[time-nuts] Secondary phase noise standard & FE405

Bob Camp kb8tq at n1k.org
Sat Nov 12 21:15:53 EST 2016


Hi

It depends both on the DDS “firmware” and the DAC linearity. You can play games to 
come up with the firmware side of it. The normal approach is to design the part so the 
DAC dominates. More or less, "more firmware bits”  is cheaper than improving the DAC. 

Bob

> On Nov 12, 2016, at 8:13 PM, Hal Murray <hmurray at megapathdsl.net> wrote:
> 
> 
> kb8tq at n1k.org said:
>> Yes, the FE-405 uses a DDS and a cleanup. Inside the cleanup loop the DDS
>> spurs come  straight through. Since the FE-405 compensates for all sorts of
>> things, the DDS moves around a lot. Even a one bit change on a DDS will move
>> spurs around. With an ever changing  DDS, you have an ever changing forest
>> of “stuff” on the output.  
> 
> Is there a web page or such telling me where the spurs will be on a DDS for a 
> particular constant?
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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