• Country
• United States of America (USA)

• Manufacturer / Brand
• Radio Shack (Tandy, Realistic, Micronta); USA

• Year
• 1977

• Category
• Kit (Parts plus instruction) or building instructions only

• Radiomuseum.org ID
• 336027

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

• Number of Transistors
• 2

• Semiconductors
• 2N3904 2N3904

• Wave bands
• Wave Bands given in the notes.

• Power type and voltage
• Dry Batteries / AA: 3 x 1.5 Volt

• Loudspeaker
• - - No sound reproduction output.

• Material
• Plastics (no bakelite or catalin)

• from Radiomuseum.org
• Model: Science Fair Frequency 100 kHz Standard Cat. No.= 28-140 - Radio Shack Tandy, Realistic,

• Shape
• Very small Portable or Pocket-Set (Handheld) < 8 inch.

• Dimensions (WHD)
• 5.25 x 3 x 4.5 inch / 133 x 76 x 114 mm

• Notes

• The Science Fair Frequency Standard 28-140 is a crystal controlled 100 kHz oscillator with harmonics.  It is adjustable so as to zero-beat using a companion receiver for a frequency such as the 10 MHz signal from WWV.   It is one of a series of plastic chassis kits offered by Radio Shack known as "P-Box" kits, a name which was originally called a Perf-Box, made of a plastic that could withstand soldering temperatures.

• Price in first year of sale
• 9.95 USD

• Mentioned in
• Radio Shack Catalog (1977, page 162)

• Author
• Model page created by Rich Post. See "Data change" for further contributors.

• Other Models

• Here you find 1294 models, 1176 with images and 112 with schematics for wireless sets etc. In French: TSF for Télégraphie sans fil.
  All listed radios etc. from Radio Shack (Tandy, Realistic, Micronta); USA