Radio compass receivers,

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.

The compass receiver can be used  for communications, with a transmitter, type TA 12.



The direction finder SCR 269.


The remote control box of the SCR 269.


Aircraft receiver 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 Control box of the RA-1. 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 control. Watch the connector with cable at the right to the remote control MR-1B.


GEE navigation.

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.


In the mid, a view 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.

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.


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 demonstration purposes it’s not so important.

SCR 274 N – ARC 5 – AN/AR 8.

Aircraft radio SCR 274 / ARC 5.

The SCR 274 was the AAF, Army Air Force, radio installation, ment to use for short distances from one aircraft and the other. Also for communication in the neighbourhood of airfields.

Used in aircraft like Boeing B 17, the Flying Fortress.

The ARC 5 was used by the Navy aircrafts. Mostly, they were black in color, while the SCR 274 was just an aluminium color.

 SCR 274 N

This is my SCR 274 in working condition. On the left the 2 transmitters, in the mid the rotary transformer for the transmitters,  receivers and the controlboxes. At the right the ARC 5 VHF transmitter, type T-23/ARC5 and receiver type R-28/ARC5. Also on the right upper a control box, type C-30/ARC5, for the VHF receiver R-28 and transmitter T23.

Side view SCR 274 N

Above at the left  the antenna relay, 2 transmitters, 3 receivers, one rotary transformer for the transmitters and the control boxes.


Left the T-23/ARC5 transmitter.Inside very beautiful with the 829 B valves.


At the left an intercommunication amplifier, type AM-26/AIC. Also some spare items.

Marker-Beacon receiver AN/ARN 8


This is a very old Marker-Beacon receiver type AN/ARN 8. It is functioning on 75 Mhz and gives the pilot an indication of the position of the aircraft above the airfield’s runway during it’s landing process.

AAF Liaison radio

Liaison radio transmitter BC 375 E.

It was used in aircrafts like Boeing B17, B 24. during the second world war. Often in conjumction with the receiver BC 348.

It also uses a rotary transformer power supply, which I also own,  at  a voltage of 28 volts. Frequency bands could be chosen by different, so called tuningboxes. For working on a different frequency band, you had to pull out the tuning box unit in use from the transmitter and insert another one. All provisions were included in the transmitter to match the ouput stage to the end feeded longwire antenna.

It was placed just under the operators table. On the table the receiver BC 348 was positioned.

I use this transmitter often in the 80 meter amateurband on 3705 Khz in phone AM. Output power 100 Watts, anode-screen modulation by a carbon microphone. As a powersupply, I use a homemade mains supply.

BC 375 E

My BC 375- E  transmitter for 28 volts DC.

BC 375 buizen comp

Valves transmiiter, left VT 25, on the right four VT 4 C.

The VT 25 is the audio preampliefier. The most left VT 4 is the transmitter VFO and the other VT4’s are the audio power amplifier.Here the front cover of the valves compartment is removed.

The valves are glowing so much, you can almost read your newspaper in the light they are producing. A beautiful view, especially in the dark.

RAF H2S radar

H2S radar transmitters TR3191 and ASV MK7.

H2S was the British radar equipment on board of aircrafts of the Bomber and Coastal Command airforces in WW2 . The main part was a magnetron oscillator valve housed in a cavity resonator.

The type, seen on the pictures below, the TR 3191, was working on a wavelength of 10 cm. Later improved H2S systems were also used at a wavelength of 3 cm, like H2S MK 7, described at the end of this post.
The HF energy power was radiated from the bally of the aircraft to the ground by a tuned parabolic aerial. This earial was used by the transmitter and receiver part of the equipment. The reflected transmitted pulses, by the surface below, are getting back to the receiver input, rectified and fed to the indicator screen(CRT). On the CRT of the indicatorunit appears the forms of buildings, coastlines etc., were the aircraft is located above, just like on a map. So the crew/navigator knows then exactly the position of the
An  American version of H2S is the type H2X on 3 cm wavelength.

Of course H2S was most secret, so that is why a little explosive material, in a socalled detonator chamber ,  was put at the inside of the transmitter. In case of the possibl, falling into enemy hands of the aircraft over enemy territory, the explosive should destroy the inside of it. So knowledge about this technics, was kept away. The crew member could establish this by pushing a “detonator” button on the navigators panel, and electrically  fire the little explosive.

But you had to be very careful these days of war, with those units, found in aircrafts, which were shot down then . It was possible, that the crew members did not have the time to push the de detonatotor button in destroying the inside by means of those little explosives, when the aircraft was shot down.

H2S TR3191 front

  The front of my radar transmitter TR3191. which is complete and all original!  Also the case of it is it.

H2S TR3191 upper vieuw

 The upper view of the transmitter , with the fan for cooling the magnetron, below also the pulstransformer, which supplies the negative HT puls to the magnetron.

up Tr3191

At the left the diode mixer, where the signal from the reflected puls, coming from the antenna during the receive phase, is mixed  with the local oscillator signal, coming from the tuningunit 207 or from the indicator unit,  into a medium frequency signal. In the middle the rhumbatron, a TR switch, and at  the right the wave quide to the antenna outlet connector.

The switch is filled up with a gas and a little bit of water vapor. As soon, when the transmit phase is there, the high voltage puls is applied to the switch, the gas is conducting because of that puls and so cutting off the crystal mixer input. The reason for that  little bit of water vapor is to establish a quicker start of the conduction, so almost no energy is passed through.

The power energy, coming from the magnetron, is that high, it would damage not just the crystal mixer, but also the receiver input stage. So as a protection of it. Of course it  will let pass through the reflected pulsed frequency , during the receive phase, to the mixer. The gas in the switch  is not conducting in that phase.

Magnet magnetron

 Here the view of the magnet of the magnetron CV64, and the spark isolation shield. This spark isolation shield is nescessary , because of the high HF- voltage on the cathode side of the magnetron.Also to be seen,  the wavequide to the reflector feeder. The wavequide is matching the magnetron output impedance to the feeder impedance.

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Here is very well to see, that the magnetron fits in the first part of the wave quide inside. Inside the wavquide is to be seen, output stick of the magnetron.

foto 6

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The magnetron CV 64.                                          Copper coverplate removed.

foto 10

Diode mixer.

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                                                                                        Holder with diode removed.

A x-ray picture of the CV 64.  Here we can see the several resonator holes. These holes are made in a big piece of cupper material. In the most above resonator hole, you can see the energy output link.

H2S mk7A, a 3 cm wavelength ASV radar.

Another radar transmitter used by the RAF, was the H2S mk7A, a 3 cm wavelength ASV radar. The principle was the same as the TR 3191. ASV means Air Ship to Vessel.

The purpose was to detect the German war ships  and especially the U-boats, which were at the watersurface, for charging their batteries.

This type was the TR 3523, which I own too.

The feeder itself, the connection between the unit and the parabolic antenna was not a coaxial cable anymore, but a wavequide feeder.( kind of hollow pipe). This because of the the short wave length of 3 cm. Coaxial cable will reduce the energy  to the antenna too much. By using this very short wavelength, the picture on the indicator screen

 I managed to find a lot of spares. Some missing parts were among them. Some chassis parts, to mount the fan, to mount the missing magnet at the back of the unit , the ring to fasten the magnetron on the internal wavequide and some internal covers. So it is now a bit more complete.

I am still missing the following

The magnet unit for the magnetron,

The tube or pipe between the fan and the air inlet of the magnetron,

The impuls transformer with the integrated magnetron 725 A.  I now mounted a seperate magnetron in my own way, without the impuls transformer. See also the pictures. It is of course not original.

Some original wavequides or pipes to fitt on the outlet of the transmitter.

Who can help me with these missing items? It is all a bit very specialized and maybe it could be regognized only  by the specialists among us, but who knowes.

Pse your re. in the comment at the end of this post. I would be most grateful. I sure like to complete this rare historical ASV radar transmitter.

2335 a

Front of the TR 3523.  At the left under part of the front, you can see the wavequide output flens.

2335 b

Side view, with left on the picture the 725A magnetron, attached to the  inner wavequide. Also the fan for cooling the magnetron.

2335 c

H2S TX 3 cm

Another side view and the back of the unit. Here to be seen the glass bulb of the magnetron, normally this glass bulb is integrated into the pulstransformer, so you will not see the bulb, but the transformer.

A close view ofthe magnetron,  which outlet is attached to the wavequide by a ring. Note, that the magnetron is mounted on a metal plate, which is not original. This, because the impuls transformer on his mounting is missing.


The 725- A magnetron. At the upper right, the outlet flens of the magnetron. The square part , with at the right the outlet flens, of the magnetron is a cavity chamber (inductance), which  resonance frequency is at about 3 cm wavelengh.

Modulator unit, type 64.

This unit is a very important unit for the H2S installation. It is used in verious versions of H2S. One of the functions of it, is providing  the negative puls for the pulstranformer in the magnetron transmitter.

mod 64 front

The front of the modulator unit.

mod 64 unit

Inside view on the chassis.

RAF Lancaster

Lancaster radio- and navigator section with T 1154 and R 1155.


In the past, the idea came to do something else with the T1154 and R1155 collection, instead of putting it just on a wooden shelf or something. On several sites on internet I saw that some people made a complete Lanc mockup of these equipment. ( Jan and Paul Bodifee at Deventer Holland and Norman Groom in the UK). This was something for me. But I did not had so much room, I got to remove my other radio’s to some where else. That was not possible. So I had to make it more smaller than the others. So this is the result in a smaller size, but still very nice. Of course the navigator section just behind the the wooden board of the wireless operator had to be there! And of course the T1154 and R1155 had to be in fully working condition to work other radio amateurs.



A close look of the famous and well known T1154N transmitter. Left the aerial switch type J.




The position of the various electronic equipment inside the AVRO LANCASTER aircraft in the late war years 1944/1945.


This is a view of the radio section of the Lancaster shown at the Imperial War Museum in London. The photograph was taken by myself during a visit of mine. This was the start of the idea making a Lancaster mockup of my own.



The radio operator office. Left the antenna

current meter for the HF bands, also the aerial switch type J.

Note the microphone connector on the front of the transmitter above. This special connector is a very rare one, very difficult to get.



Here a good look on the tubes compartment of the transmitter. Left the VR 105’s of the VFO and modulator. Right the VR 104’s of the power amplifier.



 A fine look of the transmitter from below.


 Side view.



Left the plot for the headphone/microphone for the oxygen mask of the radio operator.





The receiver R 1155 A. Note the centric tuningknob, Later on the 2 knobs were concentric.

Again a good look on the radiotubes of the transmitter.



This is a more closer look of the A1134 intercom amplifier unit and the Plugboard type 192. This plugboard can be used to connect the amplifier to several other equipment in the aircraft like TR1196, TR 1143 or TR9 transmitters and of course to the headgear/micorphones of the crew. At the right the receiver R1155 A.



Another look on the A1134 intercomamplifier. On the left the switch for putting it on the intercomeline to navigator, airgunner, pilot or let it function as a speechamplifier for the radio transmitter T 1154. Right the on/off switch of the unit. A small user manuel for using the amplifier on the forward side of it. The amplifier is fed for the filement from a lead battery and for the HT from a small vibrator psu unit.


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This is the direction finder loop antenna on the roof of the cage. It is a replica of the original one. A big “steering knob” with scale, placed under the skin is for turning the loop antenna .



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This is the navigator office. Above the well known Gee set indicator type 62. On the middle the API (Air Position Indicator)  unit just above the table. Above in the mid the compass corrector.



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A view of the Air positioning Indicator left . On the right side on the front 2 mechanical counters for the longitude and latitude in degrees and minutes. A mileage unit, fitted below the navigator bench, converts the forward air pressure from the pitot tube ( an open ended tube facing forward in the air flow) into a rotary speed such that this speed is proportional to the airspeed of the aircraft. A flexible cable couples this rotary output to the API and together with an electrical signal (compass bearing) from the master  gyro compass, produces an output on the 2 counters on the front, that read directly in degrees and minutes.

On the back panel several instruments. Also the IFF buttons for destruction the inside parts of the indicator and IFF unit in case of a crash behind enemy lines. 

See also right on the panel, a call button switch/lamp for telling the radio operator that the navigator wants access on the intercom. The radio operator also has such a call lamp. He noticed that the lamp is burning, so the he connects the intercom amplifier A1134 , which acted at that time as a speech amplifier for the radio transmitter, to the intercom line. So also the air gunner or the pilot has a call button with lamp.


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On this view the VHF transmitter SCR 522 is shown. Normally it is not placed below the nav. bench, but I did so because of the lac of room. The TR5043 is the Brittish version of the American SCR 522 and in use in the later years of wartime. It is a 4 channel VHF set for “darky “communication, when the aircraft lost the navigation to the airfield. By this communication they could find there way back home when other communication equipment failed. Also visible is the control box withe the 5 red knobs on it. One for putting the set on (upper one) the other 4 for the choice of the 4 channels. Just below the switch for putting on the transmitter.

When nothing is working in the navigation installation, they could use the so called Bubble sextant at the right side of the table for determine the position of the airplane. This by the “old seaman way” by “shooting” stars in the sky and then reading the values on the sextant, then with these values determine you position on a map.

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Left the GEE Indicator type 62 A, right the GPI. at the left upper part of the picture again the compass corrector.

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The homemade tuning scale of the direction finder loop. The wheel is an original one. Above a cockpit lamp for illumination of the navigator office, which is not a replica..


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GEE receiver box with frontend unit ,below the voltage control panel no 3 as a regulator for the 80 volts – 1500 HZ from an alternator. The 80 volts is needed for the receiver box and the indicator unit.



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A front view of the radio compartment, showing also the airplane skin.

GEE 266

Another GEE-indicator type 266. Note the blue switch on the lower right This switch can select more crystals instead of the one of the earlier type indicator no. 62.. The 266 was a later improved version. Main changes was the internal EHT power supply. This power supply was not there in the type 62.

mockup 017

The two dynamotors for the receiver and the transmitter below the table. The upper is the HT dynamotor for the transmitter, supplying 1250 volts DC, that one below the dynamotor for the receiver supplying 6 volts and 220 volt. The power supplies are being fed by a main power supply of 230 volts 50 Hz.

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Picture above shows the 2 HT dynamotor supply units, the above for the transmitter and the below one for the receiver.
On the left a homemade 2 – 100 volt mains supply unit for the A 1134.

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The picture above is the crystal calibrator used in the Lancaster for calibrating the frequency of the transmitter T 1154. It is fed by the same 2 volt accumulator and vibrator power supply used by the A 1134 intercommunication amplifier.

Several internal crystals can be used, even a spare one at the front of the calibrator.


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The pictures above is the trailing aerial of the T 1154 transmitter for especially the medium wave frequencies.


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Note the small balls at the end of the wire. They are lead balls, to let the aerial wire going down easier  because of the weight of it.

The lead to the J-switch has to be very well isolated by isolation standoffs because of the high HF voltage. Because the small length of the aerial wire is too  short for it’s frequency, the HF voltage at the beginning of the aerial is very high.


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The wounded up aerial just under the radio operator table.

However, now a days, the mockup does not  exist anymore. About 3 months ago, I moved to another pace, a village about 15 km north of my former place. There was not room enough to rebuild it. I made a new setup. I kept all the item of it in my collection.

A picture is shown in the section “about”. But the T1154 and R1155  is still in working order. But as a remembrance, I left the mockup section  pictures and discription on this website.