[time-nuts] GPS Phase locked Local Oscillator experiment

[Magnus Danielson]

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