[time-nuts] GPS receiver local oscillator (was: 1PPS for the beginner)

[Wayne Holder]

> Hene we would need a DAC resolution of 1e-4 or 14bit. That's already a
DAC that has a price
> tag, multiple times that of the TCXO.

 I'm not sure what you consider "low cost' but a 16 bit DAC like the
MAX5216BGUA+
<https://www.mouser.com/ProductDetail/Maxim-Integrated/MAX5216BGUA%2b?qs=sGAEpiMZZMswix2y39ylddFcA27kRSR8c6%2fDlE45lrQ%3d>
goes for $3.40, quantity one.

Wayne


On Tue, Aug 14, 2018 at 2:33 PM, Attila Kinali <attila at kinali.ch> wrote:

> On Tue, 14 Aug 2018 11:05:17 -0400
> Bob kb8tq <kb8tq at n1k.org> wrote:
>
> > > Is there a need to make the math easier?
> > > This is what we have microprocessors for.
> >
> > There is *always* a need to make the math easier if I’m quickly typing
> up an example. For proof I
> > reference the hundreds of posts in the archives where I didn’t quite get
> it right :)
>
> I am pretty sure that the math is less the problem than being able
> to control the oscillator precisely enough while staying at low cost.
>
> The average TCVCXO has a tuning range of...let's say 10ppm = 1e-5
> over a range of 0-3V. Now, we want to be able to shift the phase
> such, that we are within 1ns at the next pulse (actually we want it
> to be better, but lets keep the numbers simple). This means we need
> to control the frequency with a precision of 1e-9. Hene we would need
> a DAC resolution of 1e-4 or 14bit. That's already a DAC that has a price
> tag, multiple times that of the TCXO. Hence it's cheaper just to
> shift the frequency/phase digitally and not touch the TCXO.
>
>
>                         Attila Kinali
> --
> It is upon moral qualities that a society is ultimately founded. All
> the prosperity and technological sophistication in the world is of no
> use without that foundation.
>                  -- Miss Matheson, The Diamond Age, Neal Stephenson
>
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