[time-nuts] How To Measure Long Term Phase Stability Of An Oscillator

Chris Albertson albertson.chris at gmail.com
Sun Sep 22 18:15:39 EDT 2013


On Sun, Sep 22, 2013 at 4:30 AM, W3KL <w3kl at w3kl.com> wrote:
> How does one make a measurement of the phase stability of an oscillator over
> a time period much larger than the oscillator period?  For example, I have
> an oscillator with a frequency of 4 MHz and I want to measure the phase
> drift of the RF between a given point in time and then a time 4 seconds
> later.  I want to make a measurement that has a precision of 0.1 degree or
> better.

The simplest way to first to get a very much better oscillator than
the one you need to test.  You need a "refference".   Then you "add
them" and if there is any deference at all you will get a beat
frequency

If the two are "close" the beat will be very slow, slow enough you can
measure the period with a wrst watch.   Put the two on a daul channel
scope nd watch.

More sofesticaed method is to use a transformer to add the two signals
then feed the sun into a computer's audio input or otherwise record
the beat frequency.   You can do an FFT on the recording.

I sure others will have even better methods but my point is that
simple technique can work, provided you have a really god reference
oscillator.

-- 

Chris Albertson
Redondo Beach, California


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