[time-nuts] What are HP High Stability Oscillators (Option 1D5 in 8720D VNA)

[Magnus Danielson]

On 08/27/2012 10:14 PM, David Kirkby wrote:
> I recently bought an HP 8720D 20 GHz VNA with options 010 (TDR
> facility) and 1D5, which is the high stability time base. It's a
> fairly old VNA (not supported since 2004), but it's not exactly a
> dinosaur
>
>
> Accuracy (23 deg C +/- 3 deg C) 10 ppm
>
> The standard oscillator specs are:
> Stability 0 - 55 deg C
> 7.5 ppm
> Ageing per year = +/-3 ppm
>
> The high stability time base, option 1D5 are:
> Stability 0 - 55 deg C
> +/- 0.05 ppm
> Ageing +/- 0.5 ppm
>
> Resolution 1 Hz.
>
> What is likely to be the difference in design between the standard and
> high stability oscillators?
>
> It seems that while the optional timebase is more stable, this does
> not appear to reflect in the accuracy of the instrument, which is
> specified as 10 ppm. Perhaps that's due to the fact that the steps are
> 1 Hz, and the synthesiser can't generate exactly 1 Hz steps. I don't
> know. You guys know more than me!

AT-cut TCXO vs. SC-cut OCXO maybe? A common diffrentiation.

Cheers,
Magnus