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

[SAIDJACK at aol.com]

In a message dated 12/11/2007 11:41:02 Pacific Standard Time,  
eric.fort at gmail.com writes:

>I'm  looking for a fairly basic, relatively simple 10 Mhz PORTABLE
>reference  (probably quartz based) with enough stability over a period
>of a week  of outdoor temp extremes to keep a 47Ghz transmitter locked
>within  100hz  while mountaintop contesting.  Suggestions  are
>appreciated.  something that is small and ran off 12 volts dc  (car
>battery) would be a definite  plus.

>Thanks,

>Eric


Hi Eric,
 
if my math is correct, you will need about 26.3 microseconds holdover  
performance per day to achieve that requirement.
 
A good (and well-aged) double-oven OCXO with aging compensation should be  
able to provide that type of performance. The problem is: how much physical  
movement will the unit experience? What are the temperature extremes that are  
expected, and how fast does the ambient move between the temp extremes? Can it  
be GPS locked during that time?
 
Our Fury double-oven OCXO GPSDO may be a bit expensive for this  application, 
but if you can keep it within the 0C to 70C temperature range of  the OCXO 
(by proper thermal shielding) then it would fulfill all of  your needs.
 
The electronics themselves are rated to operate down to -20C, so only the  
OCXO needs attention to be well shielded thermally so as to keep it  
self-heating at a comfortable temperature.
 
Aging in holdover is typically better than 7 microseconds per day at room  
temp, and it runs from a Lead Acid car battery, all the way down to 11.0V.
 
If you can use a GPS antenna, the performance would be better than your  
requirement of course.
 
Expect it to draw about 5W, depending on temperature, so a typical 80Ah  
battery (derated for low temperature to say 40Ah) would last about 40Ah/0.45A =  
3.7 days to 7.4 days depending on the performance of the Pb battery. But you  
should really use a marine deep-discharge battery, your car batt may die when  
deep-discharged, especially at low temp.
 
At low temperatures Pb batt's have much lower voltage than at room temp, so  
you will need to be able to go down to <12.0V.
 
A small solar array (2W to 5W) and a bit of sun may extend that  operating 
time significantly.
 
bye,
Said



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