[time-nuts] Re Tbolt tuning (was re 10811 foam enclosure)

Mark Spencer mspencer12345 at yahoo.ca
Mon Jan 10 02:09:10 UTC 2011

Interesting thanks.  At the moment my Tbolt board (I just have a bare board 
without an enclosure) seems to work best with a 400 to 600 second TC and  
damping in the range of .7 to 1.   I'm thinking mounting it in a heavy metal 
enclosure may improve things and allow the use of longer TC's.   
I can frequently see the Tbolt reporting changes in the 1pps timing due to 
satellite changes, that don't show up on the 5370, so I suspect I've reached the 
point where some of the short term noise is being filtered out.  

Changes reported by the Tbolt in the 1pps timing due to temperature changes do 
tend to show up on the 5370.
 I've only just gotten the 5370 figured out and interfaced to a computer so I 
can log the data systematically.

----- Original Message ----
From: WarrenS <warrensjmail-one at yahoo.com>
To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
Sent: Sun, January 9, 2011 12:59:40 PM
Subject: Re: [time-nuts] 10811 foam enclosure

A simple box is fine for many Tbolt applications.

Much depends on the TBolt Osc and what setting you have, especially the TC and 
With the factory default setting you can pretty much put the thing in an outside 
unsheltered shed and have it work OK,
But it will not be the best it can be.
The object is to slow the frequency control loop down as much as possible so it 
does not transfer the short term GPS noise to the osc.
The slower the temperature changes the less the loop has to work and the higher 
the TC can be set.

Do the same test with the Tbolt's TC set to 1000 seconds, damping to 1.2 and 
watch the phase error using Lady Heater.
You'll see BIG BIG differences based on the rate of change of the temperature.



Mark Spencer mspencer12345 at yahoo.ca  wrote:

My experiences placing my thunderbolt board in various insulated containers show 
little or no improvement over simply putting a cardboard box over it to keep 
drafts away.  As time allows I'm going to re run some of the tests using my 5370 
and an external standard vs relying on the data from the thunderbolt itself but 
I'm not expecting to see any significant changes.

I've also started to run some tests with disciplining turned off on the 
thunderbolt and the drift of the ocxo is quite apparent.

I'll likely get a heavy die cast box for my thunderbolt at some point.

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