[time-nuts] Line Frequency

Tim Shoppa tshoppa at gmail.com
Mon Feb 10 15:01:21 EST 2014


>  IIRC some watch or clock company had a patent on calibrating a
wristwatch crystal against AC hum. I read it once but can't find it now.
Can you hunt for it?

Tom - when I was a kid in the 1970's, before digital watches, the local
jeweler had device with a table on which a watch or clock could be placed,
the table must've been a microphone, and it had a pen recorder. It produced
a chart that looks like the "phase data" charts on yours and other
websites; the jeweler adjusted the clock so the recorded line had no slope.
It had a selector for several common watch/clock gear ratios (don't think
it did the tuning fork watches like the Accutron; I think there was a
similar but different device for checking the tuning fork Accutrons, my dad
was enough of a clock nut that he actually had a tuning fork Accutron, and
he is a NAWCC member still!). Over the course of an hour the adjustment
could be fine trimmed to the point where we knew the movement was good to a
few minutes a month. Don't know if it was locked to mains frequency or had
a crystal. Do you know what this was called?

Tim N3QE



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