[time-nuts] Dual Mixer

EWKehren at aol.com EWKehren at aol.com
Tue May 11 14:02:32 UTC 2010

The Dual Mixer project is nearing completion.
Let me refresh every ones memory as to my goals.
a)  Total cost less than $ 200
b)  1 E-13 with a one second offset
c)  use parts attainable by every one 
d)  easy to assemble only a few surface mount parts
e)  a five channel counter that yields 1 E 15 resolution and  interfaces 
directly to a PC via  RS232 or USB
f)   A counter that also gives you instant frequency  difference at the 
sample rate, not only Allan Variance
g)  Modular so one can use only the Dual Mixer
h)  Modular so one can use multiple units to do simultaneous  comparison of 
more than two oscillators.
i)   Isolation between D/M and counter so that the counter can be  powered 
by the PC USB port 
I am happy to report that all goals have been accomplished, attached is a  
picture of the D/M, limitation of the file size does not allow me to attach 
an  actual board picture, but if you contact me direct I will send you one, 
the  final board is actually nicer since the first layout had to accommodate 
several  variances.
The D/M part leans heavy on the original NIST unit with a few substitutions 
 and recommendations from Bob Camp. Also beside Opto Couplers SN65LVDS1's 
have  been included for those that want to use other counting methods. 
Selection of  filter capacitors allow the use at other offset frequencies such as 
10 and 100  Hz. The D/M fits in a standard 74 X 111 X 20 mm Euro case and 
the counter can be  stacked below or next to it using the Opto Isolators as 
the inter connect. The  SYPD-1's fit right on the board but connections are 
included to use the HP 10514  A. As a matter of fact removing the HP mixer 
board from its housing   fits it nicely on the board and every thing is still 
inside the housing.
The counter will handle 1 an 10 Hz offset with a 1 E 14 resolution at 10  
Hz. Thanks to Richard Mc Corkle we have great drawings and code, available to 
 every one.
Code, drawings, list of material and PC board layouts and its  file, will 
be available to every one once the project is completed.
I need help in the following areas
a)  help me create a nice set of drawings that are computer generated  
something I am not able to do
b) create the computer program that takes the output of the counter board  
and allows Allan Variance plots, frequency difference and dual temperature  
readings and plots using RS232 and USB.
c) an independent test by a third party.
As I said previously, I am not getting in the business of supplying parts  
but will work with people that will help achieve the three points listed 
above.  Presently I have boards on order and will have two uncommitted board 
sets and  probably also component kits.
Please contact me directly. 
Again thank you Corby Dawson, Richard Mc Corkle and Bob Camp.
Bert Kehren   Miami
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