[time-nuts] Man with too many clocks.
paul.alfille at gmail.com
Thu Nov 3 21:07:42 EDT 2016
By the way, the HP5370B has a OCXO, not TCXO. It needs a while to become
stable, but should be quite consistent after that.
On Thu, Nov 3, 2016 at 4:50 PM, Nick Sayer via time-nuts <time-nuts at febo.com
> I’m going to try and describe my thoughts, but it may not come out as
> “right” as some others here can do. Still…
> One problem you’re going to run into if you go down the road of attempting
> to PLL one thing to another is that you have to find a balance between
> phase control and frequency stability.
> You’re going to always be reacting to the phase drift of your disciplined
> device. Your “knob” for doing so is to adjust (probably in steps) the
> frequency. If your PLL is very “twitchy,” then you’re going to move that
> knob very quickly and firmly, resulting in very tight phase control, but a
> frequency that, at least over a short term, will jump around a bit.
> By contrast, if you are very reluctant to move the “knob,” then you’re
> going to move it so slowly that by the time you have a meaningful effect on
> the phase, the phase will have drifted quite a bit. That said, your
> movement of the frequency knob will be so slow that the frequency stability
> would be much better, at least over the short term.
> In essence, this is choosing the PLL time constant. How you do so depends
> on the behavior of your device as well as the stability you desire from the
> > On Nov 3, 2016, at 5:20 AM, Peter Reilley <preilley_454 at comcast.net>
> > I am the proverbial man with too many clocks and I don't know what time
> it is.
> > To correct this situation I have decided to calibrate everything.
> > I have a HP 5370B, a HP 6370A, and a HP 5328A all with the TCXO option.
> I also
> > have some TCXO modules. I figured that I would calibrate them against
> my Trimble
> > Resolution T GPS receiver.
> > I put the 1 PPS signal in one channel of my scope and one of the 10 MHz
> > signals in the other channel and look at the phase relationship. The
> TCXO's are
> > already close enough that I should not be out by more than a fraction of
> a waveform.
> > I understand that I have to deal with the 1 PPS without sawtooth
> > I expected to see the 10 MHz signal bounce around but not move more than
> > of a wave length. Instead I see the 10 MHz waveform appear steady for
> a few seconds
> > then jump a significant portion of the wave. The jump is too much to
> be confident
> > that I have not slipped one cycle.
> > Can I do what I am trying to do or am I missing something?
> > Pete.
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