[time-nuts] DMTD Question

David C. Partridge david.partridge at dsl.pipex.com
Mon Jan 25 13:43:48 UTC 2010


Translation: FWIW == For What It's Worth

So,  one hundred boards will probably cost only a little more than ten
boards.

Dave

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of EWKehren at aol.com
Sent: 25 January 2010 13:27
To: time-nuts at febo.com
Subject: Re: [time-nuts] DMTD Question

I am not familiar with FWIW 100. Tell me more.  Thanks    Bert Kehren
 
 
In a message dated 1/25/2010 8:22:30 A.M. Eastern Standard Time,
david.partridge at dsl.pipex.com writes:

FWIW 100  boards will likely cost not a great deal more (say $5-20 depending
on board  size than ten. 

Dave
-----Original Message-----
From:  time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of  EWKehren at aol.com
Sent: 25 January 2010 12:01
To:  time-nuts at febo.com
Subject: [time-nuts] DMTD Question

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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