[time-nuts] Time interval measurement vs dual mixer method

Bob kb8tq kb8tq at n1k.org
Sat Jan 20 08:26:23 EST 2018


Hi

The quality of the offset signal source matters in a DMTD system. If you are using
a “noisy” source you will have trouble with the data. You also will have trouble if the
offset signal is correlated in some way to one of the DUT signals. 

Bob

> On Jan 20, 2018, at 3:43 AM, timeok at timeok.it wrote:
> 
> 
>   Hi Corby,
>   I did several tests to verify the system noise floor using the same source for both input channels. I have seen that the result varies a lot as the difference in time between the two channels varies.
>   Moreover, if I do two successive tests without  changing the parameters and the duts, the result can not be superimposed.
>   It may be that I make a mistake or do not take any parameter into account.
>   I also wonder if there is any commercial realization of the DMTD system.
>   Cheers,
>   Luciano
> 
> 
>   Da "time-nuts" time-nuts-bounces at febo.com
>   A time-nuts at febo.com
>   Cc
>   Data Thu, 18 Jan 2018 11:13:54 -0800
>   Oggetto [time-nuts] Time interval measurement vs dual mixer method
>   Luciano,
> 
>   Not sure what you mean by "two measures made on the same DUT never
>   coincide".
> 
>   The plotter program takes out wraps which since your phase gain is so
>   large are due to happen.
> 
>   For lower Tau measurements just adjust the phase for close to equal and
>   run shorter plots.
> 
>   These can be spliced into the longer Tau plot.
> 
>   I routinely get repeatable plots on the same DUT with my DMTD setup.
> 
>   Careful setup and understanding what you can and cannot accomplish is the
>   key.
> 
>   Cheers,
> 
>   Corby
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