[time-nuts] What sort of oscillator is this?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 28 September 2014 15:52, David McGaw <n1hac at dartmouth.edu> wrote:
> The temperature stability and warm-up time imply an OCXO.  0.05ppm over
> 0-55C is at the limit of what can be achieved with a TCXO but they do not
> have a long warm-up time.  It would be expensive and only would be used if
> warm-up time was critical.  The HP high-stability options are (almost?)
> always OCXOs.
>
> David

For what it is worth, the calibration certificate indicates the
oscillator was warmed up for at least 48 hours, but the spec on the
instrument shows nothing like that.

Here's the latest cal certificate from Keysight.

http://www.kirkbymicrowave.co.uk/cal_certificates/Keysight-standard-calibration-with-uncertainties-for-8720D-vector-network-analyzer-16-09-2014.pdf

Note the section on the last page

OPT 1D5 HI STAB TIMEBASE PASSED
Elapsed time after power-on: 48 h

Here's the previous one from Agilent.

http://www.kirkbymicrowave.co.uk/cal_certificates/Agilent-standard-calibration-with-uncertainties-for-8720D-vector-network-analyzer.pdf

It sort of implies they left it on for 48 hours since it has that
oscillator, but I can't see anything in the specs to say it needs 48
hours to warm up.

BTW, you may note Keysight's uncertainty for measurement of the 10 MHz
reference in September 2014 is 0.0010 Hz, whereas Agilent's was
0.00080 Hz in August 2013. They 5071A primary frequency standard. I
assume the fact that the ID number is UK13623 on both certiciates,
means it is actually the same standard, rather than two of the same
model number.

Dave