[time-nuts] Worst possible error on a rubidium

[Jose Camara]

	This is a very interesting question, same as "if someone can't
afford a GPSDO, Cesium or other time-nutty contraption, but buys a
second-hand, uncalibrated Rubidium as his primary timebase, how accurate
would it be"?

	One whole class of units, the 'programmable' or 'synthesized' ones,
have to be removed from this discussion, as it can theoretically be off as
much as the range of the DDS. It can only be considered after being properly
calibrated, programmed against a known primary or traceable secondary.

	Most units nowadays on eBay are rated 1E-9 to 2E-10/yr aging, so it
might be safe to assume none would be off more than 1E-8?

	It would be interesting for people to dig their aged Rb and post the
measured frequency against Cesium or GPSDO.





-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Dr. David Kirkby
Sent: Wednesday, July 13, 2011 2:15 PM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] Worst possible error on a rubidium

If an old random 10 MHz Rubidium oscillator is working (i.e. powers up, and 
eventually locks), what is the maximum possible frequency error it could
have?

Could it remained locked with an error of 1 part in 10^7, 10^8, 10^9, 10^10
etc?

I assume there are physical limits which would simply stop it functioning
too 
far from the correct frequency, but don't have much clue what they are.

-- 
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