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" <[EMAIL PROTECTED]> To: "Discussion of precise time and frequency measurement" <time-nuts@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: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] > On > Behalf Of [EMAIL PROTECTED] > Sent: Friday, October 20, 2006 11:30 PM > To: time-nuts@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 > > > > > _______________________________________________ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > _______________________________________________ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > > > -- > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.1.408 / Virus Database: 268.13.9/490 - Release Date: > 20/10/2006 > -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.408 / Virus Database: 268.13.9/490 - Release Date: 20/10/2006 _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
