[time-nuts] OT Gel Cell question

Brooke Clarke brooke at pacific.net
Mon Jul 28 12:56:32 EDT 2014


Using lead acid batteries and a precision frequency standard is not a good thing if they are too close together.

A number of decades ago (before the Time Nuts or the internet) I was able to purchase a rack mount Gibbs 5 MHz double 
oven frequency standard that used a very nice Bliley glass tube crystal because it was not as precise as is was supposed 
to be.  It used GelCell backup batteries that were physically in the same rack chassis as the oven.  The fumes from the 
batteries when charging etched some traces off the PCB inside the oven defeating the temperature control but leaving the 
oscillator.  It took a long time to reverse engineer and repair it.  I've added a photo of the cord wood construction of 
the cylindrical oscillator.  The core of the cylinder holds the glass bottle crystal and the glass piston coarse tuning 
capacitor, surrounded by the first heater, circuitry for the oscillator and dual temperature control circuits on ring 
shaped boards.  These fit inside a cylindrical cavity which is the outer oven.  I've added a photo of the inner assembly 

Have Fun,

Brooke Clarke

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