Micro condenser (or capacitor) in its original box with instruction sheet, used for neutralising radio frequency amplifiers, made by Sterling Manufacturing Co., Cleveland, Ohio, U.S.A. It has a maximum capacity of 5 Micro-Microfarads (pF) and cost US$1.00 to purchase in 1926.

Physical Description

A rectangular plastic plate with two triangular metal plates attached. There are two wire terminals. Manufacturer name is printed on the metal. The box is mainly yellow with blue printed text on all sides and a picture of the component. There is a folded piece of paper with printed instructions inside.

More Information

  • Collecting Areas

    Information & Communication

  • Manufacturer

    The Sterling Manufacturing Company, Cleveland, Ohio, United States of America, circa 1926

  • Inscriptions

    On condenser: " STERLING MFG CO.", " CLEVELAND USA " On box: " Sterling / R311 MICROCONDENSER / THE STERLING MFG. CO., CLEVELAND, O. U.S.A. ", " STERLING R311 MICROCONDENSER ", " MADE IN U.S.A. ", " Maximum Capacity / 5 Micro-Microfarads / Approximately " On instruction sheet: " Form 11 / Sterling / Equalizing Microcondenser / FOR / EQUALIZING TRANSFORMERS AND RADIO / FREQUENCY CIRCUITS. / Maximum Capacity approximately / 5 Micro-Microfarads / INSTRUCTIONS / To make adjustment, insert dry chisel / edged stick in slot in centre and turn / rotatable plate until required capacity / is obtained. / DO NOT USE SCREW DRIVER OR ANY / OTHER METAL IMPLEMENT. / 2 screws, 2 nuts and two wire terminals for / attachment enclosed. / STERLING MANUFACTURING CO. / CLEVELAND, OHIO "

  • Classification

    Communications, Radio, Components

  • Category

    History & Technology

  • Discipline


  • Type of item


  • Overall Dimensions

    48 mm (Width), 32 mm (Depth), 17 mm (Height)
    Overall dimensions of packaging box only.

  • Part Dimensions

    41 mm (Length), 24 mm (Width), 9 mm (Height)
    Overall Dimensions of condenser without packaging box.

  • References

    Advertisement in Popular Science, Mar 1926, p.120 states that the R-311 Sterling Microcondenser "is invaluable for increasing the grid to plate capacity with 199 and 299 tubes and is extensively used for equalizing radio frequency circuits." The price of the component was US$1.00 in 1926.

  • Keywords