[time-nuts] Low Allan Dev Oscillators

Bob Camp lists at rtty.us
Mon Sep 2 09:28:45 EDT 2013


Hi

…. but to the point he was making, those oscillators do "parts in ten to the thirteenth" not "sub one part in ten to the thirteenth". To be sub one part in the thirteenth the units on the a dev plot would have to be parts in ten to the fourteenth. Given the limits of email and fonts, the first probably would be X.X x 10^-13 and the second would probably be < 1.0 x10^-13. Neither one is correct in a scientific journal, but superscripts don't do well cross platform in email messages.

That's not to say those are bad OCXO's in the plots. Indeed they seem to be doing pretty well. By no means am I knocking the parts on your plots. 

Coming back to the BVA conversation, some of them do indeed meet a < 1.0 x 10^-13 specification for tau's in the 1 to a few hundred seconds range. Again, plotted on a graph, the units on their ADEV plots would be 10^-14 rather than 10^-13, since they are below 1.0 x 10^-13. 

I realize that's being a bit pedantic. However without getting the units / numbers / specs right, the whole BVA conversation does not make any sense.It's all about being an order of magnitude better than what you can typically get. 

Bob

On Sep 2, 2013, at 6:00 AM, Martyn Smith <martyn at ptsyst.com> wrote:

> Hello,
> 
> I mentioned about there being other low Allan Dev oscillators available on
> the market.
> 
> Said asked me to supply some results (And Yes Said, I meant 1 x 10E-13)
> 
> I'm not sure if attachments work on timeouts, so I have put a couple of
> graphs on my website.
> 
> These graphs show typical results for our low noise 10 MHz oscillator.
> 
> This oscillator hasn't been optimised specifically for Allan Dev or phase
> noise, just the best combination of both.
> 
> We can achieve better phase noise at 1 Hz, -120 dBc being achievable, if we
> select the best oscillator from a batch.
> 
> And the Allan Deviation is only after the oscillators have been on a day or
> so.  They will improve if left on longer.
> 
> www.ptsyst.com/10MHzPN-1.pdf
> 
> We have improved the phase noise at 100 Hz and get about -156 dBc these days.
> 
> www.ptsyst.com/10MHzAD-1.pdf
> 
> Best Regards
> 
> Steve
> 
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