[time-nuts] DMTD using Active Mixers

[EWKehren at aol.com]

It is 1 second and Corby uses his Maser, he has done many tests in the past 
 and he has an original NBS unit and is able to go back and forth. The 
system is  set up in such a way that you can also use .1 and .01 seconds.     
Bert
 
 
In a message dated 11/12/2009 6:58:02 A.M. Eastern Standard Time,  
mfsdlr at gmail.com writes:

Hi  Bert,

* The 2E-13 you talk about is ADEV at Tau = 1s, or...?

*  What kind of set-up you are using to measure it?

Thanks and best  regards,
Mario


On Thu, Nov 12, 2009 at 12:13 PM,  <EWKehren at aol.com> wrote:

> On our DMTD I am using Minicircuit  amplifiers and the SYPD-1 phase
> detector. Corby is presently testing  the unit and we see about 2 E -13. 
Let
> me
> stress again I am  not trying to push for the absolute best performance, 
my
> focus   is on simplicity, cost and ease to reproduce. The goal is 1 E -13.
>  Cost
> goal of  $ 200 has been achieved. That includes the five  channel counter
> where Richard  has finished the PIC programming  and modifications to the 
PC
> boards have been  implemented. Corby  is looking at what it will take to 
get
> to
> the   performance of the NBS unit, which is our baseline. I think this 
unit
>  will serve 99% of us well since it not only shows Alan Variance but
>  frequency
>  difference directly. Resolution is 1 E -15.
>  Bert Kehren
>
>
> In a message dated 11/12/2009 1:14:08 A.M.  Eastern Standard Time,
> magnus at rubidium.dyndns.org  writes:
>
> Bob Camp  wrote:
> > HI
>  >
> > I have no direct experience with the  Minicircuits  "active mixers", 
but I
> > have used some of their amplifier   chips. I suspect they use their own
> amps.
>
> Or at least  the same  amps.
>
> > The amps I worked with had  significant phase noise issues  when driven
> > within 6db of  their 1db compression point.  They  were "ok" at low 
drive
>  > levels. More or less then went from 3 db noise  figure to a > 20  db 
nf as
> > you went from -20 dbm to  0 dbm  output on a  +7 dbm amplifier.
>
> Uhm, that sounds more like distorsion   than noise. Anyway, if it is the
> same amps, then that would exclude  them  from being suitable for driving
> the mixer to saturation.  Thanks for the  report.
>
> Cheers,
>  Magnus
>
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