[time-nuts] Dual Mixer/DMTD

[EWKehren at aol.com]

Henk, it will be available to every one the challenge will be buying in  
groups, I definitely do not want to be in the mail order business.   Bert
 
 
In a message dated 10/2/2009 10:11:49 A.M. Eastern Daylight Time,  
henk at deriesp.demon.nl writes:

Hi  Bert,

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

regards,

Henk

>  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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