Hi In this case it would need to be a really good oscillator at or very near 4 MHz. That's not a real common frequency. Yes you could double 10 MHz and then divide by 5, but that has it's own issues….. Bob On Sep 22, 2013, at 6:15 PM, Chris Albertson <albertson.chris@gmail.com> wrote: > On Sun, Sep 22, 2013 at 4:30 AM, W3KL <w3kl@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 > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.