[time-nuts] What is the BEST crystal?

[Bruce Griffiths]

Interferogram showing vibration nodes etc for quartz ring resonator frequency standard attached.

Bruce
> On 01 March 2020 at 14:27 Bob kb8tq <kb8tq at n1k.org> wrote:
> 
> 
> Hi
> 
> It’s also the size of the 2.5 MHz 5th’s and similar parts made “way back”. They went into glass packages 
> the size of door knobs. Packaging / design / mounting / processing has changed a lot since then. 
> 
> Bob
> 
> > On Feb 29, 2020, at 7:41 PM, John Moran, Scawby Design <john at scawbydesign.co.uk> wrote:
> > 
> > Wow, that provoked an interesting discussion!
> > 
> > Thanks for all the information and references to further information - it should keep me quiet for a while.
> > 
> > Interestingly 50mm diameter was about the diameter of the crystals used by the British Post Office in the early days for generating a master oscillator. It wasn't ground into a plano-convex lens but as a ring and was about 10mm thick. Like the old WW2 crystals the electrodes weren't plated but just contact rings. I have no idea what frequency they were ... by the time that I realised they were scrapping all this kit it was gone and I only managed to salvage two GPO Type 36 master 1S pendulums from a dumpster!
> > 
> > Thanks again for all the feedback.
> > 
> > John
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> 
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