[time-nuts] FE-5680A Mechanical Question

EWKehren at aol.com EWKehren at aol.com
Fri Jan 13 17:19:18 EST 2012


Are we not overdoing it. 7E-13 for $15 KISS, and if you want to go beyond  
that use a $ 30 analog version.
Looking right now at 1 E -14, I do se temperature influences, with my heat  
sink stable to .1 C. Mainly due to the fact that is only one side of the 
unit  and it is clearly designed to use all sides for heat dissipation.
 
Bert Kehren
 
 
In a message dated 1/13/2012 5:02:48 P.M. Eastern Standard Time,  
lists at rtty.us writes:

Hi

What we are talking about is toggling the least  significant bit in the DDS 
to achieve a resolution of less than that LSB. It  could be done to a set 
period (like a PWM) or pseudo  randomly to reduce  the noise signature. 
Either way, roughly a 16 element long "period" should be  quite adequate. 
7x10^-16 / 16 would give us a 4x10^-14 step and a 2x10^-14 max  error.

Bob

On Jan 13, 2012, at 4:30 PM, Don Latham  wrote:

> Oh, I hate to be a pedant, but are we talking about  dithering, that is
> random perturbations to remove things like  hysteresis, or using the
> finite steps as a bang-bang servo?
>  Don
> 
> Charles P. Steinmetz
>> Bert wrote:
>>  
>>> wrong there is no DAC involved, it is a DDS
>>  
>> Ahh.  Not so simple, then.  I still don't much like the  notion of
>> dithering, but it may be the only alternative.  Or,  as has also been
>> suggested here, add a manual C-field adjustment  (but that would not
>> change the fact that the RS-232 adjustments  would still be ~ 7e-13
>> steps).
>> 
>> Best  regards,
>> 
>> Charles
>> 
>>  
>> 
>> 
>> 
>> 
>> 
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> 
> 
> -- 
>  "Neither the voice of authority nor the weight of reason and argument
>  are as significant as experiment, for thence comes quiet to the mind."
>  R. Bacon
> "If you don't know what it is, don't poke it."
> Ghost  in the Shell
> 
> 
> Dr. Don Latham AJ7LL
> Six Mile  Systems LLP
> 17850 Six Mile Road
> POB 134
> Huson, MT,  59846
> VOX 406-626-4304
> www.lightningforensics.com
>  www.sixmilesystems.com
> 
> 
> 
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