[time-nuts] Thunderbolt Question

[Hal Murray]

wa6rzw at comcast.net said:
> I have been using a surplus Thunderbolt for about six months, and it seemed to
> be working  fine.  In January 2012, a message came up in yellow, (LEAP
> PENDING!), I don't know what this means, but since it didn't go away on Feb 28,
> must not be leap year related.  About a week ago I got a Holdover: xx secs,
> message.  It was a new figure in yellow.  Yesterday the Thunderbolt stopped
> working correctly, there were no satellites found.  I tried Lady Heather, and
> Trimble Studio without success.    I finally got the unit back in service with
> a program called "Tboltmon.exe".  After it was running for a couple of hours I
> restarted Lady Heather.  This morning I again have "Holdover: 50 secs".

> Does it sound normal, or is this unit headed for the junk box?

I didn't see anything that you said that sounds unreasonable.

There is a leap second scheduled for the end of June 2012.  That info gets 
distributed via GPS.  The TBolt will pass it on to client software.  I don't 
remember the details, but you can find them if you look in the TBolt software 
data sheet.

There is a quirk with NTP.  It also has a mechanism for distributing 
leap-pending info.  The catch is that it assumes the leap will be at the end of 
the current month.  (I hacked a Jun/Dec filter into the HP/Z3801A driver because 
it screwed up the last time we had a leap second.  That seemed easier to test 
and less likely to be buggy than trying to decode the actual time of the next 
leap second.)  I should go check the TBolt code.


On the holdover...

Holdover just means that you can't see any good-enough satellites.  (You only 
need one for timekeeping.)

How good is your antenna location?  Were you watching to see if it was going 
into holdover before?

My antenna setup is poor.  My TBolt goes into holdover several times a day, more 
on a bad day, maybe none on a good day.  That's great for testing software, not 
so good for providing a super-clean time or frequency reference.

How many times and/or how long it stays in holdover depends upon ???  (I don't 
know.)  It may depend on the phasing of the GPS satellites.  It may depend on 
the weather and/or the amount of water in/on my roof and/or the local trees.  (I 
have a big pine tree to the south/southeast.)



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