[time-nuts] 10MHz Rubidium reference source for frequency counter

John Miles john at miles.io
Sun Oct 26 17:28:24 EDT 2014

> Can I have your recommendation regarding a choice of 10 MHz rubidium source
> (available now on eBay like FE-5680; LPRO-101; LPFRS; FRS etc.) as a
> reference signal for my frequency counter Pendulum CNT-91.

You might take a look at the plots at http://www.ke5fx.com/rb.htm if you haven't already, and also at http://febo.com/pages/oscillators/rubes/ .  These will give you an idea what to expect from some of the popular Rb models.  The PRS10 mentioned by Said is a great choice for long-term measurements, but it's also the most expensive of the ones you are likely to find on the surplus market. 

Interestingly, if you want the best performance between 1 and 10 seconds the PRS10 is actually the worst of the ones I measured.  But the CNT-91 probably will not be able to see the difference, since its single-shot resolution is a bit worse than the HP 5370B counter (see attached plot).

Caveats: 1) No rubidium standard will give its best long-term performance until it has been allowed to run undisturbed for at least a few days.  2) These plots shouldn't be taken too seriously because of the (very) small number of examples tested under inconsistent environmental conditions. 

-- john, KE5FX
Miles Design LLC

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