. The EZ6 receiver is a much, much better receiver then a common broadcast receiver! The plane had to be to close to the interference source. When picked up, there was no time anymore to homing in.In a few seconds it flew away from the target.
      But nevertheless, I do not think, the Germans used that method homing in to the interference of diathermy.

      But maybe people are mislead by another story about that diathermy units.
      The British RAF used the diathermy units from the hospital, by changing their frequency to the German aircraft blindbombing systems in aircrafts (see also the discription on my website, FuBl 2) to mislead them The refurbished diathermy unit was placed at the coastal line and created another “Lorenzbeam” A Lorenzbeam is in fact a small bundled radio signal, going forward to one direction, consisting of 3 other small bundled radio signals. One for “dots”, one for the Egui”signal and one for the “Stroke”signal. See discription in the post FuBl 2

      Now, in most cases the German plane picked up that signal and followed it. He never met the second original “lorenbeam” and lost in that way the target to fly in. So decided to go back to his base. But before he went home, he just dropped his bombs just somewhere. This often on villages,towns or maybe also hospitals. It was to dangerous to take his bombs back home. That did cost many lives.

      Maybe that Dornier plane was flying over your hospital because of that reason? And dropped his bombs accidently in your neighbourhood? He liked get lost of them as soon as possible, not looking, were to drop them.

      Conclusion:
      I do not think, the German planes with a EZ6 direction finder receiver, were homing in to that interference.
      Also the EZ6 was a part of a most common direction finder, placed in most German planes.

      Regards Peter.

  2. Peter,
    The museum only have diathermy accessories, but I have found on the web:
    1. In 1957 the hospital advertised a large diathermy machine, spark gap type, called a Penetrotherm,
    made in 1039 by Sanitas in Berlin. This is probably the machine used during the war.
    2. Another reference says that spark gap type diathermy machines operated between 500 kHz and 2 Mhz. Just right for the EZ6 to home in on..
    3. The 1954 1954 FCC annual report says a spark gap type diathermy machine heard in Oregon, Washington, California and many other states was traced to a doctor’s office in Miami, Florida.

    If you look at where bombs fell during this raid and then look at what they missed rather than what they hit, it would appear that this was a small daylight raid against targets that needed visual identification and which represented a menace for KG2’s main activity of night bombing. Among these possible targets were:
    ·Mullard Mitcham making valves for radar – missed by 2km.
    ·Creed Croydon making teleprinters and encryption equipment – missed by 100m
    ·E K Cole in Southend making night-fighter radar sets – too much cloud but an old lady killed by our AA fire.
    ·The Meacon (false radio beacon) at Flimwell near Tunbridge Wells – not transmitting.

    Could the EZ6 home in on such a broadband signal? Are you in contact with any Luftwaffe radio operators?
    A KG2 pilot told me that a camera took a picture every time a bomb was released, but he flew later in the war.
    The German reoprt on the raid talks about “QBMZ-PEILUNG UND KOPFFELNAVIGATION” Do you know what this is?

    Best wishes, Nick.

  3. Hi,
    I noticed there were two versions of EZ6. One with panel light for dial scale as in this set and the other is without panel light.
    Which version comes first.
    This EZ6 and the FUG series of receivers are very interesting.
    Eddy

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