Le 27 sept. 2013 à 21:16, Tom Van Baak a écrit :

> Hi Mike,
> 
> Cs tubes with "S" are standard-performance; tubes with "H" are 
> high-performance. You can get that from the tube label, or from the front 
> panel S/N. Don't trust the black dot on the rear of the instrument: frames 
> change, tubes change, Sharpies add dots, acetone removes them.
> 
> It depends on what you want the 5071A for. National labs keeping timescales 
> prefer the H tubes since they are several times more stable than the S tubes. 
> Casual labs prefer the S tube since they last much longer than H tubes. You 
> have a standard tube.

  I thought so, but the figures looked ok so I went for it anyway.

> The good news is that it appears to work. Surplus, working, 5071A are not 
> common.
> 
> Your frame and tube S/N are quite low, meaning old. But I don't know of a way 
> to tell if the instrument has been used a little or a lot during the last 20 
> years. There's no "running hour" meter in the tube itself, the hardware, or 
> the software so AFAIK there's no way to tell how used it is.

  Shame, especially considering that it must have cost around 50k new. 

> But do read:
> www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA484993
> www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA508048
> 5071A_FAQs_Symm_Web.pdf
> www.ke5fx.com/cs_life.pdf

 Thanks for these links. 

> 
> Your syst:print? output looks ok to me. It would be interesting if you 
> compared your 5071A 1PPS against a GPS timing receiver for a week or month. 
> Then I could tell you better how well your 5071A is working.

  That looks like a good plan. I was going to just discipline the PPS against a 
timing receiver right off , but it would be interesting to see what its free 
running perf is like before I tweak that knob. 

> 
> /tvb
> 
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