This is very interesting. The 5061A is a Caesium standard- I don’t think there is anything Rubidium in it.
At Droitwich, I thought the first atomic frequency standard there was a Rubidium, or was this the Efratom units- as they did Rubidium?
Rubidium is, of course, not a primary standard; NPL used to publish the error in the Droitwich frequency each week. They don’t do this nowadays- I think because Droitwich uses a GPS locked standard, so there should be no error in average frequency.
Have I got this right?
There was an amusing incident last year, when I noted a considerable error in Droitwich frequency, which after observing for a few weeks I mentioned on another forum- error went to zero, a couple of days later.
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