[time-nuts] What is the BEST crystal?

[John Moran, Scawby Design]

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