Bendix aircraft transmitter TA 12.

Posted on October 26, 2021

The Bendix transmitter TA 12.

This transmitter is originally an American made aircraft transmitter, but also used in the British Royal Airforce (RAF). Aircrafts like Mosquitos.

The TA 12 has four frequency bands, one for longwave and 3 for shortwave. The funny thing is that each frequency band, has it’s own VFO, and only one poweramplifier for all of them, 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. Modulation art, A-G2 modulation. In the mid the earial current meter.

The four knobs at the left are the channel preselector tunings, for each wave band one. Left of the knobs are the channel numbers 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.

In the beginning, by lack of the original powersupply/modulator unit, type MT 28 BA , I used a separate modulator, homemade, with 2 valves 807 in the final. With Ronette crystal microphone. It was doing very well. Also a homemade mains powersupply is used.

But some time ago, I managed to buy one on EBAY, a MT28BA. See the pictures below.

Sideview with power connector.

Inside view with at the left the Audio PA amplifier valves, in the mid, the modulation transformer.

View components, at the right, the several fuses and the switch for switching from carbon mic to dynamic mic.

The unit had to be cleaned a bit and inspected. But nothing was wrong with it. The unit came also with home made cables and control box for working with the transmitter on AM, CW and MCW. For AM I used a T17 carbon microphone. Modulation deph 100 %. The noise level of the rotary transformer is not to heavy. It starts only at CW (contineously) and at AM (during transmitting).

Behind a small panel, you can chose by a switch, between a carbon mic or a dynamic mic. Note that at a type MT 28 B, this provision is not available.

Inside the transmitter.

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.

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

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

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 modulator unit is doing very well. In mode AM, I can make almost 100 % modulation depth. On CW, the tone is very stable. A pleasant way of working with it.

Aerial Artificial type 1A

Posted on October 31, 2014

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.

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.

TR 9F

Posted on October 31, 2014

Transmitter/receiver TR 9-F

The TR 9 is the pre war wellknown sender receiver. Although the type 9 F is was used in the bigger aircrafts like Lancaster bomber etc. for communication between the airfieldtower and the aircraft or in close distance to other ones. For fighter planes, the TR9 D is used, some slightly different. It was fully remote controlled bij bowden cables.

In the Lancaster, the TR9 F was positioned under the navigator table.

The TR9 D is different in use comparing it to the TR 9D. The TR9D is used in fighterplanes, while the TR9 F is used in bigger planes, like the bomber Lancaster.

Fighterplanes are one person planes, while bomber planes have more persons on board.

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 have 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 it is cinnected to the external mic . So in the TR 9 D the 3-stage audioamplifier can be used also as an intercommunication amplifier.

In 2 seaters fighterplanes, this intercom amplifier can be used.

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).

It is working now in the 40 meter band with a crystal on 7078 Khz.

The transmitter is a two stage transmitter, a crystal controlled oscillator and one power amplifier. The receiver is a TRF receiver. Also in the receiver part, a three stage audio amplifier for the headphones. This amplifier can also be used as a A3 modulator in conjunction with a preamplifier type A 1134.

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.

Inside the transmitter.

The power amplifier tube in the transmitter.

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.

TR 1196

Posted on October 27, 2014

TR1196a,

transmitter/receiver

four channels.

Working condition.

This is a transmitter-receiver used in airplanes like Lancaster etc. replacing the TR9 F in that place.

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, althoug also 24 volts systems exist. Which indicates that the 12 volt version 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. Behind the receiver.

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.