From: "Michael A. Terrell"
Subject: Re: Better than 2ppm TCXO for <$25?
Date: Mon, 28 Oct 2002 19:18:52 -0500
Organization: Have you seen my bench? No, really! Where is it?
X-Mailer: Mozilla 4.61 [en]C-CCK-MCD (Win95; U)
> "Chris Carlen" wrote in message
> > Hi folks:
> > I also am aware that one could use other methods, like interfacing to a
> > radio controlled clock, GPS, the internet time RFC, etc. Those things
> > are very interesting, but I'd like to have a clock on my desk before the
> > end of the decade. Even with a basic Xtal, that will be a challenge for
> > my slow-going self.
> Actually, it might be worth your while to consider WWV. There are chips
> available from several suppliers that perform virtually all of the clock
> functions. The frequencies used are around 60kHz. I don't recall that
> interfacing them would have been very difficult, although our application
> didn't require a time display.
> I used to have a list of the part vendors, but have long since lost it. On
> the other hand, I don't remember them being too difficult to track down (I'm
> sure I googled). It's worth a quick look, even if you decide to go with
> something else.
> As an aside, if you're after long term accuracy, specs like 2ppm don't
> really provide enough information. Clock errors accumulate over time, and in
> general white noise effects will dominate in the short term, and low
> frequency noise effects will dominate in the long term. Short and long term
> are somewhat subjective, and depend on the type of clock. In high
> performance frequency standards, low frequency effects may not become
> apparent for days or weeks. The point is that although you might be
> expecting an accuracy of 2 seconds every 11.6 days (1 million seconds), you
> may find that your actual clock performance is significantly worse. On the
> other hand, if you compared your clock to a reference standard over a
> relatively short time period (say, less than an hour), it might be
> significantly better than 2ppm.
> -- Mike --
Michael A. Terrell