[time-nuts] DMTD using Active Mixers

EWKehren at aol.com EWKehren at aol.com
Thu Nov 12 11:13:11 UTC 2009


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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