[time-nuts] 10 MHz OCXO recommendations

EWKehren at aol.com EWKehren at aol.com
Tue Nov 11 07:00:14 EST 2014

It is not clear to me what your goal is. Simplicity, cost or performance. A 
 PLL based on 1 pps is not optimum.
I call this approach GPSPLL versus GPSDO. Thanks to work done by Karen in  
Moscow I found out that you can program a $14 ublox M7 to frequencies above 
1  KHz. If you use 200 KHz for 5 MHz XO and 400 KHz for 10 MHz you can make 
a GPS  PLL with one 390, one 86 and an op amp. If the XO output is sine wave 
you have  to add a Schmitt Trigger. I recommend Wenzel, AC14 or SN75176. I 
prefer 75176 it  is 8 pin DIL.
I do have a board layout if interested. Our Australian team members will  
introduce it to the HAM community. Not exactly a time nut product.
We have done a GPSPLL using a M7 at 1 KHz and tests show better than 1 E-10 
 at 1 second after 10 seconds GPS takes over it gets better following GPS  
performance. I have a few boards and op amps left over if interested contact 
me  off list. 
Bert Kehren
In a message dated 11/11/2014 1:05:49 A.M. Eastern Standard Time,  
jgray at zianet.com writes:

> You can  run at 400 KHz by dividing by 5/5 and 4/9.

True. Either will  work.

> You said "0.2ppm stability".  What do you need for  accuracy and/or how
are you going to calibrate your setup?

I will  initially calibrate the OXCO against my HP GPSDO. Idealy, it will
only need  checking against the GPSDO once a year. Is that asking too much
for it to  be stable over that length of time?

I could simply look up the specs  for the various models that I find on
ebay. However, I know that a lot of  the stuff that is sold has been through
the mill and may not meet spec any  more. Thus my request for
recommendations for models that someone here has  actually purchased and

Joe  Gray
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