[HN Gopher] HP 5061A Cesium Clock [video]
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       HP 5061A Cesium Clock [video]
        
       Author : brudgers
       Score  : 28 points
       Date   : 2020-03-25 05:02 UTC (17 hours ago)
        
 (HTM) web link (www.youtube.com)
 (TXT) w3m dump (www.youtube.com)
        
       | MUHAMMADRIZWAN wrote:
       | https://thekrjaan.com/tiktok-videos-how-to-download-tiktok-v...
        
       | fsh wrote:
       | Amazing piece of technology. Its successor, the 5071A (now made
       | by microsemi) is still the most common primary frequency
       | standard. HP used to be such a great company. Now they make
       | crappy consumer printers and network cables with DRM chips.
        
         | jimmySixDOF wrote:
         | These things used to be critical elements in optical
         | transmission for circuit switched telephone networks
         | (SONNET/SDH). The old "5 9's" Reliability commitment ment your
         | Stratum clock was working across the whole ring. Now you just
         | throw a GPS antenna on every base station !
        
           | willis936 wrote:
           | You still need low phase noise local oscillators. Both atomic
           | standards and GPSDOs use ovenized crystal oscillators (double
           | ovenized if they're fancy).
           | 
           | It blows my mind that at the end of the day, the lowest noise
           | method of single frequency electrical signal generation we
           | have is a mechanical system.
        
         | Gibbon1 wrote:
         | HP spun off the good parts in 1999 to form Agilent. The Test
         | Equipment division was spun off in 2014 as Keysight
         | 
         | https://en.wikipedia.org/wiki/Agilent_Technologies
         | https://en.wikipedia.org/wiki/Keysight
        
       | abjecton wrote:
       | I find this video quite interesting.
       | 
       | I had no idea how Cesium clocks work, other than the SI
       | definition of a second is 9xxxx transitions between two states of
       | a cesium atom.
        
         | fsh wrote:
         | "Transition frequency" seems to be a common source of confusion
         | here. In the context of the SI definition it means "frequency
         | corresponding to the energy difference between the two states".
         | This is the frequency of radiation that can _most efficiently_
         | drive transitions between the states. How fast the atom
         | transitions between the states depends on the frequency,
         | polarization, and power of the driving radiation and can in
         | principle take any value. To avoid confusion this is called the
         | "Rabi frequency" in atomic physics.
        
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       (page generated 2020-03-25 23:00 UTC)