[time-nuts] GPS Phase locked Local Oscillator experiment
Magnus Danielson
cfmd at bredband.net
Thu Mar 8 23:40:59 UTC 2007
From: Peter Schmelcher <nebula at telus.net>
Subject: Re: [time-nuts] GPS Phase locked Local Oscillator experiment
Date: Thu, 08 Mar 2007 10:55:29 -0800
Message-ID: <5.2.1.1.2.20070308095745.02b9e358 at pop.telus.net>
>
> >Wonder how the Z3816A would like a modified VP inside... Hmmm... a closed
> >loop system, what are really the timeconstants relevant, to make sure it
> >is stable?
>
> That is where I am going. The UT+ oncore inside the Z3816A is a simple
> crystal and easy to feed with the 3325A. I currently have an ongoing oven
> turning point experiment with the MTI oscillator or I would have done it
> already. The frequency of the local oscillator will need to be different by
> 0.5 Hz I think. The pps pulse needs to jump back and forth by 1 clock cycle
> for the pps pulse to have any feedback information in it when the local
> oscillator is phase locked unless the Z3816A reads the sawtooth residual
> from the internal UT+.
If you have a smaller offset, you get a better dither-curve (a sawtooth) rather
than a square-wave. Your 3325A has _no_ problem at all doing that. :)
Also, I would run the 3325A from one of your Rubidiums.
> >The big difference is that Peter used another GPS clock as reference. By that
> >he is actually doing a delta measurement between the receivers. Hooking the
> >3325 up to a Cesium would be a much more interesting measurement.
>
> I have measured the stability of the Z3616A 10MHz output indirectly by
> measuring a good ovenized crystal oscillator in the past it is less than
> 50uHz rms with 10 samples of 1.8 seconds. For comparison my two rubidium
> oscillators are about 200 to 350 uHz rms. The HP engineers did a good job.
Indeed.
> >You would like to query the receiver in a different maner, so that would
> >require a modified firmware.
>
> My data logging is not what it should be. I do not know a simple way to log
> the sawtooth data to a file so I did a screen capture.
It should be a fairly short script to do it. :)
Personally I fancy real programs (in C).
Cheers,
Magnus
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