[time-nuts] Portable standard

Brooke Clarke brooke at pacific.net
Wed Apr 6 17:10:10 UTC 2011


Hi Joe:

Do NOT put the batteries near the OCXO!  Although you may get the 
advantage of thermal mass the problem with having acid fumes near copper 
traces on printed circuit boards will lead to trace etching.  Can you 
guess how I know this.
http://www.prc68.com/I/timefreq.shtml#Gibbs

Pulse (Burp) charging is not snake oil, although I thought it was until 
I saw it in action.
http://www.prc68.com/I/timefreq.shtml#Gibbs
http://www.prc68.com/I/PropelBB590.shtml
This was in relation to Ni-Cad and Ni-MH chemistry, so not sure how it 
works on lead acid.

Have Fun,

Brooke Clarke
http://www.PRC68.com


Joseph Gray wrote:
> If I were to buy an HP 10811A OCXO to use as a portable, battery
> powered frequency standard, how would you recommend that it be powered
> and packaged? Assume that the final package would be powered 24/7 and
> sitting on a shelf most of the time. Prior to portable use, it would
> be checked against my GPSDO. Portable use would probably be at worse a
> few days, but more likely less than a day.
>
> I'm thinking of using a couple of 12V, 7AH SLA batteries and float
> charging them. Some charge circuits use pulsing current for SLA
> batteries. Would this affect the OCXO?
>
> Obviously too much air flow will be a problem. Can the OCXO, batteries
> and associated circuitry be sealed in a box with no vent holes (not
> strictly air tight)? What about putting the OCXO in a small styrofoam
> box by itself? Will that cause overheating or other issues? How about
> vent holes in the overall enclosure and baffles around the OCXO to
> minimize air flow?
>
> Should I forget the whole idea and just buy a rubidium?
>
> Joe Gray
> W5JG
>
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