page_title: Rubidium standard
hierarchical_section_title: Rubidium standard
caption_attribution_description: English: FE-5680A rubidium frequency standard or "atomic clock", manufactured by FEI Communications. About 5 inches long. It produces a "clock signal" consisting of a digital pulse signal with an extremely accurate frequency. The frequency is stable to 2x10-11 per day or 2x10-9 per year. It requires a warmup period of 5 minutes before the frequency "locks" and becomes stable. The frequency of the output may be adjusted to any frequency between 1 Hz and 20 MHz. The cheapest and most widely-used atomic clocks, rubidium standards cost a few hundred dollars. They are used to control the frequency of radio and television stations, the transmitters in cell phone towers, and in many scientific and military applications. Information from FE-5680A Data Sheet, Frequency Electronics, Inc.
context_page_description: A rubidium standard or rubidium atomic clock is a frequency standard in which a specified hyperfine transition of electrons in rubidium-87 atoms is used to control the output frequency. It is the most inexpensive, compact, and widely produced atomic clock, used to control the frequency of television stations, cell phone base stations, in test equipment, and global navigation satellite systems like GPS. Commercial rubidium clocks are less accurate than caesium atomic clocks, which serve as primary frequency standards, so the rubidium clock is a secondary frequency standard.
  All commercial rubidium frequency standards operate by disciplining a crystal oscillator to the rubidium hyperfine transition of 6834682610.904 Hz. The intensity of light from a rubidium discharge lamp that reaches a photodetector through a resonance cell will drop by about 0.1% when the rubidium vapor in the resonance cell is exposed to microwave power near the transition frequency. The crystal oscillator is stabilized to the rubidium transition by detecting the light dip while sweeping an RF synthesizer through the transition frequency.
context_section_description: A rubidium standard or rubidium atomic clock is a frequency standard in which a specified hyperfine transition of electrons in rubidium-87 atoms is used to control the output frequency. It is the most inexpensive, compact, and widely produced atomic clock, used to control the frequency of television stations, cell phone base stations, in test equipment, and global navigation satellite systems like GPS. Commercial rubidium clocks are less accurate than caesium atomic clocks, which serve as primary frequency standards, so the rubidium clock is a secondary frequency standard. 
  All commercial rubidium frequency standards operate by disciplining a crystal oscillator to the rubidium hyperfine transition of 6834682610.904 Hz. The intensity of light from a rubidium discharge lamp that reaches a photodetector through a resonance cell will drop by about 0.1% when the rubidium vapor in the resonance cell is exposed to microwave power near the transition frequency. The crystal oscillator is stabilized to the rubidium transition by detecting the light dip while sweeping an RF synthesizer (referenced to the crystal) through the transition frequency.
caption: Rb oscillator
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