[Elecraft] Rb & GPS DO comparison

[George Dubovsky]

Hi Brian,

If you want to go straight to the top of the frequency measuring heap, I
have a GPS-disciplined Rubidium for sale ;-)  It's a NIB Symmetricom StarLoc
II Plus, that gives you GPS accuracy when it's locked to the sats, and
Rubidium accuracy when it's in holdover.

I've been a ham long enough to remember when I was happy to know that I was
inside the band!

73,

geo - n4ua

On Wed, Jul 20, 2011 at 2:52 PM, Ken Alexander <k.alexander at rogers.com>wrote:

> Hi Brian,
>
> Interesting post.  I've read of others using GPS this way, but what does
> this kind of accuracy buy you when maybe 1 in 100,000 other hams go to this
> kind of trouble?
>
> 73,
>
> Ken Alexander
> VE3HLS
>
>
> --- On Wed, 7/20/11, Brian Alsop <alsopb at nc.rr.com> wrote:
>
> > From: Brian Alsop <alsopb at nc.rr.com>
> > Subject: [Elecraft] Rb & GPS DO comparison
> > To: elecraft at mailman.qth.net
> > Date: Wednesday, July 20, 2011, 2:41 PM
> > Guys,
> >
> > This may be of some use to those interested in locking the
> > K3 to an
> > external source.  The issue of what kind of source to
> > used has been the
> > subject of a number of postings.
> >
> > Clifton labs did the above comparison. Jack's Rb standard
> > came in at
> > about .0004 Hz relative to a GPS DO at 10MHz.
> >
> > I was wondering how accurate the EBAY purchased LPRO-101
> > Rubidium
> > oscillator was.  (I wanted to use it as a master
> > oscillator for my test
> > equipment and perhaps later the K3.)
> >
> > Comparisons to WWV indicated that in all liklihood it was
> > well within 1
> > Hz.  There was no way to determine if it drifted
> > within that range.
> >
> > Curiosity finally got the best of me.  I purchased an
> > EBAY Trimble
> > Thunderbolt GSP Disciplined oscillator.  Supposedly,
> > it is more accurate
> > than the Rb secondary standard. Assuming it's truth, the Rb
> > secondary
> > standard was evaluated via the phase drift method using a
> > dual channel
> > scope.
> >
> > Out of the box, the Rb standard came in at 0.0075 Hz (10
> > MHz) of the
> > GPS-D0. With a little tweaking of the ten turn pot in the
> > LPRO-101, the
> > two are well within 0.001 Hz (nominally 0.0008Hz) at
> > 10MHz.  There is a
> > small drift component of 0.0002Hz after 3 hours after lock.
> > Tweaking
> > isn't straight forward.  The appears to be a few
> > minute latency period
> > after a tweak.  One can't simply stop the phase angle
> > from moving by
> > turning the pot.  Doing so results in an over
> > correction a few minutes
> > later.
> >
> > It's difficult to tweak the Rb standard beyond this degree
> > of accuracy.
> >   It takes more than 20 minutes to determine a data
> > point.  To do better
> > would take some automation and a phase detector running for
> > several days
> > to get sufficient statistics.  Next project is
> > building a phase
> > detector.....
> >
> > I'm pleased.  The Rb standard has lots of
> > advantages:  Price, minutes to
> > locking on, portability and simplicity.
> >
> > The next question: How accurate is the
> > GPS-DO?   Anybody got a hydrogen
> > maser handy?
> >
> > Now what to do with the GPS-DO?
> >
> > Remember when decent receiver dials had only 5 KHz
> > markings?
> >
> > 73 de Brian/K3KO
> >
> >
> >
> >
> >
> >
> > -----
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> > Date: 07/20/11
> >
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