• Country
• Great Britain (UK)

• Manufacturer / Brand
• MILITARY U.K. (different makers for same model)

• Year
• 1941–1944 ?

• Category
• Military transmitter

• Radiomuseum.org ID
• 271818

Click on the schematic thumbnail to request the schematic as a free document.

• Number of Tubes
• 9

• Valves / Tubes
• AW3 AW3 ATS25 ATS25 ATP35 ATS25 ARP34 AU1 EA50

• Main principle
• Transmitter

• Wave bands
• Wave Bands given in the notes.

• Power type and voltage
• Line (AC, UC or DC not known) / 100-250 Volt

• Loudspeaker
• - For headphones or amp.

• Material
• Metal case

• from Radiomuseum.org
• Model: Wireless Set No.12 Sender - MILITARY U.K. different makers

• Shape
• Boatanchor (heavy military or commercial set >20 kg).

• Dimensions (WHD)
• 24 x 12.5 x 17.5 inch / 610 x 318 x 445 mm

• Notes

• An HF transmitter used by the British Army in larger vehicles from 1940 onwards, with the accompanying R107 HF receiver. It produces about 25W in CW mode, and 7W in AM/RT mode. There are two models of the equipment: the Mk.I runs on line frequencies of 45 - 65c/s, and the Mk.II on line frequencies of 45 to 500c/s. Line voltages are 100 - 250V for both models.

  The frequency range is 1.2Mc/s to 17.5Mc/s in four overlapping bands. As well as CW and R/T (AM) modes, it includes a MCW mode to send Morse to receivers with no BFO.

  The main stages are (1) an oscillator, which can be crystal controlled or variable frequency running at half the output frequency, (2) a separately tuned multiplier/buffer amplifier, (3) a Class C power amplifier with a parallel tuned circuit output using a variable tapped inductor to match aerial impedances of 100 - 600 ohms, (4) a microphone pre-amplifier and 900c/s audio oscillator in MCW mode, (5) a modulator stage which is transformer coupled to suppressor grid of the PA valve, and (6) a rectifier to produce sidetone directly from the modulated RF output.

  This is one of the first British transmitters to improve on the older MOPA configuration by introducing an intermediate buffer stage, which is not there to increase the drive to the PA, but rather to isolate the VFO from the pulling effects of tuning the PA.  This feature, along with a stabilised HT supply to the VFO helped limit drift to a maximum of 3kc/s at 10Mc/s output frequency (300ppm).

  Accompanying equipment includes the R107 receiver, Aerial Coupling Units Type F and Type H, and Remote Control Unit Type C.

• Net weight (2.2 lb = 1 kg)
• 134 lb (134 lb 0 oz) / 60.836 kg

• Mentioned in
• Wireless for the Warrior; L.Meulstee (Volume 1, Chapter WS12)

• Literature/Schematics (1)
• -- Original-techn. papers. (EMER Tels D142 and D144, Jan and Feb 1945)

• Literature/Schematics (2)
• -- Original-techn. papers. (Wireless Set No.12 Mk.II General Description, Working Instructions, Aerials and Maintenance.)

• Author
• Model page created by Richard Hankins. See "Data change" for further contributors.

• Other Models

• Here you find 152 models, 120 with images and 48 with schematics for wireless sets etc. In French: TSF for Télégraphie sans fil.
  All listed radios etc. from MILITARY U.K. (different makers for same model)