[time-nuts] 10811 performance

[Tom Van Baak]

Hi Robert,

If your 10811 10 MHz oscillator is off by 0.08 Hz after 20 years it's 
equivalent to an average frequency drift rate of only 0.08/1e7/20/365, 
or 1e-12/day. If so, you have an absolutely superb 10811; one that's 
500x better than spec. Congrats! Don't power it off, don't touch it, 
don't move it, don't tilt it, don't sell it.

Still, there are a lot of assumptions here:

- Do you know how closely was it calibrated 20 years ago?
- Did anyone measure it once a month or even once a year since then?
- Do you have reason to believe the frequency drift rate is constant or 
predictable?
- What's the environment been like (temperature, humidity, pressure)?
- How much do you trust your cheap China GPSDO?
- What does your 53131A counter say over gate times of 10 s or 100 s, 
and over an entire day or week?
- Was this a one-time lucky measurement or is your 10811 really this 
good day after day after day.

Lots of questions. What I mean is that you may have one of the best 
10811 ever seen, or something's funny with the above assumptions. The 
nice thing about a precise time & frequency hobby is that, without too 
much effort, you can figure this out.

Still, 0.08 Hz out of 10 MHz is 1e-8, or 0.01 ppm, or 10 ppb, so 
depending on the accuracy that you need for the amateur radio club, it 
may be plenty good enough as-is.

/tvb



On 12/26/2019 8:51 PM, Robert DiRosario wrote:
> I am trying to calibrate some equipment at the amateur radio club at 
> work, and my stuff.  We have an HP 5340A with a 10811 inside. It must 
> have been upgraded at some point in the past, the display uses Nixie 
> tubes.  I calibrated it c2000 using a HP Cs standard. That lab and 
> it's equipment are gone.  :-(
>
> From ebay / China I got a simple GPSDO that uses a Trimble 57963 
> inside.  I use the output of the 10811 in the 5340A to drive an HP 
> 53131A.  I then measured the 10 MHz output of the GPSDO using the HP 
> 53131A and got 10,000,000.08 Hz.
>
> Assuming the GPSDO is correct, is 0.08 Hz drift over 20 years a 
> reasonable amount of drift for an 10811?
>
> I have an HP Z3801A, once I get a power supply for it I can check the 
> other GPSDO.
>
> Thanks
>
> Robert
> KA3ZYX
>
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