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.

“Pip Squeak” American/British

American 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 important..

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.

The Artificial Aerial to be seen on the left on the shelve.


Transmitter/receiver TR 9-F


A short historie of the TR 9 and his successors.

The TR 9 is the pre war wellknown sender receiver.  Although the type 9 F is was used in the bigger aircrafts like the early Lancaster bomber etc. for communication between the airfieldtower and the aircraft or in close distance to others. The TR9 D is slightly different. It was fully remote controlled bij bowden cables. The TR 9 (D) were used in the Spitfire and Hurricane.

The TR9 F and D were especially used in the beginning of the war, in the battle of Brittain. Although his succesor, the TR 1133 was already there. The TR9 was in use in the Battle of Brittain instead, but not his succesor TR 1133, which supposed to be. The production of the TR 1133 was to small to deliver enough sets for the RAF at that time. They needed more transceivers for their increasing amount of fighters.

The TR 1133 was a VHF set with a frequency cover of 110 – 120 MHZ, and an output of about 5 watts, instead of that the TR 9 providing only 0,5 watts. The increasement of output was a big advantage.

The TR 1133 was already in use in the Spitfire and Hurricane at the withdrawal of the British army at Dunkirk in the beginning of the war. During the withdrawal the sets were all disadmantled out of the left behind airplanes, to avoid that they became in enemy hands.

But the TR9 stayed in service till after the battle of Brittain. Before the TR9 was superseeded after the battle by the TR 1133, the TR 1196 was introduced. The TR 1196 has a frequency range of 4,3 – 6,9 MHZ. The advantage of the receiver of the TR 1196, was that the receiver was crystalcontrolled.

After the TR 1196, came finally at the end of the war the TR 1133, a VHF set. But the TR 1133 was not so succesful and was soon replaced by the TR 1143.

Because there was a big cooperation between Brittain and the USA, they gave the design of it to the Americans. The designed the SCR 522 , with receiver the BC 24, and transmitter BC 625. It was almost the same design like the TR 1143. It was almost equal, even the typical british jones plug were used.

The SCR 522 was also used by the RAF in their fighterplanes.

Some technical details:

In the first early Lancasters, the TR9 F was positioned under the navigator table. And was used by the pilot for communication between airfield tower or between the squadron airplanes.

In the TR9D, the receiver type R1120 and the transmitter type T1119 is used, while in the TR9F the receiver type R 1139 and transmitter type T 1138. The receivers have the same schematic, but the transmitter has a different schematic. It is the internal connection I/C which is in the T 1138 is not connected, while in the T 1119 is. The I/C connector is an extra connection to input of the 3-stage audio amplifier in the receiver. In the T 1119 transmitter the I/C is connected to the external mic . So in the TR 9 D the 3-stage audioamplifier can be used also as an intercommunication amplifier.

In the T 1138 transmitter the external mic is connected to the micc transformer V3. This external mic connection can be connected externally to an A 1134 intercom amplifier acting as a preamplifier for an dynamic microphone. This for modulating the transmitter in mode A3 (anode/screen modulation).

My TR8 F It is working now in the 40 meter band with a crystal on 7078 Khz. It gives 2 mA on his antenna current meter into a Aerial Artificial no 1 A. ( See also the post Aerial Artificial no 1A). That supposed to be about 0,5 watts.

The receiver is a TRF receiver. It consists of two HF amplifiers, VRSG 18. Backfeed could be arranged in the second HF amplifier. This is arranged by a variabel condensor, which can be tuned on the front of theTR9. Called reaction.

A VR 21 is used as a triode detector. Followed by a three stage audioamplifier with also VR 21 triodes.

The transmitter is a three stage type and crystal controled.

One VT 20 as a crystal oscillator , A second one, VRSG 18 as a power amplifier. Also a a VRSG 18 as a modulation amplifier for A3 mode.

The transmitter has 2 channels. One is the normal channel N for communication and the S channel is the special frequency channel, which could be used for  PIPSQUEAK purposes. This system is discribed in the post PIPSQUEAK.

The front of the transmitter. 

Kerst 2008 065

Inside the transmitter.

Kerst 2008 064

The power amplifier tube in  the transmitter.

Kerst 2008 063

The power amplifier anode coil in  the transmitter.

The front of the TR9 F. Left the transmitterpart, right the receiverpart.

The intercom amplifier, type A 1368 connected, by lack of the original used amplifier type A 1134, to a homemade plugboard. My A 1134 is used for the T 1154 transmitter.

The front of the A 1368. Note the missing switch at the left , which is there at the A 1134. The amplifiers are the same, with same radio valves, same powersupply voltages 2 volt DC and 120 volt DC. Only the connector on the plugboard are smaller ones. So my plugboard can not be used with the A 1134.

Board with headphones connection, psu connection and the volume gain knob. The volume regulates the Second grid of the HF amplifier of the receiver.

This is a picture of a TR 9 in the Science museum. Probably the TR 9 D for fighterplanes, Spitfire, Hurricane. Watch the remotecontrole with bowden cables and in the mid the volume gain control. The remote control is extremely rare and hard to get.

The above pictures the setup of the TR9D in larger airplanes, like the Lancaster bombrer.

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 antenna on top of the mast. In the mid the transmitter.



The Funksprech F is a transmitter/receiver for use in armourned car vehicles. For example the Panzerspah wagen.



My Fusprech F.

Fusprech F overview

Left below in the picture  the headphones type DFH-b, at the left below the throat microphone..

Frontcover Fusprech.

The inside of the frontcover with an overview of the installation. Just click at the picture to enlarge and seeing it.

Russland, Funker in gepanzertem Fahrzeug

A radio operator controlling the radio in a armoured car, a “Panzer Spah Wagen”, in Russia during WW2. Probable, seeing  to the second person, there  an attack with mortar  in the neighbourhood?  Watch also the mark on  at his uniform of the left person ,telling us, he was a radio operator,  or called “Funker”.

Stern Antenna.

This antenna was very often in use in radio vehicles of the German Army. There were more types of them, some smaller ones, used on tanks.

I did use the antenna once, to see how the results were. I putted it on an isolated mast at a height of 4 m above the ground and managed to match it to my modern transciever by means of a 4 meter single  feeder to  a little tuner. Only in the 15 meter amateurband it was possible. AT good propagations I manage to work amateurs through all Europe. Only the principle of functioning is not all clear to me.

I think it is a toploaded vertical. Only the vertical part, being the 4 meter feeder to the tuner , is radiating?  The “Stern”is only a toploading or top capacity for a better matching?  Or is the “Stern” also radiating in a horizontal way. For me an open question.

Origina,l the antenna was ment to have a good  range and signal strenght  at nearby. Not suitable for skywave transmissions.

But my experience was quite different, just suitable for skywave.

Maybe someone can tell me. I only got an explanation of the principle in the books about Russian radio after the war. (Gunther Fietsch).

Stern antenna

The Stern Antenna in use in the back of my garden. Just below in the picture the 4 meter feeder wire to the tuner.