[time-nuts] EFC info on Trimble 34310-T OXCO

EWKehren at aol.com EWKehren at aol.com
Sat Aug 23 16:23:34 EDT 2014


Charles 
I was also not aware that James Miller had done a Shera, I have copied his  
other unit I call a GPS PLL and my notes show a Clark but they are the 
same.  What I added was a op amp in the filter to drive low impedance OCXO 
inputs and  we use a $ 15 ublox M7. at 1 KHz. Right out of the box we get 1 E-10 
using a  Morion and I am turning it over to some Hams to play with the 
filter. It was  more of a test what can be done with a very low cost simple 
circuit and not  intended for time nuts. Would be the wrong direction.
As to Ed's and Bob's comments our projects are not able to compete with  
commercial products and I do not think that should be our goals. Having spend  
extensive time on temperature control, I limit my self to 10 C and use fans 
on  all Rb's and passive on OCXO's. Concern about vibration induced noise 
on the  OCXO made me remove the fan on the tbolt. Added a lot of mass and now 
ordered  some foam balls from China to fill the enclosure as some one 
recommended.  Foam has to be close cell so not to absorb moisture. Did also run 
some foam  pieces through a mixer with mixed results. Decided to wait for the 
small balls  and do moisture tests on both and fill a tbolt. Since I have 
two identical units  I will be able to compare..Goal is to slow the 
temperature change to a rate that  the GPSDO loop takes care of the frequency change. 
Bert Kehren
 
 
In a message dated 8/23/2014 3:42:24 P.M. Eastern Daylight Time,  
csteinmetz at yandex.com writes:

Ed  wrote:

>I don't think you're correct about the Miller GPSDO  containing a 
>Shera controller.

Is there more than one "Miller  GPSDO"?  I was referring to this one, 
by James Miller G3RUH, which  uses a Shera controller and 10811  OCXO:

<http://www.jrmiller.demon.co.uk/projects/freqstd/frqstd.htm>

Answering  my own question: yes, there appear to be at least two 
"Miller GPSDOs,"  both by the same Miller.  Here is another 
(presumably the one Ed was  referring  to):

<http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm>

Best  regards,

Charles



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