[time-nuts] Quantic GPS receiver EFC control (was: Papers on timing for lunar laser ranging)

Attila Kinali attila at kinali.ch
Mon Jul 17 17:17:00 EDT 2017

On Mon, 17 Jul 2017 10:24:42 -0700
Brooke Clarke <brooke at pacific.net> wrote:

> The Quantic Timing GPS receiver makes use of patent 5440313
> which results in a 48 bit DAC.  How does this idea compare?
> http://www.prc68.com/I/Q5200.shtml
> https://www.google.com/patents/US5440313
> PS the above patent cites 4582434 i.e. the Heathkit GC1000 HFDO.

Figure 4 is nothing but an elaborate way of describing a PWM generator.
Figure 5 uses an DDS to generate an offset frequency relative to the
GPSDO output and uses that to phase lock the GPSDO to an external
frequency reference .

I don't think that Fig 5 gives any advantage over a proper DAC.
If anything, I would guess the spurs of the DDS generate a lot
of noise on the EFC. It's advantage is, though, that you can lock
the 10MHz on any reference that is close to 10MHz (or far off, for
that matter) and use the stability of that reference for the output
of the GPSDO.

There are IMHO better ways to achieve that, though.

				Attila Kinali

You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering.  -- The Doctor

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