[time-nuts] Method for comparing oscillators

[J. L. Trantham]

I have done this and I am not sure I can tell the 'direction of rotation'.
I can easily tell if it reverses but once going, I can't tell which
direction.

Joe

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of J. Forster
Sent: Monday, August 03, 2009 11:14 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Method for comparing oscillators


Rather than using a scope in Y-T mode (with triggered sweep) I find that
using a scope in X-Y mode makes it much easier to compare frequencies. Doing
this, you essentially get a synchroscope display. If the two waveforms are
sinusoidal, the trace will be a circle, the rate of revolution is the
frequency difference, the direction of rotation tells you which frequency is
high/low.

FWIW,
-John

=======

> John,
>
[snip]
> Your oscilloscope method (without proper handling of phase 
> ambiguities) measures a compound of both properties and is not well 
> suited for stability measurements. [snip


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