[time-nuts] Dual Mixer/DMTD

Henk henk at deriesp.demon.nl
Fri Oct 2 14:11:08 UTC 2009

Hi Bert,

This is amazing and i hope that you can make it available for us to build
one. I am very interested.



> A couple of months ago I did announce that I plan to build a dual Mixer
> based on the NBS design with minor updates and add a counter section. All
> with
> a  cost goal of $ 200. Having all parts in house the goal has been reached
> when  boards get ordered in quantity ten. Thanks to inputs from Bruce
> Griffiths, Corby  Dawson and Richard McCorkle I do have prototypes and am
> in the
> testing phase.  Richard has written the code for the processors and the
> counter board is  assembled along with the simulator to be send this
> weekend to
> Richard to allow  him to test his code. The Dual Mixer will be assembled
> and
> tested this weekend  and will go next week to Corby to see how good it
> performs with his Maser and  compare to his NBS unit.
> What makes this unit different is that it has five counters running at
> 100
> MHz giving at 1 Hz a resolution of 1 part E 15. The counters talk through
> a
>  RS 232 interface to a computer. This will not only give Allan Variances
> but also  show the frequency difference with the same resolution at a 1 Hz
> rate or if  the offset Osc. is 10 Hz ten times a second. There are also
> outputs
> for  those that want to use their present counters for Allan Variance.
> Right now the  PC interface is RS 232 but long term I would like to see
> USB,
> because the  counter uses so little power it could be powered by the PC.
> Isolation to  the Dual Mixer is through high speed Opto couplers.
>  Long term I would like to encourage some one to design a two line
> display
> that shows Allan Variance and frequency difference and also records the
> information on a USB stick. That would allow total isolation from power
> since
> it  could run on one 12 Volt battery.
> What is next.
> Once Richard has checked his programs and Corby has checked the Dual Mixer
> I will incorporate any changes in the boards order and test one more set
> and  then make all information available to all. Richard has also
> graciously
> agreed to make his code available. In the meantime I have two extra boards
> and  part kits for some that are also willing to make a contribution to
> the
> project and I am not talking about money but further the project. Once
> finished  I will also have a few more kits available since with the
> exception of
> the  boards I purchase enough for ten units. The next board order (after
> check out)  will make it ten. I also have six HP 10811 that have been
> checked
> to 20 Hz  offset making them usable at 10 Hz offset at 5 MHz!
> If every thing works as planned, my goal is to have every thing released
> by
>  1 November. Cross your fingers.
> The Dual Mixer is 4.2" by 2.8" fitting into a standard German 72x111x20
> metal box for shielding. the counter is 4.8"x2.2".
> Bert Kehren
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