• Year
  • 1917 ??
  • Category
  • Radio module pre 1926 (not a part, not a key)
  • Radiomuseum.org ID
  • 334763

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

 Technical Specifications

  • Main principle
  • RF-Circuit or wave trap (separate, can also be an antenna with amp.)
  • Wave bands
  • Broadcast only (MW).
  • Power type and voltage
  • No Power needed
  • Loudspeaker
  • - - No sound reproduction output.
  • Material
  • Wooden case
  • from Radiomuseum.org
  • Model: Loose coupler - Bunnell & Co., J.H.; Kings
  • Shape
  • Miscellaneous shapes - described under notes.
  • Dimensions (WHD)
  • 14 x 5 x 5.5 inch / 356 x 127 x 140 mm
  • Notes
    1. This is an loose coupler manufactured by the well known J.H. Bunnell & Co. pre 1919. The tuner comes from the Harold Greenwood wireless radio collection. Its paper Greenwood tag is undamaged and affixed to the underside of the base.
    2. The crystal receiver that use this coupler (see schematic) tunes from 600 KHz to 1410 KHz with the indoor 10 ft. antenna and a ground connection. With the moving coil completely outside and higher impedance static coil (left side) and moving coil switch at 0 position (right) the receiver tunes at 600 KHz. When moving sliding coil inside, the tuned frequency increase without touching any switch or variable capacitor. The tuned frequency increase also when the switch of the static coil is moved toward right, decreasing his inductance.
    3. A vintage “de Forest Crosley” 2 tube amplifier (2 x 201A tubes) is used on the test bench, in addition to high impedance (2000 ohms) headphones, as seen in related photos. 
    4. Measurements with a Rohde & Schwarz SM300 signal generator with the corresponding adapter for the impedance of a long wire antenna, shows a sensibility of around – 35 dBm over the AM band, with a decent signal to noise ratio in the headphones when the “de Forest Crosley” 2 tube amplifier is used. 
  • Net weight (2.2 lb = 1 kg)
  • 1.750 kg / 3 lb 13.7 oz (3.855 lb)
  • Author
  • Model page created by Serioja Tatu. See "Data change" for further contributors.

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The model Loose coupler is part of the collections of the following members.