[time-nuts] TBolt

[Pieter Ibelings]

Hi,

Where can I purchase one or two of the time-nuts Tbolt specials?

Thanks,

Pieter


----- Original Message ----- 
From: "John Ackermann N8UR" <jra at febo.com>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Saturday, August 09, 2008 4:27 PM
Subject: [time-nuts] TBolt and Z3801A performance data


>I just put the results of some tests of 2 "Time-Nuts Special"
> Thunderbolts, as well as 2 Z3801As, at
> http://www.febo.com/pages/gpsdo_comparison/
>
> I learned an interesting (and important) lesson in doing these
> measurement.  I initially measured the pairs of GPSDO against each other
> (e.g., one TBolt as "reference" and the other TBolt as "DUT").  In
> theory, if the two oscillators are identical, and if their noise is
> uncorrelated, the results of the pair can be used to deduce the results
> of the individual units.
>
> However, in this case doing so gave a very optimistic view -- the TBolts
> were better than the pair of Z3801As!  Another set of measurements
> comparing the GPSDOs against an independent reference revealed that the
> first measurement was a lie.
>
> I guess you can think of it like this.  Picture two OCXOs that both age
> at the same rate and in the same direction.  Because they drift
> together, measuring their relative phase hides their actual drift and
> makes them look better than they are.  On the other hand, if they were
> drifting in opposite directions, they would look worse than they are.
> An identical aging trend is a "correlation" even though it's external to
> the things we usually think of.
>
> John
>
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