[time-nuts] Where to get Winchester connections for Efratom FRK?

[Magnus Danielson]

From: Rex <rexa at sonic.net>
Subject: Re: [time-nuts] Where to get Winchester connections for Efratom FRK?
Date: Fri, 23 Nov 2007 00:41:07 -0800
Message-ID: <47469223.4020808 at sonic.net>

> swingbyte wrote:
> > As an aside, what resolution counter is needed to calibrate the FRK?  Hp 
> > 5328? HP 5370?
> >
> >   
> That's kind of an open-ended question. You don't actually need a 
> counter, you need a source that is known to be at least as accurate as 
> you want to set the FRK. One question is: do you really have a need for 
> a level of accuracy that you are trying to work toward? The group, in 
> general, tries to go towards "because it is there" challenges in 
> accuracy, stability, and phase noise. It isn't required by everyone.

Let me add that you need some sufficient resolution to acheive the intended
resolution over reasnoble time. While a GPS receiver may have some jitter, it
should be sufficiently stable (unless you made some very bad decissions on
antenna position - maximum sky view please). One common method is to measure
the time interval between the reference PPS and the rubidium PPS (you can
divide it down using TTL divider chain). You log the TI values over time and
time-nuts take pride in processing it for stability using Allan deviation
plots (which show the low frequency noise process levels) but you may be more
interested in the pure frequency error. You should be able to cancel most of
the frequency error so that the accumulated phase drift in the TI data for
longer runs is almost completely canceled. Large frequency errors is pretty
easy, but as you fine-tune it, the noise processes makes it hard to directly
compare as you will not be able to directly separate low frequency noise from
linear phase drift, i.e. frequency error. This is why it can be handy to
actually do the Allan deviation plot.

There are many ways to use a GPS and some counter. The principle remains the
same, the counter is the tool to analyze the difference between the reference
and the device under test. The counter has the resolution, noise process and
non-linearities low enought and the reference the stability and precission
enought for a particular DUT requirement.

Cheers,
Magnus