[time-nuts] DMTD Question
EWKehren at aol.com
EWKehren at aol.com
Mon Jan 25 13:56:39 UTC 2010
Bob, the mixer/Filter op amp schematic is a direct copy of the NBS unit
with late model op amps, comparator and an opto coupler in stead of the
transformer. Isolation amps are actually MINI CIRCUITS the next version will be
op amps. I will ask Richard to release the counter schematic. Since there
are still changes I am reluctant to release partials.
Once a final version is complete, schematicsand PC board layouts will be
available to every one, to do with as they choose.
If you contact me directly I will send you a picture.
Bert
In a message dated 1/25/2010 7:54:09 A.M. Eastern Standard Time,
lists at cq.nu writes:
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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