[time-nuts] EFC divider resistors

[Bob Camp]

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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