[time-nuts] Thunderbolt? (re simple gpsdo.)

Mark Spencer mspencer12345 at yahoo.ca
Fri Dec 30 14:13:41 EST 2011

On a related note is anyone aware of PC controlled (Ie. RS232 or maybe GPIB ?) DAC's that would be suitable for this type of application ?   

I've also contemplated simply using the DAC of a TBolt but it would seem to be waste of a Tbolt.  I'm thinking along the lines of something that might acquired used on an auction site.

--- On Fri, 12/30/11, Hal Murray <hmurray at megapathdsl.net> wrote:

> From: Hal Murray <hmurray at megapathdsl.net>
> Subject: Re: [time-nuts] Thunderbolt? (re simple gpsdo.)
> To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
> Received: Friday, December 30, 2011, 1:16 PM
> > "What is the simplest design for a GPSDO that uses
> only the PPS signal from
> > a modern GPS?" 
> Some sort of oscillator with a voltage control.
> CPU with a timer/counter that can capture the PPS.
> DAC.
> Software.
> Drive the CPU from the osc so you can count cycles between
> PPS pulses.  Use 
> the DAC to adjust the frequency.  Build a low pass
> filter in software.
> The DAC may be the tricky part.  You would like lots
> of bits, but it also has 
> to be stable.
> With a given DAC, you can get finer control by trading off
> range.
> -- 
> These are my opinions, not necessarily my employer's. 
> I hate spam.
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