[time-nuts] EFC divider resistors

[Tom Knox]

I am not sure if anyone else mentioned this, Placing the parts against the oscillator with a little thermal epoxy under a small piece of foam so they are at least partially "ovenized" should really help. 

Thomas Knox



> From: lists at rtty.us
> Date: Fri, 31 Jan 2014 22:36:46 -0500
> To: lajeunesse at mail.com; time-nuts at febo.com
> Subject: Re: [time-nuts] EFC divider resistors
> 
> Hi
> 
> If you attenuate the DAC 100:1 to 1000:1 before it hits the OCXO, the DAC does not matter much. That may sound like a crazy ratio, but it is indeed possible with some of these OCXO EFC ranges. They can have a *lot* of swing. 
> 
> The reference is an LTZ1000, they run about $50 in single piece lots. You can get resistors that run below 1 ppm tracking without a whole lot of effort 
> 
> Bob
> 
> On Jan 31, 2014, at 8:38 PM, Robert LaJeunesse <rlajeunesse at sbcglobal.net> wrote:
> 
> > Must be military prices. If using 5 PPM resistors in the build a reference much better than that isn't needed, especially if the temperature is somewhat controlled, like time nuts do. A commercial 3 PPM/C part, the LM4140A, is $4.54 each in singles. At 2.2uV p-p it's reasonably quiet as well.
> > 
> > Considering stability influences, what provides the DAC reference? That's rather important as well. 
> > 
> > Bob LaJeunesse
> > 
> > I'd also note the 2 PPM ratio tracking dividers, the MAX549x series, can be had in the $3.49 range, also not all that expensive.
> > 
> > 
> > 
> >> ________________________________
> >> From: Bob Camp <lists at rtty.us>
> >> To: Bob Stewart <bob at evoria.net>; Discussion of precise time and frequency measurement <time-nuts at febo.com> 
> >> Sent: Friday, January 31, 2014 7:17 PM
> >> Subject: Re: [time-nuts] EFC divider resistors
> >> 
> >> 
> >> 
> >> ... A good voltage reference will set you back about $50 or so. 
> >> 
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