Short-Wave Booster

Postal Radio, New York

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  • Year
  • 1934
  • Category
  • RF (Radio Frequency-) Amplifier
  • Radiomuseum.org ID
  • 354577

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

 Technical Specifications

  • Number of Tubes
  • 3
  • Main principle
  • Radio Frequency Amplification only
  • Wave bands
  • Short Wave (SW only)
  • Power type and voltage
  • AC/DC-set / 110 Volt
  • Loudspeaker
  • - - No sound reproduction output.
  • Material
  • Metal case
  • from Radiomuseum.org
  • Model: Short-Wave Booster - Postal Radio, New York
  • Shape
  • Tablemodel, with any shape - general.
  • Dimensions (WHD)
  • 8.75 x 10 x 6.25 inch / 222 x 254 x 159 mm
  • Notes

  • The Postal Short-Wave Booster has the following features:

    • Two-Stage SW TRF Preselector-Booster for TRF or Superheterodyne SW radios.
    • Boosts the tuned SW signal, which is then connected to the SW radio antenna input.
    • SW frequency is tuned with the booster's TRF 2-gang tuning capacitor and tuning coils.  SW Radio should be tuned to the same SW band and frequency as the booster.
    • Front panel SW TRF tuning coils are removable to select the SW bands:
      • "A"   14-29 meters (10.3-21.4 MHz)
      • "B"   29-55 meters (5.4-10.3 MHz)
      • "C"   55-90 meters (3.3-5.4 MHz)
      • "D"   90-200 meters (1.5-3.3 MHz)
    • May be powered by 110V AC or DC; 200 Ω line resistance power cord.
    • Power switch: On / Off.
    • Volume control.
    • Rear terminals: Antenna In +, Antenna In -, GND.
    • Shielded cable pigtail to the SW radio: Antenna Out, GND.
    • Antenna Select switch: Booster On (Antenna In + to booster, booster output to Antenna Out) / Bypass (Antenna In + direct to Antenna Out).
    • Price was $19.95 USD with one band of TRF tuning coils (without tubes), tubes were $1.95 USD, extra TRF tuning coils were $3.95 USD for each SW band.

    Note that with this design, there was no AC input isolation power transformer and one side of the AC/DC source is connected to the chassis/GND. The B+ voltage was limited to about 90V. If using a 110V DC source and the Booster does not work, reverse the DC leads.

    A safety or damage issue exists under this condition:

    • Booster GND is connected to the SW radio GND, and
    • Booster and SW radio are AC powered, then
    • Since the AC plugs are not polarized, there is a 50% probability that the AC Line will be shorted to the AC Neutral/GND.
    • Unless both units are plugged into the AC outlets with both AC Lines connected to chassis/GND or both AC Neutral/GNDs connected to chassis/GND, the AC Line from one unit will be shorted to the AC Neutral/GND of the other unit, which will cause damage to the units and/or house electrical wiring.

    This safety issue was likely one reason that next year's Booster model was redesigned to include an AC isolation input power transformer, thus isolating AC Line and Neutral/GND from the chassis/GND. Postal stated that the reason for the redesign was to increase the B+ voltage to about 200V for greater gain and selectivity.

    The new 1935 model was the Postal Improved SW Booster.

  • Price in first year of sale
  • 19.95 USD
  • Mentioned in
  • -- Original prospect or advert (Radio World, March 17, 1934, page 22 "announces a new Booster")
  • Literature/Schematics (1)
  • Radio Craft (June 1934, pages 735, 758 schematic & description, 754 ad.)
  • Literature/Schematics (2)
  • -- Original prospect or advert (Short Wave Radio, June 1934, pages 37, 39 schematic & description, 45 ad.)
  • Author
  • Model page created by Jerry Elarton. See "Data change" for further contributors.

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