To follow up on yesterday’s post, here’s a similar TCXO oscillator which is considerably more accurate:
It’s a 10.000 MHz unit which has been calibrated and claims a 0.1 ppm accuracy. That’s 10 MHz ± 1 Hz, i.e. 7 digits. Here’s the output signal, which appears to be AC coupled:
Not bad for a low-cost unit. I got it from the RFcandy shop. Current consumption is 0.94 mA @ 5V.
Once you start looking into this stuff, all sorts of things pop up on the web. There’s a group of amateurs who call themselves Time-Nuts (terrific name!) and who aim to keep track of time as accurately as they can – with pretty amazing results. In a comment yesterday, John Beale pointed me to a web page with info about the Rubidium clocks now available cheaply on eBay.
I found this page most entertaining, summarizing the history of accurate time-keeping in a few slides.