[time-nuts] Thunderbolt behaviour with long time constants.

[Mark Spencer]

Thanks for the comments.    I did a quick check of the noise floor of the 5370b while feeding the 10 mhz output of the tbolt to the start and stop inputs of the 5370b with a t connector. At a tau of 10 (approx 2.5 seconds) the Allan deviation is 1x10-11, at a tau of 100 (approx 25 seconds) it is 1 x 10-12.   Optimizing the trigger settings might lower this some what but I used the same settings as before.   I was not aware you need an instrument with a noise floor a couple of decades below the signals you are trying to measure.
Sent from my iPad

On 2011-02-09, at 9:19 AM, "WarrenS" <warrensjmail-one at yahoo.com> wrote
> Looks to be mostly a plot of the 5370B's noise floor at low taus.
> You may need something a couple of decades better if you want to measure the Tbolt at that tau setting.
> 
> BTW, You should NOT set the TBolt's TC to >999 sec. I  have found that the control can become somewhat unpredictable, AKA S/W bug.
> 
> ws
> 
> *********************
> ----- Original Message ----- From: "Mark Spencer" <mspencer12345 at yahoo.ca>
> To: <time-nuts at febo.com>
> Sent: Tuesday, February 08, 2011 7:48 PM
> Subject: [time-nuts] Thunderbolt behaviour with long time constants.
> 
> 
> First apologies for the zipped attachement.
> 
> I thought some members of the mailing list might find the attached plot of the
> performance of my Thunderbolt to be interesting. After looking at the
> performance of my Thunderbolt with a time constant of 225 seconds which seems to
> 
> be about right for my Thunderbolt, I noticed that the Allan deviation appeared
> to be be reduced at high values of Tau (approx 2,000 seconds..)
> 
> I then changed the time constant of my Thunderbolt to 2,000 seconds and compared
> 
> the two plots. I'm quite surprised at the result and the similarity between
> the peformance at low values of tau with the two different time constants.
> I took 4 readings per second with a 5370B, hence each unit of tau on the graph
> is approx .25 of a second.
> 
> I'll likley try other time constants in the future 
> 
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