[time-nuts] The VE2ZAZ GPSDO

[Dave Brown]

Well said, Randy.
 It wasn't my intention when I asked for comments to trash anybody or 
anything. In the somewhat 'rarefied atmosphere' of this forum I doubt 
that any comments made were intended to be anything other than 
objective.

 I guess the ultimate question is whether or not the claimed 
performance objective can be met with the hardware/firmware detailed 
in the article, regardless of some of the apparent shortcomings 
already noted.   If the answer is yes, then I believe the discussion 
here should be interpreted as no more than suggested improvements that 
could be implemented.

Regards
DaveB, NZ



----- Original Message ----- 
From: "Randy Warner" <Randy at synergy-gps.com>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Sunday, October 22, 2006 9:35 AM
Subject: Re: [time-nuts] The VE2ZAZ GPSDO


> Said et al,
>
> Although everything said in this thread is accurate, I guess I find
> myself a little reluctant to just trash the author and the project 
> out
> of hand. He is obviously a hobbyist without a lot of precision 
> timing
> theory in his back pocket (hey, I'll place myself in that category, 
> I
> learn more everytime one of you guys posts to the list).
>
> Does the project have problems and limitations? Absolutely. Will the
> 7805 and ripple counters create problems over temp? Certainly. Will 
> they
> drift enough to cause problems for the author during use at fairly
> constant room temperatures in his HAM shack? Probably not enough to 
> be
> noticeable.
>
> Does the project perform "well enough" for the author and other
> hobbyists that will enjoy building one for themselves? Absolutely.
>
> On the GPS side of things, we sell a LOT of nav receivers for timing
> applications. If you are designing a product that is cost sensitive 
> and
> doesn't need ns accuracy or TRAIM functions of an M12M-T, a Sony GXB
> receiver will cost you about half as much and still hold the 1PPS 
> within
> 50nS (1 sigma). Even though is is a nav receiver it's 1PPS 
> performance
> is equal to the old UT+ timing receiver.
>
> Sorry for the rant. It's been a long week ;-)
>
> Randy
> ________________________________________________________________________
> _________________________________
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] 
> On
> Behalf Of SAIDJACK at aol.com
> Sent: Friday, October 20, 2006 11:30 PM
> To: time-nuts at febo.com
> Subject: Re: [time-nuts] The VE2ZAZ GPSDO
>
>
>
> Hello Bruce,
>
> I agree. The DAC reference is an LM7805CT regulator with 0.8mV/C 
> (typ.)
> temperature coefficient. Considering that typical Oscillators  (MTI
> units for
> example) have about +-20Hz deviation per 5V - this alone  - 
> excluding
> the Opamps tempco, would lead to a temperature drift  of 0.32Hz over 
> a
> 50 Deg C temp range. That's about 3.2E-08, quite  a bit worse than a
> good surplus oscillator.
>
> And the 7805 does not have a maximum tempco rating, so it could be 
> 10x
> worse than that...
>
> bye,
> Said
>
>
>
>
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