[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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