[time-nuts] Thunderbolt & Lady Heather 48 hour precision survey

Rob Kimberley rk at timing-consultants.com
Sat Nov 27 10:33:23 UTC 2010


Comes down to the simple fact that it needs to know its position accurately
in order to give you good timing. I found this one out the hard way many
(many) years ago with an old single channel Trimble unit, where we had to
manually enter a known position in order to speed up acquisition. We were in
London at BBC Broadcasting House, and I inadvertently put the longitude of
the site East instead of West of Greenwich, and wondered why my 1PPS was
ramping off!

:-)

Cheers

Rob Kimberley

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Robert Darlington
Sent: 26 November 2010 6:41 AM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] Thunderbolt & Lady Heather 48 hour precision survey

For the last year I've been wondering why my thunderbolt doesn't perform as
well as I thought it should.  Now I know why (at least I think I know why).
I keep it in a styrofoam beer cooler surrounded with bottled water in a
draft free area and it's been all over the map.   I tried doing a 48 hour
survey through Lady Heather and it ended a few hours ago and there is now a
huge improvement in PPS stability -no more +/- 40ns excursions.  I'll be
keeping an eye on it for a bit but I think the survey helped significantly.
I'm almost sure I did a survey when I first got it but maybe I somehow
skipped over that.  Anyway, hope this helps somebody.

-Bob





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