Transmitter AD57/A

Marconi Co. (Marconiphone, Marconi's Wireless Telegraph Co. Ltd.), GB (not tubes - see also HMV His Master's Voice)

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  • Year
  • 1938 ?
  • Category
  • Commercial Transmitter (TX not Transceiver)
  • Radiomuseum.org ID
  • 365858

 Technical Specifications

  • Number of Tubes
  • 5
  • Main principle
  • Transmitter
  • Wave bands
  • Wave Bands given in the notes.
  • Power type and voltage
  • Powered by external power supply or a main unit.
  • Loudspeaker
  • - - No sound reproduction output.
  • Material
  • Metal case
  • from Radiomuseum.org
  • Model: Transmitter AD57/A - Marconi Co. Marconiphone,
  • Shape
  • Boatanchor (heavy military or commercial set >20 kg).
  • Notes

  • The Marconi AD57 was a dual‑band airborne and marine transmitter developed in the mid‑1930s for Imperial Airways aircraft (notably the Armstrong‑Whitworth Ensign) & maritime communication. It handled CW, ICW, and AM telephony modes, paired with the AD5872 receiver/DF system for long‑range operational and navigational communication. The output was roughly 65 W, suitable for long-distance HF contact.

    Construction and Power Supply

    • Enclosed in a cast aluminium alloy case on anti‑vibration mounts for aircraft/ship service.
    • Operated from a 24‑V DC aircraft supply through a motor‑generator (~3,500 rpm) providing 1,200 V HT and 12 V LT outputs.
    • Contained two complete transmitters: one for medium-/long-wave (MW), one for short-wave (SW).
    • Front panels & valve bays were easily removable for servicing.

    Medium‑Wave Transmitter (500–273 kHz)
    Modes: CW, ICW, AM
    Power output: ~66 W
    Range:

    • CW: 400 mi
    • ICW: 300 mi
    • R/T voice: 200 mi

    Main valves and functions:

    • Master oscillator: Marconi DET.6 triode – generated the carrier frequency.
    • Power amplifier: Marconi ACT.6 triode – boosted RF output to aerial power level.
    • Modulator: Marconi MHL.4 triode – provided grid‑leak amplitude modulation for voice; up to 60 % depth.

    Keying and modulation:

    • CW/ICW used negative HT line keying for clean signal shaping.
    • ICW modulation derived from a 1 kHz interrupter disc on the generator shaft.
    • AM modulation applied via the MHL.4 to the oscillator stage.

    Operator controls:
    Tuning condenser (with five pre‑set spots), CW‑ICW‑Telephony selector, aerial tuning & variometer controls, and neutralizing (“Neutrodyne”) adjustments.

    Short‑Wave Transmitter (17.76–4.00 MHz)
    Modes: CW only
    Power output: ~60 W
    Range: 500–3,000 mi (depending on HF propagation)

    Main valves and functions:

    • Master oscillator: Marconi DET.5 triode – frequency source.
    • Power amplifier: Marconi ACT.6 triode – RF output stage, similar to MW side.

    Control features:
    Five click‑stop oscillator presets, aerial tuning controls, wave‑range selector switches, and Neutrodyne neutralising. The same HT keying method was used for CW.

    Performance Summary

    Band Frequency Range Modes Output Typical Range
    MW 500–273 kHz CW, ICW, AM 65W 200–400 mi
    SW 17.76–4.00 MHz CW 60W 500–3,000 mi
  • Literature/Schematics (1)
  • -- Original-techn. papers. (Electrical and Wireless Equipment of Aircraft, 4th edition, 1941)
  • Author
  • Model page created by Gary Cowans. See "Data change" for further contributors.

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