[time-nuts] need recomendation for a portable 10mhz referenceoscilator

SAIDJACK at aol.com SAIDJACK at aol.com
Wed Dec 12 17:36:37 EST 2007

In a message dated 12/12/2007 14:11:50 Pacific Standard Time,  
rmoncur at bigpond.net.au writes:

>Now  I am not sure which of any of the above points are necessary  or
>important but I would be grateful for the thoughts of  others.

>Regards Rex VK7MO

Hi Rex,
that's a lot of great information! Since you are not too concerned about  
overall frequency accuracy (I assume 1 to 5E-09 would be acceptable) you may not  
need to or want to lock to GPS at all. With a typical OCXO retrace of 5E-09 
you  would have a (fairly stable) frequency offset of 235Hz or so at 47GHz.
As you mentioned your requirement to be ~2Hz deviation at 47GHz this  
calculates to about 4.3E-011 stability over 46 seconds.
GPS itself cannot deliver that, but a good OCXO flywheel will do that. Any  
GPSDO with ADEV better than 5E-011 should be sufficient locked to GPS or not,  
but you may have to keep the oven on at all times as you said.
Tom measured the Fury's ADEV (double oven) to achieve this performance  above 
measurement intervals of 0.01 seconds already so that should work really  
well, and in this short time frame (46 seconds) it's pretty much all up to the  
OCXO (aging and tempco correction by the processor should not be a factor at 
46s  intervals either).
Thus a good MTI double oven OCXO should do the trick for you and GPS  locking 
is not really needed, except maybe for getting initial frequency  accuracy.
The advantage of this is that a typical MTI Eurocan double-oven OCXO  
consumes only about 1.7W and can thus be safely and easily powered by a car  battery.

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