[time-nuts] Man with too many clocks.
preilley_454 at comcast.net
Thu Nov 3 21:23:03 EDT 2016
Yes you are correct. All of the devices I am working with have OCXO's,
it was a type
or a brain short.
On 11/3/2016 9:07 PM, Paul Alfille wrote:
> 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?
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