[time-nuts] Difference between Datum 4065, A, B & C Cesium T&F standard?

[Brooke Clarke]

Hi Tom:

It's been my experience that to get into the E-13 E-14 range with GPS takes 
weeks and even then you don't have a strong sense that the data is good.

Is there a way that GPS can be replaced by another Cesium standard, like a 
FTS4060/S24 whose frequency is close but unknown?

I would think that since the 4060 does not drift (being Cesium) and if left on 
all the time during the test it's frequency should always be the same to much 
better than parts in E-14.

So a time interval measurement made to compare the two sources would give the 
desired results much faster.

Have Fun,

Brooke Clarke
http://www.prc68.com/P/Prod.html  Products I make and sell
http://www.prc68.com/Alpha.shtml  All my web pages listed based on html name
http://www.PRC68.com
http://www.precisionclock.com
http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Web Cam


Tom Van Baak wrote:
>> A two way RS-232 interface allows not only reading a bunch of 
>> operational parameters but also setting a number of things.  This 
>> could be GPS disciplined using RS-232 to tweak the frequency.  Maybe 
>> that's how the Frequency Offset came to be non zero.
> 
> 
> Brooke,
> 
> Yeah, that offset is pretty high. Someone might have played
> with it, or used the 4065B as an offset generator, or maybe
> deliberately set it a bit off-frequency to improve time-interval
> averaging statistics. Or like you said, used the offset to make
> small periodic phase adjustments as part of a CsGPSDO.
> 
> When you get a Cs standard that is inherently stable down in
> the -13's or -14's you can also use the programmed frequency
> offset feature to make relativistic corrections (about +1e-16
> per meter above sea level). For example, my house is at
> elevation 1000 ft (~ 300 m) so I would set my Cs freq offset
> about -3e-14 to compensate. But verify the long-term stability
> of the standard before you worry about subtle details like that.
> 
>> I don't have a feel for how well the automatic adjustments actually 
>> work, maybe  Tom can comment?
> 
> 
> I haven't done that with my 4065B yet so could you take a few
> days to try it on yours? Just power it up cold and measure it
> against GPS for a few days to get the mean frequency error.
> 
> Then repeat this half a dozen times and see what the "retrace"
> error is. Depending on the actual stability of your 4065B, and
> the resolution of your GPS and TIC, you might have to extend
> each run for a lot more than a couple of days.
> 
> As for your subject question, sorry, I don't have a handy list of
> model number differences.
> 
> /tvb
>