[time-nuts] Dumb question about SC-cut crystals

[Magnus Danielson]

From: "Rick Karlquist" <richard at karlquist.com>
Subject: Re: [time-nuts] Dumb question about SC-cut crystals
Date: Mon, 22 Oct 2007 14:32:51 -0700 (PDT)
Message-ID: <10280.192.25.142.225.1193088771.squirrel at webmail.sonic.net>

> ); SAEximRunCond expanded to false
> Errors-To: time-nuts-bounces+magnus=rubidium.dyndns.org at febo.com RETRY
> 
> A lot of work has been done in this area under the
> designator "Microprocessor Controlled Crystal Oscillator"
> MCXO, which is probably not a really great name.
> Anyway, they are non ovenized and use SC cuts.  I believe
> the original FCS paper on them was around 1990.

I found the use of the different tempco dependence of the 1st and 3rd modes
an interesting way of measuring the temperature-dependent shift. By having a
dual-mode oscillator setup and then mix the 1st mode frequency with the divided
down version of the 3rd and then measure the beat-frequency. This can then be
used in various ways such as resynthesis etc. It's in a long presentation of
Vig. He shows a number variants of this scheme. I am not yeat convinced it is
the best of methods, but for smaller volume oscillators it is certainly an
interesting approach.

Cheers,
Magnus