[time-nuts] Re: Rb Standards C-fields

[Bob Camp]

Hi

What is the goal? 

Temperature stability will always be a limiting factor in any of this.

The control signal is only supplying part of the C field current. The “rest of it” is coming from devices internal to the package. 

Bob

> On Aug 22, 2023, at 1:50 AM, Bob Stewart via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> Is there someplace I could get some practical information about C-fields in Rb standards?  I'm not looking for the physics of how they work.  What I need is on the practical side.  This relates to the AT&T RFG-RB unit I bought.  Looking at the components, I don't see any obvious voltage references.  It has a couple of power supply chips, but nothing better than an LM-340T-5 or whatever it was.  And the C-field adjustment is a 10-turn 5K pot.  
> My bottom line question is this:  Would it would make any real difference to the stability of the 10MHz output if I were to add an external voltage reference chip, such as an ADR4550A (or B or C) and a 25-turn pot, or even a DAC1220-E and a dsPIC33 to run it?  I'm assuming the center C-field voltage is 2.5V.  Given all the electronics in the thing, I'm tempted to just pull both boards out and make a new board to support the Rb oscillator with just the features I need.  But if the thing is already near the limits of the Rb oscillator there's no point.  It contains an Efratom 102100-003, for which I can't find any information.
> 
> Bob
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