I once dated a girl who's father was a jeweler and had one of those
machines. He knew I was a ham and showed me how it worked. Its time base
was a tuning fork that was in a housing that looked like a can capacitor but
plugged in like a tube. I think the frequency was 400 Hz, known as cycles
in those days.
Regards.
Max. K 4 O DS.
----- Original Message -----
From: "Tim Shoppa" <tsho...@gmail.com>
To: "Tom Van Baak" <t...@leapsecond.com>; "Discussion of precise time and
frequency measurement" <time-nuts@febo.com>
Sent: Monday, February 10, 2014 2:01 PM
Subject: Re: [time-nuts] Line Frequency
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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