The article discusses various aspects of time and frequency measurement, including:
1. Hertz (Hz): The standard unit of frequency, representing one cycle per second. It’s used to measure the frequency of various phenomena like light, sound, and radio waves.
2. Heterodyne: A technique that generates new frequencies by mixing two or more signals together. It’s used to increase the resolution of time and frequency measurement systems.
3. High Frequency (HF): The radio spectrum range from 3 to 30 MHz, commonly known as shortwave. Frequencies like 5, 10, and 15 MHz are used for time and frequency radio broadcasts.
4. Hydrogen Maser: An advanced frequency standard that operates at the resonance frequency of the hydrogen atom (1,420,405,752 Hz). It offers better short-term stability than cesium standards, typically less than 1 × 10^-12 at tau = 1 s, and reaches a noise floor of approximately 1 × 10^-15 after about 1 day. However, its long-term stability may be comparable to or slightly worse than cesium standards due to changes in the cavity’s resonance frequency over time.
Keywords: frequency, stability, oscillator
