[time-nuts] DMTD Question

Bob Camp lists at cq.nu
Mon Jan 25 12:53:55 UTC 2010


Hi

I think you will find that the SYPD-1 (or RPD-1) is the better choice compared to the SRA-1.

Are the schematics out there for the curious to look at?

Thanks!

Bob


On Jan 25, 2010, at 7:01 AM, EWKehren at aol.com wrote:

> Allow me to add some comments to this subject.
> Five month ago I set out to make a DMTD that would be $ 200 max and be such 
> that any one can build it with readily available parts. The unit also 
> includes  five counters yielding a resolution of 1 E-15. Using five counters not 
> only  gives Allan Variance but also frequency difference. The counter is 
> powered by  the computer through USB and also transfers the data to the PC. 
> The counter  section is less than $30 of the total cost. The cost goal has 
> been  reached. The counter does not have to be used if one wants to use his 
> present  counter. The DM board does have high speed opto couplers that allow 
> other  counters. Corby is presently using that approach. Cost does not include 
> the  offset Osc. but a low cost solution is in the works, subject to  
> evaluation.
> Corby Dawson and Richard McCorkle have been major contributors.
> The goal is 1 E-13 and present tests show 3 E-13 right out of the box. 
> Having Cesiums, Rubidiums and Xtal Osc. the best I have is a FTS 1000  
> A-100 with 3.11 E-13 at one second. I also think I will never have any  thing 
> better than the FTS unit. That is why my goal is 1 E-13.
> The present unit uses SYPD-1 as mixers but Corby will test the unit  with a 
> couple of HP10514A's to evaluate the Mixer contribution.
> I realize I am offending some of the purists on this site but I wanted to  
> keep cost down so I squeezed both channels on a very compact board  
> (4.3X2.9) and the counter is on a 4.3X2.3 board. How ever if we will  not reach 1 
> E-13 with this approach I have a fallback using individual  boards for each 
> channel still meeting the cost goal. Other Mixers will also be  evaluated, 
> like the SRA1 since price and availability of the HP10514A/B will not  help the 
> cost goal.
> 1 E-13 should satisfy 95% of time-nuts and at $200 including PC  boards. 
> The second board with some changes hopefully will be assembled this week  for 
> testing and based on its results a third board will go  to ExpressPCB. 
> It is moving slower than what I had hoped for, but 3 E-13 right out of the  
> box with no special magnetic shielding or power supply decoupling gives me  
> hope.
> PC boards will be the major cost factor, for my calculations I assume in my 
> calculations that ten boards will be ordered at a time.
> 
> Bert Kehren   Miami
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