German directionfinder Peil G6.

Direction finder receiver EZ 6


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.

 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.

EZ6b 002

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.


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!


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.


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.


Altimeter transmitter/receiver RT7-APN1.



 This altimeter is designed for measuring constantly the height of the aircraft above ground, terrain during flight. It is also suitable in conjunction with an Automatic Pilot System.

There are more principles of altitude measurements, but the APN-1

a  FM CW radar altimeter.

It is supplied with a double Range Indicator, type AYD 3. One for  till 400 ft and one for 4000 ft.  One ft is equal to 0,3048  meter.

So 400 ft is 1,2 km, 4000 ft is 12 km.


Also a Limit Range switch is provided,

type SA 1, to switch for the desired altitude of the aircraft.

When no Automatic Pilot is used, the  Limit Range switch can be used in conjunction with a Limit Indicator, consisting of 3 lamps, red, white and green. All these items are at the dasboard. When not using the Automatic Pilot, a dummy connector is put in the receptable connector at the front of the transmitter/receiver J-106. When not placed and still Automatic Pilot is connected to this receptable by a cable, the change over switch on the Automatic Pilot box must be set on manual. When switched to automatic, these lamps have different functions.

In my installation that dummy is placed and the functions of the lamps are discribed just below.

At the Limit Range switch , the height of the aircraft , which is chosen to fly, or providing a flight with save height, can be chosen with the knob on it. When now the red lamp in the Limit indicator, is lightened, the aircraft is flying beneath the value on the Limit Range switch. When white, the height is about the desired value. When green, the height is above the value of the Limit range switch, so save height. See also the first picture below.

The principle of working is different from the SCR 718. See below the block diagram of the APN-1 Altimeter.




Inter connection diagram picture.


The APN- 1 is a frequency modulated  CW Altimeter. It , just like the SCR 718, determines the time required for a radio wave to travel from aircraft to earth and return. A different method of time measurement is used , which depends on the observed difference in frequency between transmitted and received signal.


If frequency of a radio transmitter is changed rapidly at a constant rate (frequency modulation), the transmitter will change frequency in the time required for a radio wave emitted by it to travel to earth and return. The higher the aircraft, the longer the time required for a round trip and the greater the difference between the transmitter frequency and that of the reflected wave when it arrives at the aircraft. This frequency change is the proportional to the altitude of the aircraft.

If the rate at which the transmitter frequency carrier varies,  is known , e.g. FM modulation, and this  signal is also modulated at a rate of 120 cycles,  is CW modulation, his frequency is varied from his center frequency of 400 Mhz , between 420 and 460 Mhz at lower altitudes of a maximum range of 4000 ft,  the elapsed time corresponding to any observed frequency difference is then established. This frequency difference (elapsed time)  is converted, in an electronic  circuit, which delivers a proportional current to drive  a meter instrument, the Altitude Indicator.

The output of the transmitter is a FM modulated constant carrier of 0,1 watts, which is radiated from a small half wave dipole, located, often,  just under the wing of the aircraft. Each wing carries one dipole antenna, one for transmitting, one for receiving.


The principle of the altitude measurement in the APN-1 will be discribed in the following presentation  below.


Above the C is constant all the time, so  when T in increasing, H is increasing too.






Above: when T is increasing, rate of change carrier frequency  is stable,  the beat frequency is increasing.




Above means: FM modulation of 40 Mc, CW frequency , and  and velocity factor (300.000 km/sec) is stable, then the altitude is proportional to the beat frequency.



Above the principle block diagram of the APN-1.

Below some pictures of my APN-1 unit. Just click on the picture to get a bigger one.



My  Altimeter unit RT7 APN-1.

Below the transmitter/receiver. Above left the Altitude Indicator and Range Switch unit. In the mid the 3 lamps  of the Limit Indicator. Just below at that, the 2 dipole antennas.


Transmitter/receiver box. Just watch the inserted dummy connector at the left, when the Automatic Pilot is not in use.


Left the height indicator with 2 scales on it. Below the 3 lamps of the Limit Indicator.


One of the small halve wave dipole antenna.

Comparison of FM and Pulsed Altimeters.

They are designed for different purposes. For instance for bomber aircraft, flying at great altitude and for fighter planes flying often at lower altitude, for attacking objects at ground level. Fighter planes use often the FM units, while bomber planes use the pulsed altimeters.

The FM unit has a very small fixed error while the pulsed unit has negligible  percentage error. The FM unit is intended for better measurement  at low altitude, while the pulse unit is better at very high altitudes. Often you can see at pictures, taken in bombers, like B17 or B 29, the indicator unit of the SCR 718 , type I-152, is to be seen. See picture below.


Just right down to be seen the I-152 indicator at the Bombardier position in a B -29 aircraft.


Here to be seen in the background, the APN-1 transmitter/receiver, in a fighter plane.


In the week of the 28-th of march, 2018, I changed the instrument panel of the altimeter. First, I did not like after all , the antennas being mounted on it and second because if I put the antennas on a separate mounting, the demo of the altimeter went better.

Below the pictures.


The new instrument panel.


The transmitter antenna at 400 Mc.


The receiver antenna.


The red lamp is lighten, that is correct, because the needle of the altimeter indicator is above the installed value of 50 ft at the limit switch.


 The back side of the panel. Note the rare connectors at the instruments.

The demo is going very well, if you move the receiving antenna. The indicator meter and the lamps are responding very quickly. This is correct, because at the functioning of the altimeter  at ground level  is always very unstable.  At bigger altitudes it is more stable.

transm 3

Replica Wurzberg radar transmitter SU 62 D.

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

Wurzberg 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 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 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 Wurzberg 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 Wurzberg’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.

Wurzberg Dwingeloo

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

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


The 2 Würzberg’s beside the Dwingeloo telescope


                   The Würzberg to the right (eastern one).

Schotels Dwingeloo a1958

A very beautiful picture  taken of  Wurzberg’s , in use in the past, and the new build 25 meter telescope , at Dwingeloo, The Netherlands in 1956.


Würzberg in use after the war at Kootwijk.

After the war , most of the Wurzberg 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. 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 Wurzberg again:

Wurzberg foto

Wurzberg Riese, original picture.



LS 180

Transmitter valves, 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.  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 made myself a copy of the transmitter part, type SU 62 D. See pictures below. It is at true scale.

transmitter 1

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

transmitter 2

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.

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.

transm 320150920_192928

The transmitter is working!!

But not really, only the heater is glowing.  A hell of light is there, all gets very warm too.

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

kathode side

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 coupled with the anode inside, through the glass, by inductance.

WB-rep-Urechse-TX-separat HT cable 8 KV HT cable -2,1 KV a

The original transmitter SU 62 D , a picture taken by Arthur Bauer, PA0AOB from his transmitter unit during experiment to let it work.

A complete Bendix radio directionfinder installation

Radio compass reciever

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  1. Radio compass receivers from Bendix.

Radio compass receivers from Bendix.

This directonfinder receiver  MN 26 is in fully working condition. Also functioning as a communication receiver in cinjumction with the TA 12 transmitter, just seen a bit on the right of the picture.

A complete Bendix radio directionfinder installation

Here the MN 26 radiocompass and controll boxes.

On the picture the next items;

MT51-C remote control for the Transmitter TA12-B.

MR9 frequency control box for the RA 10 DB receiver.

MN28-LB control box for the MN 26 receiver.

Directionfinder loop antenna MN20-E.

DF Receiver R10-DB.

Transmitter T12-B.


The Ra 10 DB  DF receiver above, the MN 26 -E below in the picture.


The Azimuth controller , indicating the direction of the beacon transmitter, piled up by the compass receiver MN 26. The pile up is done by turning the controller by a bowdenkabel.

TA 12 front 2

Transmitter TA 12, with 4 frequency bands, one for longwave and 3 for shortwave. The funny thing is that each frequency band (four bands) has it’s own VFO and only one poweramplifier, but again 4 output tuning filters with variometer inductance, to match it to the antenna. It delivers about 40 – 50 Watts on phone and CW. In the mid the earial current meter. For an output impedance of 50 ohm, it will hardley give a current of course.

The four knobs at the left are the channel preselector tunings, for each wave band one. Left of the knobs are the channelnumbers you preselected. In the mid under you can see the knob for preselecting one of the four wave bands.

At the right are the four knobs for tuning, by variometer inductance, the output filters for matching the transmitter to the antenna, depending which waveband and channel you choose.


I use a separate modulator, homemade, with 2 valves 807 in the final. It is doing very well. Also a mains powersupply is used.

 TA 12 upper

The upper view of the transmitter.

The box at the right is the VFO compartment. At the left upper, one of the four variometer inductances, four each band one.

TA12 relay

View at the power amplifier with relay for switching the antenna and HT to the amplifier. The 2 tubes are in parallel.

TA 12 under

The under view of the transmitter. The motor for automatic channel switching at the left is missing. At the right, the VFO box again.

TA12 side

Side view with the four tubes of the seperate VFO parts. Each frequency band  has it’s own VFO part, so also it’s own tube. Left up the power input connector.



The direction finder SCR 269.


The remote controll box of the SCR 269.


Aircraft receiving equipment type RA1-B.

This receiver is a real old fashion general coverage receiver. Alle the wave bands are close after each other, when turning the wave band knob. When turning and  reaching the end of the last waveband, you start again with the beginning of the first.

It was used for communication purpose, but also for direction finding. It is a wartime receiver. But also used after the war by the dutch KLM.  It is a real nice, sensitive receiver, pretty stable in frequency at CW/SSB, only  a bit broad medium frequency stage of  1, 6 Mhz. But receiving SSB signal is pretty possible, if the band is not to busy with other stations.


 Bendix RA1-B.


This is the Remote Controlbox of the RA1. Type MR-1B, in the condition I found it. The AVC on/off switch, the volume control is missing.


Bowden cables RA 1

Here the 2 original bowden cables for remote controlling the MR-1B.

When I obtained this remote control, together with a RA-1J, it  appeared to be a postwar (?) revision belonging to that  RA-J. The RA1-J was a revised postwar (?) one, because it had an extra mode swtitch on it’s front. Three positions: CW, VOICE and RANGE. This switch was also located at. the front of the  MR-1B. Watch also the missing switch : AVC on/off. The both potentiometers inside  were removed.

I decided to modify it into an original MR-1B, suitable for my original wartime receiver RA-1B.

Does anyone knows, which manufacturer it was, who carried out that revision?  Also what year, and in what aircraft is was being used.

I’m most grateful for more information. Pse let me know in the comment at the end of this post.



Finally the restaurated ware time MR-1B. When the function switch at the front of the receiver is set at “remote”, all the facillities are available on the MR1-B. Like band switching, frequency control, CW oscillator on/off, AVC on/off, audio and volume control.

At the right of the box, you can see the connector and cable to the remote entrance on the receiver.

RA1-B with powersupply

The RA1-B receiver at this moment,  with mains powersupply, by lack of the original rotary transformer , stowed away on a shelve, far away of it’s remote controll. Watch the connector with cable at the right to the remote control MR-1B.

“Pip Squeak” American/British

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  1. Contactor BC 608

Contactor BC 608


Although a contactor is often explained as a kind of IFF device in several publications on internet, this is not true. A contactor, even if it is British or American, is actually a device for determining the position of an aircraft. It has nothing to do with identifying if an aircraft is a “friend” or “enemy”. (IFF).

This signal was also called “PIP-SQUEAK” signal.

It is a mechanical clock device with an electrical  contact, which switches on a communication transmitter for 14 seconds every minute at a special frequency channel. The direction finder stations home determine then by a cross sense the position of the aircraft.

This contactor is often used in the SCR 522 VHF transmitter/receiver.

The British types are used in fighterpanes, like spitfire, hurricane. A big part of the south-west coast of the British empire was divided in sectors. Each sector had his own airfields with fighterplanes. When a german attack was expected , radar (home chain) determined the location and direction of the ennemy planes. A certain sector was activated then. The fighterplanes of that sector went in the air to be lead to the ennemy. The direction finder stations of that sector (about 2 of them) could determine the position of their fighters by the “Pip-Squeak” signal caused by the contactor transmitter switch on. So by radio contact the could give eventually coarse corrections etc.




This picture above is a contactor, type BC 608: an American product. There have also been British types manufactured, for use in fighter planes.

  • The switch on the left is used to activate or deactive the so called PIP-SQUEAK signal.
  • The switch on the right is used to activate or deactivate the clockwork of the BC 608.
  • The knob in the middle is to rewind the clockwork.
  • The quarter section as seen in the upper right in the display represents the 14 seconds read-off timer.



British version PIP-SQUEAK.

The purpose is the same as that one mentioned before. It has been used a lot in the BATTLE of BRITAIN during WW2. The contactor was switching on the transmitter , at a special frequency being not a communication channel, during equal intervals for some seconds. So the monitoring control centres knew exactly the position of  the fighter planes by piling them up. If known, they directed the fighters to the locations of the ennemy bombers on their way to Britain,  by another radio channel. The locations of the ennemy bombers were detected by the HOME CHAIN radar stations along the coast line.

Pip squeak was an very effective way, leading the fighters to their targets.


Here the Brittisch version of the contactor, mentioned before. It’s a type no 4. Cover of the right box has been removed.

Left the remote contactor, which switches on the transmitter, often a TR9- D used in fighterplanes like the Spitfire.

At the right the maincontactor. It is a mechanical clock, which steps forward the internal remote contactor relay. Can be seen by moving of the needle on the front. In the mechanical clock assembly, there is  a heaterelement  installed for maximum stability. In the middle of it a key, for winding up the clock.

On the front of the remote contactor, there is that red part, which stands for 14 seconds. The whole scale is 1 minute. So the transmitter is switched on every 14 seconds of 1 minute.

I have tested it on a seperate transmitter, and it workes very well.

The remote contactor has been place on the right of the pilot seat, the master is placed behind the pilot seat.



On the picture above, the same. Only the cover has been replaced. This has to be done because of the temparature stabilisation internally, which was for my test not so important..


Aerial Artificial type 1A

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  1. Aerial Artificial type 1A

Aerial Artificial type 1A


The Aerial Artificial type 1A is used in the RAF for aligning the output transmitter stage of the pre-war T 1083 for test purposes. This type 1A is a prewar type.

A schematic diagram is shown is picture 1. Note the different conections for the different frequence ranges.

It can also be used very easily for aligning the TR 1196 or TR 9.

Aerial Artificial  1A

The front and the electrical diagram.


The front of my set.


Here you can see the Artificial Aerial, used by the Australian Army in testing the transmitters,

type T-1083.

Aerial to be seen on the left on the shelve.

Kerst 2008 068


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  1. Transmitter/receiver TR 9-F

Transmitter/receiver TR 9-F

In working condition.


This is the pre war wellknown “SPITFIRE” sender receiver, type TR 9 F. Although the type 9 F is not used in it, but in the bigger aircrafts like Lancaster etc. for communication between the airfieldtower and the aircraft in close distance.

It is fully working in the 40 meter band with a crystal on 7078 Khz, amplitude modulated, by means of a intercommunication  amplifier, type A 1368. For using this amplifier, I had to make the connectors and the plugboard myself.

Normally a A 1134 is used. By lack of that type, to let it work, I used  the A 1368 intercommunication amplifier.

Question: can anyone tell me about the precise usage of the A 1368 in the RAF?,

Pse some info in the COMMENT at the end of the page.

Kerst 2008 069

The TR 9-F transmitter/receiver in all original condition.

Kerst 2008 068

In front the copies of the plugboard etc, for connecting the amplifier to the TR 9.

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Transmitter part, front..

Kerst 2008 065

Inside the transmitter.

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The power amplifier tube of the transmitter.

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The power amplifier anode coil of the transmitter.

RAF Walter


WALTER  tr 3180.

Air-Sea Rescue homing transmitter beacon

This is a very compact beacon used by crashed aircraftcrew from a single seater dinghy boat on the water. It operated on the Air ship to Vessel (ASV) radar beacon frequency of 177 Mhz. It signal could be received by airborne ASV mk2 radar sets or Rebecca mk 3b equipment in Coastel Command aircraft. The TR 3180 was a selfcontained unit, comprising a battery of 90 volts in waterproof case. earialmast and a smalltransmitter.
The earial was a small dipole type.
The range of the beacon was about 50 miles, if the aircraft was flying on an altitude of 4000 ft. The battery has a lifetime of 20 hours.


The whole case with the complete beacon, including battery case and transmitter with dipole antenna.


The transmitter  with erected mast and dipole. Above the dipole and transmitter, below the battery case.


The battery case. The wires are supplying the voltage to the transmitter.


The dipole antennal on top of the mast. In the middle the transmitter.


TR 1196

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  1. TR1196a,
  2. transmitter/receiver
  3. four channels.



four channels.

 Working condition.

This is a  transmitter-receiver used in airplanes like Lancaster etc. It is a four channel unit. For the receiver, as well as the transmitter, four crystals are used.

It is remote controlled by a switch box. On the picture a replica controll box is used. But the whole unit is working. Supply voltage is 12 volts, which indicates it is an earlier one.


Transmitter receiver TR 1196 a

Left the connection for the oxygenmask earphones and microphone. In the front the crystal types. At the right the replica remote control box, for choosing one of the four channels and controlling the transmitter.




Inside the unit.

Left receiverpart and right the transmitter part. See also there the HF coils for matching the energy to the earial.




At the right front the alternator power supply.


In front a good view on the crystal board of the transmitter.


In front the earial- and ground connection and the type plate. Also the Air Ministry mark. The white earia is a modification chart.


Left the transmitter with HF earial coils, for each channel one coil. In the mid the four tuning knobs for pre tuning the HF stages of the receiver for each channel.




An overview of the chassis.


A side view.


A nice paper layout picture  inside of the housing. It showes the components layout of the transmitterpart for service.


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  1. GEE


GEE was a Brittish wartime hyperbolic navigation system, used in bomber airplanes of Bomberc Command and airplanes of Coastal Command, like Lancaster, Halifax and Wellington. It was used to maintain the position of the airplane on their way to their targets, often Germany.

An short explainanation of GEE mapping:

By measuring the amount of calibrated pips on the indicator screen, between the  measured beacon pulses from different, fixed GEE transmitters along the country  (so each Gee transmitter gives a high pip on the screen) , and putting these  measurement amounts , called GEE units, in a GEE  map, man could determine the position of the airplane on the map itselves.Each measured GEE  unit has its own hyperbolic curve on that map. In principle, you have to measure 2 Gee units only. The crossing of each curve was the position of the airplane. For more accurency you used more Gee units, so more hyperbolic curves on the map. You have to interpolate the position by these different crossings.

On the internet this system is explaned very often and well.


The overview of my GEE installation.

Left the GEE receiver with frontend. The receiver is a type R 3645. It is a kind of MF receiver with videoamp. stage. The videostage signal  is fed to the indicator. This receiver picks up the beacon signals which are located on fixed places all in the brittisch countryside.

The frontend is a type 27 b. It converts a tuneable high frequency range of about 65 Mc till 85 Mc into a lower MF frequency of about 6,6 Mc.You could use differnt frontend for different frequency ranges.

In the mid the indicator type 266. On the CRT screen can be seen the beacon-, strobe marker- and calibration pulses.

On the right side the powersupply units, type” voltage control unit no 6″ with its “chokebox no 1″.

These units stabilise a 80 volts 1500 Hz voltage, coming from an alternator.


Here the original alternator, when I received it from an seller  in the UK, type UKX generator.

Normally it is mechanically driven by one of the airplane engines. It delivers the 24 volts DC and 80 volts 1500Hz. Because of the type it was possible to make it run in connecting the 24 volts parts to a 24 volt battery . All it takes about 30 ampere to let it run! In the left box on the generator (right box is 24 volts part with field connection) you could maintain 80 volts 1500 Hz.

The transformers in the receiver- and indicator powersupplies need a voltage of 80 volts 1500 HZ. The demensions of the transformer get smaller and the weight is less then when you use that frequency. Also other electrical equipment do so. Weight is one of the important fact in an airplane.


This is my alternator, type UKX. The little switch on the right is switching on a relay in the no 6 unit, which put the 80 volts on the receiver and indicator. The big switch is putting the 24 volt on the alternator.


Here the powersupply, type Voltage control panel 6, 5U/521. Above the Choke box type1.

These units stabilise the 80 volts from the alternator. Stabilising is needed because of the engine speed is often varying in some circomstances, so the voltage of 80 volts.

In front of it a “ground-flight” switch for switching the whole aircraft installation on the 24 volt from either outside the airplane or airplane batteries themselves. Now used to put the 24 volts on the UKX generator.


Here the receiver and indicator. On the receiver another frontend unit.



This is the screen of the indicator. You could see here the calibration pips and the negative strobe marker pulses. The measured pulses of the beacon transmitters, called A, B and C pulses are not to be seen. This ofcourse because the GEE systen does not exist any more. The last GEE transmitters went down in the end of the year 1960.

The strobe marker puls could be placed on different places along the X-axes by the red and white knobs  at the under side of the front.. By  Putting down the clearingswitch (you can see then the received beacon pules) you first bring the strobemarker puls just under the measured Gee beacon signals, the clearing switch up, you get the caibration pulses, after that you can measure the distance in calibrating pulses between the beginning of the scales and the strobe markerpulses. These differences are called the Gee units. So the position of the strobe marker at that moment is the position of the beacon signal, e.g. A, B or  C  beaconpuls.

I will once build my self a simulator for it, a schematic is already there etc.The it is possible to give a complete demonstration of the GEE navigation system.


Another look on the screen with a different time base. Watch the negative strobe marker pulses.


With the clearingswitch on the indicator, you get the noise  and the GEE beacon signal of the receiver on your screen of the indicator. With the red gainknob on the indicator on maximum, there will be a level of 2 cm on the screen.



Here, the noiselevel is somewhat lower by less gain on the indicator. The red gainknob is regulating the sensitivity of the receiver. When you are receiving the GEE master and slave signals, you can see also the the pulses of about 1 uS on the screen. But because the GEE system does not exist anymore, the pulses are absent.



Here the front of the GEE receiver, type R 3645. The switch “Z and N ” has an anti jamming function. Often the GEE signals were jammed, in the “Z” position a kind of CW jamming was suppressed then. When no jamming was there, the position of “N” was held. (Normal).

Nice is the lightened scale of the receiver tuning, which indicates also the powersupply is working.



The above side of the GEE 266. Tubes inside are the red VR91.



The side vieuw of the GEE 266.



The other side vieuw of the 266. Right above the EHT tube of the CRT. The compartment on the left under the crystals. On the below centre the MF coils strip of the receiver part.



Above the test set no 210.

This typical test set is used for testing and alighning the GEE installation. It consist of a HF generator, suitable for all the frequencybands of the RF units used in the GEE receiver. All frequency signals unmodulated.

Also a wideband noisegenerator for testing the receiver.

And most import a PRF generator. With this it is possible to generate 15 khz pips on the screen of the GEE indicator. In the test set, there is a generator, which is modulated (switched on and off) by a crystalcontrolled modulator/oscillator. This generator, with it’s frequency tuned on the receiverfrequency of the GEE receiver, is crystalcontrolled by 6 xtals. Frequency A till F. The frequency of the crystals are the same as in the timebase generator of the indicator, in this case the type 266.

By finetuning the PRF (the knob just left of the pilotlamp) on the testset, it is possible to synchronise with the timebase in the GEE indicator. When synchronised, the pips stand still on the screen.

The output of the testset is connected to the GEE receiver input by a coaxialcable.

Also a whip earial can be used, it consist of 3 parts.

The frequency of the generator can be tuned , by a tablechart, by the big black knob at the left on the front.



Here the 15 khz pips on the the screen of the GEE inicator, type 266. The clearingswitch on the indicator is up, position “receiving GEE signals”. The switch on the test at “modulation on”.


By adjusting the gain on the indicator, the noise level can be taken away, so that only the pips and the strobepulses are left.

The faulty part of the of the timebase at the left is probably a fault in the flyback phase or liniarity of the timebase of the circuit. I left it like that. For demonstrationpurposes it’s not so important.

R 1224

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  1. RAF  R1224 A

RAF  R1224 A


This is the RAF R 1224 A receiver. It is a superhet receiver. It is part of the Station W/T portable Type 9.

Frequency range was 1,5 Mc – & Mc.

Output impedance 2000 and 8000 ohm.

Heater voltage 2 volt.


R 1147A

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  1. RAF  spitfire receiver R1147A

RAF  spitfire receiver R1147A


The R 1147 receiver is a homing receiver for use in a Spitfire aircraft, spitfires of the RAF P.R.U. squadron. P.R.U. stands for Photographic Reconnaisance Units. At that time these Spitfires had no radio of any kind. The receiver was remote controlled by a mechanical bowdencable (splineshaft) from the cockpit. A Mark 5B stopwatch was included in the system package for timing the beacon signals.

This receiver only existed for a short amount of time, starting March 1941. They were loaned from the Royal Navy for a test in that year, because the PRU squadrons needed the use of homing at that moment. Because of the receiver’s weaknesses, they were eventually replaced by the TR 1133 in 1942. The TR 1133 also had communication possibilities.

Frequency range of the R 1147 is 180 Mc-220 Mc. and used a small whip antenna on the aircraft.






The picture above displays the cockpit’s remote control R1147 receiver. It was placed beside the pilot and connected through a splineshaft cable to the R1147. This remote control unit looks just like the one placed on the front of the receiver. Watch the tuning scale on the side of the remote control unit. Markers at A, B, C and D

R116A - 1

R 1116A pre war aircraft receiver.

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  1. R 1116A receiver,

R 1116A receiver,

a real museum piece.

This receiver, is what you call, a very old fashion radio receiver. A military design just after the “spark transmitters and receivers” episode  in WW1. They are very scarce to get now a days. That is why, it is one of my most favourite receivers in my collection.

The receiver is in an  entire original condition and working! Only the grid battery is a copy, see pictures below.

The R 1116A receiver is a later version of the R1116. It is a prewar aircraft receiver, which was used with the T 1115 transmitter. The aircraft was , for example,  the   British torpedo fighter “Swordfish”, which operates from aircraftcarriers at sea. The swordfish was wellknown  by actions against the German Bismarck, by attacking it with torpedo’s. Amazing fact is, that both the receiver and transmitter were placed just behind the pilot in the open cockpit. The pilot was also a radioman and gunner.

The receiver is a double superhet receiver. No  HF amplifier stage, just a tuned coil before the mixerstage,  first IF is 10,7 Mc, second IF is 100 Kc. The sensitivity is very well, and the bandwidth is small because of the 100 Kc frequency. Audio is sufficient because of the VR 35 final amplifier. My receiver is working very well . I’m using it also at the 80 meterband for AM, SSB and CW. Also provision is made for direction finding. The receiver can be switched  to 2  different parts, LF and HF. Each part can be switched into 3 different wavebands. Funny is, that the scale lightning  is changing by choosing either the LF or HF part, from the one to other scale.

The front of the receiver.


Another look at the under side of the chassis.  The LF stage and detector stage.


Just below the chassis Just left the variable condensors for pretuning the HF stage for the LF and HF part.


A simplified circuitdiagram of the receiver.  The diode at the input of the first mixer is for protecting the receiver for very strong transmitter signals. The diagram is only for one part and one frequencyband. It  has also a provision for an intercommunication  by means of the T7 microphone  connection. The preamp V6 and final  V7 is used then. V 8 is the CW oscillator. R 13 and R 16 are used for an external LF gain remotecontroll.


R 1082 pre war aircraft receiver.

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  1. R1082 receiver,
  2. A real museum piece.

R1082 receiver,

A real museum piece.

The receiver is all original from the out- and the inside.

Just like the R 1116 receiver, this is also one, which is a very scarce radio to get. A very simple design with only 2 tuned coils to determine the receiving frequency. One  for the HF stage, and one for the detektor stage. It is also, like the R1116 receiver, one of my favourite radio’s of my collection.

The R 1082 is a prewar aircraft receiver, used with the T 1083 transmitter. It is a TRF receiver , with 2 single coil  for each frequencyband.  One for the HF stage (below on the front) and one for the detector stage (above at the front). There are various freuqency wavebands.  The receiver could also been used for directionfinding purposes. For DF, at the head of the the HF coil, there is a symmetrical inputconnection for the cable of the loopearial. Directionfinding must be carried out  by means of  listing to the signal minimum. So no DF instrument. On the first picture a special (green) S-type coil (detector) is used. At the top of the coil, a spline cable for remote control can be attached. The meaning of this is only for readjusting the frequency a little bit. Only small  tuning is possible, otherwise you have to retune the HF stage also, when you make larger requency tuning.
It needs 2 volt fotr the heaters and 120 volts for the HT.


The above picture shows my receiver R1082. In front at the left the 2 volts heater battery and at the right  a couple of  coil sets for different frequency bands.


The receiver from the right side. Note  that  the aluminium case for the receiver  is put into a wooden case.


As seen above:  a close view of the front of the receiver. The cable for the PSU is homemade by lack of an original one.  The connector is made of a piece of teflon.



This is the coil set box, for the different frequency bands. A very hard to get box! Sure when it is complete and it is.


The schematic diagram.

R1082 a

The receiver R 1082 and transmitter T 1083 under test in an Australian Army service department.

Left the R 1082, right the T1083.