German FUG 10 airforce radio installation

FUG 10 means: Funk Gerät 10.

The Fug 10 is a very complex radio communicationsystem for communication  between airoplane to airoplane (Bord zu Bord) and from airoplane to ground (Bord zu Boden). It consists of several receivers and transmitters for the shortwave and long wave and a lot of remote controlls. In other circumstances it is combined with navigation purposes. (Peil G6 with EZ6 receiver, then called Fug 10 P).

The transmitters are very stable in frequency, by using special temperature compensating arangements  in the oscillator circuit. Consider, that this oscillator is not crystal controlled. The heat inside the cabinet is very high, because the principle is a MOPA transmitter in a very small cabinet. The oscillator valve is RL12P35, which much deliver much driving power to the power amplifier. This power amplifier has to deliver about 60 watts to the antenna at CW mode, by use of 2 RL12P35’s.

This arrangement was not only the use of ceramic material, but also a special condenser block in the circuit of the oscillator. Just see the picture above.

These condensers had a big dielectric loss with a particular temperature coefficient. More about this a extended explanation in the post EZ6 DIRECTION FINDER.

Displayed in the picture above my Fug 10 equipment. It is in working condion! I use the the short wave transmitter and receiver in the 80 meters amateur  band and made several contacts. The frequence stability is amazing!

Most units (EK,EL,SK FBG3, SchK13 and U10E ) are in working condition. Upper row “Funkerschaltkasten (switchbox), EK receiver  (shortwave 3-6 Mc), EL receiver (long wave 300-600 Kc). Mid row “Fernbediengerat” FBG3 (tuning the antenne tuners, switching antennes etc.), SK (shortwave transmitter), SL (longwave transmitter). Lower row “Eigenverstandigung Verstarker” RG 10 (intercom amplifier etc.) , “Umformer” U10 e (rotating power transformer for the receivers).At the back of the rack are placed, not visible on the picture,  the AAG2 antenna tuner and the transmitter  rotary transformer U10S.

The picture below an older version of my FUG 10.

On the left lower row, a important control unit, the FBG 3, explained later in the post. At the front 2 knobs for tuning the AAG for matching the antenna to the transmitters for long wave and short wave. One knob for long wave (blue) and the other for short wave (red) . This knob is mechanical attached to a synchro motor system. In the mid the antenna current meter. With the big switch, with scale, in the mid, you can switch the transmitters either for long wave are short wave and which antenna to be chosen. Normally one short  antenna f

or short wave, and a long antenna, the trailing antenna, for longwave. It is possible to change the long wave transmitter from trailing antenna to short antenna, so the short wave transmitter from the short one to the long one. This in case, one of the antennas is broken.

In the above picture you can see at the left de ADb ‘s (Anschluss Dose ). In this case a ADb13 type. It is a remote connectionbox for the microphone-telephones in the oxygencaps of the crew. At the right the U-10-e rotarytransformer for the receivers.

On this picture above,  you can see the trailing antenne  type AH-10. At the front of the “Funker Schalt Kasten” is a switch to move the antenna wire up or down. Also a indication meter is placed, for how far the trailing antenna is released.

The FUG 10 with the fully working AAG 3. Note that the trailing antenna is also there, which came later in the collection.

The vacuumrelay for the antenna.

The inside of the AAG. Left the vacuum relay. When pushing down the CW key, the relay comes up. When releasing, it falls down again after a few seconds. This is working very well and pleasant. Above the long wave variometer. Above the variometer, the indication scale of the tuned frequency, the same scale is on the FBG3 control. Both he scales are turning synchron with tuning.

Another view of the AAG. At the left, the short wave variometer to be seen. Just in the mid, the synchro -motor for driving the variometer coils. This motor is driving by a “Drehfeld  System” , a kind of electrical achs, coming from a same type of synchro in the FBG3. This synchro is turned by hand with a knob, with same scale as on the AAG, to tune the match.

Here the AAG on the testbank and wired up. To see if it is working. To the left the schematic of the manual. Lateron it is connected  to the FBG 3 at the FUG 10 display. And could be working from the FBG3 unit.

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Some time ago, I bought a fine looking German receiver, the R87E SADIR.

It is a VHF directionfinder receiver, frequency covering 66 – 120 Mhz.

A picture is shown below.

The receiver was made in occupied France by for instance SADIR-Carpenter located in Paris.

It was used by the Luftwaffe as a direction finder in the Y-Peiler system. To find the location of the bomber plane groups, flying over Europe to the the german cities and industrial factory location to destroy them.

The code name was FuSan A81bb1 or Pulm SK. SK means short wave.

But to increase the frequency coverage in order to receive more ennemy frequencies, there were several  receivers with different frequency coverage. And different code names.

See a list in the picture below.

With the aid of other Y-Peiler stations, the could find the location of the squadrons, in order to intercept them  by delivering the info to the airfields centers with the  fighter planes.

The system was very effective.

An example, the use of my receiver, the type E:

In most allied bombers and fighterplanes, there was a transmitter receiver, the SCR 522, with TR 5053 of 10-150 Mhz, and the British type TR 1143, 120 – 150 Mhz. onboard for communication. The trx were crystal controlled. It had 4 channels in this range.

This trx also had a socalled “pip-sqeepe ” channel. Periodically , this channel transmiitted a short signal.  With the aid of the signal, directionfinder station on airfields in The UK, could determine the position of the bombergroups in that way. See also in the post             for explanation.

So the SADIR receiver, R87E, with frequency coverage 66-120 Mhz was very suiutable to receive this signal from especially the American bombers and fighters to locate them (TR 5053).

Below some pictures of the SADIR receiver as a Y-Peiler.

Picture above the SADIR receiver in the radio hut as a Y-Peiler.

Above the radiohut of the Y-peiler.

Picture above another Y-Peiler station.

In the picture below, a situation of the Y-Peiler system, called  Y- Stellung,  in German.

Below some pictures of the inside of my SADIR receiver. Because it was made in France, they used American radiotubes in it. The acorn tubes 954 and 955. Also the 6K7, 6L7 and 6Q7.

So this SADIR receiver is a very interesting VHF receiver. With a great history.

Direction finder receiver EZ 6

“EMPFÄNGER 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 been 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.

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.

The front with cover panel removed.

The block units from the receiver from behind.

A connector of a unit.

Here to be seen the contacts of band switch.

To the right, the opened oscillator unit.

Oscillator case with pcb circuit removed.

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

desoldered.

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

The three coils explained.

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

Temperature compensation 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 all a different 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!

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. But all these condensers, in parrallel, did have a different particular temperature coeficient.

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.

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.

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

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

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.

Würzberg Riese transmitter SU 62 D of FuSE 62 D radar.

Würzberg radar is a German radar system from WW2,  to locate, mainly allied bomber convoys, on their way to targets in Germany. When located, their positions were given to the Nightfighters from a central command station, to intercept them. When they were in the neighbourhood the picked up the convoys on their own radar on board.

A lot of Würzberg radar systems were spread out over the occupied European countries, coastlines.

Their maximum range was 80 km and the working frequency was about 500 Mhz,  It even had a IFF system, called Gemse, for indicating weather the convoy or plane was enemy or freind. Its use was still in progress, when the allies made radar systems on 9,1 cm with better valves and more power, the magnetron. It took a long time, before the Germans were aware of this 9 cm radar. At the last end of the war, they developed also one, called “Berlin Gerat”. They came aware of it, after a bomber plane went down in the neighbourhood of Rotterdam, The Netherlands.

Also they could detect 9 cm radar pulses at that time, with a socalled “Korfu Empfanger”, so detecting these radar signals at 9,1 cm.

Because I am so interested in all kind of German radar in WW2, also allied ones,  I decided to publish a new post of this matter.

I have only some small parts of German radar in my collection, because it is most difficult, to collect some parts of these devices. They are very rare. But also valves for very high frequencies and magnetrons etc. are interesting.

After some visits to the museum of mr. Arthur Bauer of  The foundation of  German communication and related technologies  in Duivendrecht, The Netherlands, I had the possibility to examine his working Wurzberg radar installation. I must say, I was most impressed of it. Complete with transmitter, receiver, power supplies, units for measuring the  power and a signal  simulation unit,  called artificial target Rebock, to simulate a reflection target on the CRT.

Also the whole system is discribed in his beautiful and professional website.

Because I received some LS 180’s recently , the transmitter valve in this Wurzberg radar, I came to the idea to make a replica of the transmitter only, the type SU 62 D, belonging to the Wurzberg radar type FuSE 62 D.

Not having the idea, to let it will work once, there are so many other rare parts to be need. Just a replica, but it must be possible to let the heater glowing. Also the the length of the lecher lines are not right, but that does not matter, it does not need working.

This SU 62 D is a special one, because they could change its transmitting frequency some. The range was about 485 – 520 Mhz. This frequency change was sometimes a must,  because of possible interference with allied transmitters.

The inside of the Wurzberg housing at the back of the telescope. Note that another transmitter receiver (the SU 62 in the picture)  is used, then the type , described in this post. The different transmitter receiver , also Eidechse SU 62 called, could operate at 2 frequencies, 560 en 540 Mhz. The visible A and B on the front indicate it. Furtheron you can see the Impuls generator IG 62, providing the gridblocking of the transmitter. The CRT on the front, a LB13/40 can indicate the controll pulses for the grid blocking signal of the transmitter.

Some below, you can see a original picture of a Würzberg Riese radar. you can see his size, comparing it with the person in front of it. The reflector dish a 6 meter.  in the focus center , some little dipoles are collecting all the reflected pulses, received by the dish. The dish could turn in the horizontal position, just as well in the vertical position.  On a cathode ray tube, a LB 13/40 you could read the distance to the target in 2 ranges, eg. 40 km or 80 km range.

Picture at CRT, a target on a distance of 18 km. Picture taken by Arthur Bauer, PA0AOB.

There are still some Würzberg’s left here in The Netherlands.  For instance one in the Liberation museum at Overloon,which is very complete, and one at the Planetron in Dwingeloo. Both are sadly suffering from weather influences, because they  are placed outside in the open air. If nothing is done, they are rusting away. That would be a pity.

Another, still existing Wurzberg in bad condition,  at Dwingeloo, the Netherlands at this moment, 8-10-2015, at the  former Planetron. Note, that the parabool reflector is not original, but copied after the war!

In the past, after the war, 2 Wurzberg Rieses were in use in Dwingeloo.

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The 2 Würzberg’s beside the Dwingeloo radio telescope in 1950. All broken down at the moment.

                   The Würzberg at the right (eastern side).

Würzberg in use after the war at Kootwijk. For radio asteronomie.

After the war , most of the Würzberg dishes  in The Netherlands, were used for observation the H2 gas radio signals at a wave lenght of 21 cm, coming from milk way star galaxies.

They made the first map of our milky way.

To get more details in observations then those made by  the Wurzberg’s, the 25 meter telescope was build in 1956. This leaded by Prof. C.A. Muller. With the Dwingeloo telescope they could make a picture, just seen from of our earth position, of our Galaxy in the Milky Way.  During some years after the new telescope was build, the left Würzberg ‘s were in use  for examinig the radiation of the sun. The Wurzberg in the  front moved in the 1980’ to the Wehr Museum in Munchen .The other also was already not there anymore. The Würzberg housing went to the Planetron, see picture.

Now back to Würzberg again:

Wurzberg Riese, original picture.

Transmitter valve,  type LS 180, in use in the radar transmitter of the Würzberg. The copper wires at the left are the heater connections for 5,8 -6,2 volt – 15 A.  The real voltage to be used, is written on the glass of the tube. At the right inside the anode.

Some documentation about the LS 180 transmitter valve:

Manufacturer Telefunken.

Maximum frequency 500 Mhz.

Type: UHF triode.

Output 8 KW pulsed power.

Input 12 – 16 KW pulsed power, air cooling.

Anode voltage 8,3 KV.

Grid blocking voltage 2,1 KV negative by 1,8 uS. Delivered by the Impuls Generator type IG 62 D.

Heater voltage 5,8 – 6,2 volts by 15 Ampere! Value written on the tube itselves.

I looked funny to me to make myself a copy of the transmitter part, type SU 62 D. See the result in the pictures below. It is made at true scale.

The front and above seen.In the mid if the picture the LS 180.

The front side. L21 is the output cupper strip, just above the anode inside the valve. Below left, the condenser  C6 and the 3 resistors in parrallel. Left a power resistor(15 A) for putting the heater value at correct voltage, written on the glass of the tube.

The condenser (0,05 uF) and the 3 resistors (16 kohm) in parrallel are in serie with the 8,3 KV anode line. They take care, that the anode only draw current, when the condenser is disloading, when the valve is not blocked by his negative grid voltage. When the grid of the transmitter valve is fully negative at 2,1 KV, the valve is blocked, the condenser is loaded again.  The anode gets no voltage the anode  is drawing a current!. The next episode, the negative voltage on the grid is disappearing, the condenser is disloading to the anode , the valve is drawing current. An episode further the whole cyclus is starting again. It is like a safety circuit for the valve, because when the negative voltage on the grid has been disappeared by malfunctioning , the valve draws only current via the 16 kohm resistor. Note that the current is DC not AC.  This will reduce his total input power. Even when it is dissipating this reduced power, other safety systems will work, so protecting the valve and probably exploding the transmitter unit.

On the right the resistor for the heater voltage, when heater voltage is applied, this wire wound resistor is a bit glowing (I got no other resistor), because of the current of 15 amper is flowing in it. But that will be not a  difficulty. Resistor will not burn away.

Just down the resistor, the supply connector for the heater voltage and the negative grid blocking voltage of 2,1 KV – 1,8 uS, coming from the puls generator type IG 62.

At the left of the casing, you see a small handel. With this handle you can tune the anode lecher and the cathode lecher at the same time to the right frequency, to be used.

The arrow warns you for the very high dangerous voltage. The red and the green stripe indicates, that the equipment was most secret.

The transmitter is working!!

But not really, only the heater is glowing.  An intensive light is there, all gets very warm too.

I used a voltage of  5, 8 volt by 15 ampere for the heater.

The cathode lecher line and tuning, also the heater connection. In the mid of the lecher  line the tuning arm. which is tuning the length of the lecher, by shortcut a part, the quarter wave lenght for that frequency is established.

The backside. The upperleft connector is used for the 8,3 KV. Also the connection cable (at the right) to the grid of the LS 180 is to bee seen.

The circuit of the SU 62 D. It is just a  “simple” power pulsed oscillator. You can see the grid and cathode lecher. Capacitor C2 is for the degree of coupling, to let the system oscillate. The output device of the transmitter is only a strip, which is positioned around the LS180, so coupled to the anode,  by inductance.

The original transmitter SU 62 D , a picture taken by Arthur Bauer, PA0AOB, from his transmitter unit. Mr. Arthur Bauer has a complete and working  Würzberg installation in his museum.

The replica is now on display in my radio shack.

German FUG 10 airforce radio installation

FUG 10 means: Funk Gerät 10.

The Fug 10 is a very complex installation for communication  between airoplane to airoplane (Bord zu Bord) and from airoplane to ground (Bord zu Boden). It consists of several receivers and transmitters for the shortwave and long wave and a lot of remote controlls. In other circumstances it is combined with navigation purposes. (Peil G6 with EZ6 receiver, then called Fug 10 P).

The transmitters are very stable in frequency, by using special temperature compensating arangements  in the oscillator circuit. Consider, that this oscillator is not crystal controlled. The heat inside the cabinet is very high, because the principle is a MOPA transmitter in a very small cabinet. The oscillator valve is RL12P35, which much deliver much driving power to the power amplifier. This power amplifier has to deliver about 60 watts to the antenna at CW mode, by use of 2 RL12P35’s.

This arrangement was not only the use of ceramic material, but also a special condenser block in the circuit of the oscillator. These condensers had a big dielectric loss with a particular temperature coefficient. More about this a extended explanation n the post EZ6 DIRECTION FINDER.

Displayed in the picture above my Fug 10 equipment. It is in working condion! I use the the short wave transmitter and receiver in the 80 meters amateur  band and made several contacts. The frequence stability is amazing!

Most units (EK,EL,SK FBG3, SchK13 and U10E ) are in working condition. Upper row “Funkerschaltkasten (switchbox), EK receiver  (shortwave 3-6 Mc), EL receiver (long wave 300-600 Kc). Mid row “Fernbediengerat” FBG3 (tuning the antenne tuners, switching antennes etc.), SK (shortwave transmitter), SL (longwave transmitter). Lower row “Eigenverstandigung Verstarker” RG 10 (intercom amplifier etc.) , “Umformer” U10 e (rotating power transformer for the receivers).At the back of the rack are placed, not visible on the picture,  the AAG2 antenna tuner and the transmitter  rotary transformer U10S.

Picture above: an older picture,  close-up of the units.

On the left lower row, a important control unit, the FBG 3, explained later in the post. At the front 2 knobs for tuning the AAG for matching the antenna to the transmitters for long wave and short wave. One knob for long wave (blue) and the other for short wave (red) . This knob is mechanical attached to a synchro motor system. In the mid the antenna current meter. With the big switch, with scale, in the mid, you can switch the transmitters either for long wave are short wave and which antenna to be chosen. Normally one short  antenna f

or short wave, and a long antenna, the trailing antenna, for longwave. It is possible to change the long wave transmitter from trailing antenna to short antenna, so the short wave transmitter from the short one to the long one. This in case, one of the antennas is broken.

In the above picture you can see at the left de ADb ‘s (Anschluss Dose ). In this case a ADb13 type. It is a remote connectionbox for the microphone-telephones in the oxygencaps of the crew. At the right the U-10-e rotarytransformer for the receivers.

On this picture above,  you can see the trailing antenne  type AH-10. At the front of the “Funker Schalt Kasten” is a switch to move the antenna wire up or down. Also a indication meter is placed, for how far the trailing antenna is released.

The FUG 10 with the fully working AAG 3. Note that the trailing antenna is also there, which came later in the collection.

The AAG on the testbank. Just to be seen, the schematic diagram and wire connections.

The inside of the AAG. Left the vacuum relay. When pushing down the CW key, the relay comes up. When releasing, it falls down again after a few seconds. This is working very well and pleasant. Above the long wave variometer. Above the variometer, the indication scale of the tuned frequency, the same scale is on the FBG3 control. Both he scales are turning synchron with tuning.

Another view of the AAG. At the left, the short wave variometer to be seen. Just in the mid, the synchro -motor for driving the variometer coils. This motor is driving by a “Drehfeld  System” , a kind of electrical achs, coming from a same type of synchro in the FBG3. This synchro is turned by hand with a knob, with same scale as on the AAG, to tune the match.

A nice look to the vacum antenna relay. It can be activated (transmit and receive) by 2 coils, seen on the picture.

Picture above the AAG on the testbank. All wired up to let it work. The schematic left from it Lateron it was connected original to FBG 3. To see in the display of my FUG 10.