Double frame direction finder P-711

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The double-frame direction finder system P-711 is a shortwave radio direction finder system that was used in radio companies in the Swiss Army from 1949 to 1970 . P-711 was used to locate ground transmitters over long distances. It could be operated both mobile (mounted on vehicles) and stationary.

The Swiss Army used a total of five P-711s in the radio location service , two of which were mobile and three were stationary in so-called Peilhütten. The supplier was the Swiss Hasler AG in Bern (Marconi agency for Switzerland).

Technical specifications

  • Development and manufacturer: Marconi Wireless Telegraph Co. Ltd., Chelmsford . Marconi factory name: DFg 29
  • Operating modes: broadcast reception, bearing reception, side determination
  • Frequency range: 2.5–12 MHz ( short wave )
  • Frequency selection: adjustable in 3 ranges
  • Modulation type :
    • A1A Morse code, soundless, carrier keying
    • A2A Morse code, amplitude-modulated subcarrier
    • A3E speaking, amplitude modulated carrier
  • Tubes : U 52, STv 280/40, 5 × EF 50, 3 × 63 KTW, DH 63, L 63
  • Antenna: Loop antenna with 2 antenna loops (double loop antenna), each 27.8 dm², at a distance of 2.43 m from one another
  • Receiver principle: Superhet HF, mixer, oscillator, 2 × IF, BFO, demodulator NF
  • Intermediate frequency : 465 kHz with coil filter
  • Selectivity: ± 3 kHz at −6 dB
  • Power supply: mains voltage 220 V 50 Hz, accumulator 6 V (with converter ), alternatively: generator
  • Dimensions: (WHD) 550 mm × 350 mm × 700 mm
  • Weight: 60 kg compl. Unit with receiver, antenna drive and bearing scale plus 16 kg of the antenna system

source

  • Hasler AG: Operating instructions double-frame direction finder system, 1950

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