[time-nuts] Performance verification for time counters

Bob kb8tq kb8tq at n1k.org
Wed Nov 29 17:56:24 EST 2017


There are a number of ways to build a synthesizer that do not involve a modern
DDS architecture. The gotcha with a DDS in this case are the sawtooth spurs. To
get them down to the 5 ps level, you would need a DDS with a clock that is well into
the 100’s of GHz.


> On Nov 29, 2017, at 5:47 PM, Chris Caudle <chris at chriscaudle.org> wrote:
> On Wed, November 29, 2017 3:51 pm, Poul-Henning Kamp wrote:
>> While it is tempting and probably easiest to use a DDS style
>> generator, I recommend a synthesized one instead, to avoid
>> trouble with numeric spurs.
> Can you describe the distinction you are making between a synthesized
> generator, and a direct-digital synthesized generator?  I do not
> understand what would be meant by a synthesizer which is not DDS.
>> The HP3336 with its outstanding level-control is a much
>> overlooked bargain for this kind of stuff.
> I looked for the manual, and it seems to have ROM feeding values to a DAC.
> Is that not DDS?
> -- 
> Chris Caudle
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