bryan (11/30/82)
All power companies in the continental US , except in Texas,
are connected together in a power-grid. The frequency of this
grid is continuously checked with WWV time. Therefore the absolute
maximum variation from 60hz is +/- .003% at any time, and is
typically kept within +/- .01%. The frequency can be a low of
59.98hz or a high of 60.02hz (long term accuracy is much better).
Also there is little fluttering from 59.98 to 60.02, any correction
in frequency takes a little time to do (when you consider the mass
of a power station generator).
Concerning the gadget that has a crystal osc. to maintain
a constant 60hz. If you take a 600khz X-cut crystal with a TC of
-20ppm per degree, and increase the temperature 10 degrees it will
osc. at 599.8khz.. Unless this gadget has a crystal oven to maintain
a constant temperature it will probably deviate more from 60hz than
line AC. Also consider the effects of drift, unless it is on all of
the time.
Why don't turntables today use good ole sync. motors?
1). It ain't fashionable.
2). The problem of changing speeds (33 to 45 to 78).
3). Having to use two different drives, one for the US
and one for Europe.
4). DC motors allow the adding of some bells and whistles:
SPEED ADJUSTMENT and a STROB LIGHT.
P.S. I ment to say .033% not .003%
ihlpb!bryan
Bryan Delaney
BTL Naperville,ILL