[time-nuts] DMTD Question

[EWKehren at aol.com]

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