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Article #9442Re: Getting timing from line cycles (was Re: Sidereal Time Clock)
From: Paul Bame
Date: Tue, 08 Jan 1991 20:38
Date: Tue, 08 Jan 1991 20:38
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1538 bytes
> From what I understand, using the 60Hz line as a reference for timing is not > a good practice if you want any accuracy. Interesting article in '73 magazine this month about using TV horizontal sync as a frequency standard. Seems the networks use expensive, stable and accurate sources to generate their (nationwide) timebase. The '73 circuit uses an inductive coupling to a TV to grab the sync and then a PLL-based circuit to turn it into a useful frequency. This could be adapted to the sidereal clock problem. You can also use the colorburst but it requires connection to the TV. Note, that local cable companies may re-generate colorburst and/or Hsync of dubious accuracy. Satellite and air-wave reception seems like the best chance for a stable source. Also note that local material (read: commercials) inserted by affiliates may be of dubious accuracy. The article mentions (I think) that PBS is a good choice. -Paul "Spice is the Variety of Life" bame@hpfcbig.sde.hp.com N0KCL
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arc1-ca.pugleaf.net!utzoo!censor!geac!torsqnt!lethe!yunexus!ists!helios.physics.utoronto.ca!news-server.csri.toronto.edu!cs.utexas.edu!samsung!usc!elroy.jpl.nasa.gov!sdd.hp.com!hplabs!hpfcso!hpfcbig!bameReferences:
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Path: arc1-ca.pugleaf.net!utzoo!censor!geac!torsqnt!lethe!yunexus!ists!helios.physics.utoronto.ca!news-server.csri.toronto.edu!cs.utexas.edu!samsung!usc!elroy.jpl.nasa.gov!sdd.hp.com!hplabs!hpfcso!hpfcbig!bame From: bame@hpfcbig.SDE.HP.COM (Paul Bame) Newsgroups: sci.electronics Subject: Re: Getting timing from line cycles (was Re: Sidereal Time Clock) Message-ID: <6560004@hpfcbig.SDE.HP.COM> Date: 8 Jan 91 20:38:42 GMT References: <1990Dec13.043046.14036@zoo.toronto.edu> Organization: HP SESD, Fort Collins, CO Lines: 19