[time-nuts] DMTD using Active Mixers

[Mario Sanchez]

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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