[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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