Hi Bob, > or 1x10^-8 per volt. If it’s a 10 MHz OCXO. > That would be 1x10^-14 per uV > 4.7 x 10^-13 for 47 uV Good, so I'm not out to lunch here. ;) Thanks for verifying those numbers for me!
> What makes you believe that the OCXO’s temperature performance it not the issue? Because I can blow a hair dryer on it, and make very warm - almost hot to the touch and not see the phase or DAC change. Yet 2 degree thermal cycles in the room show up in the DAC and phase. I'm pretty sure it's not the OCXO, but if you know anything that would suggest otherwise, please do share. > I’d guess that the analog stuff is much better than it needs to be. At this point I would tend to agree, but don't have hard numbers to know for sure yet. > Subject: Re: [time-nuts] Linear voltage regulator hints... --> WHY? > Ok, so why am I harping on the “need” for all this from a system standpoint ? I have no idea. > 1) Adding stuff to a design that does not make it measurably better is simply a waste of money. That’s ok if it’s your money. The stuff added needed to be added. It fixed an understood problem/limitation in the current hardware. It did make the system 'measurably' better. > 2) Others read these threads and decide “maybe I need to do that..”. Now it’s a waste of somebody else’s money. If someone makes the decision to spec their part based on a somewhat random email, from some random thread, from an email list, they fully deserve the spend the extra $6 on parts. It serves them right for being so foolish! (Serously?!?) > 3) Still others look at this and decide “If I need to do that, I’m not even going to start”. That’s not good either. This isn't extremely hard, but it is challenging. Maybe someone wanting to build a GPSDO should know what they're getting into. If a 10e-6/DegC scares them, you'd think coefficients of "1x10^-14 per uV" would be worse. > 4) Analysis *is* part of the design process. It should very much be part of this. It is. It's how the analog portion got to where it is now. What makes you think it isn't? > 5) Focusing on a design aspect “because I can” is a very common thing. I do it all the time :) Because I fall into the trap often, I recognize just how much time gets soaked up on dead ends this way. I'm doing this "because it's what I can easily contribute to the project". I'm spending considerable resources in terms of time and expenses studying and improving a piece of hardware to help a guy out, and to learn something along the way. > 6) There are very real issues when doing this. Sorting out what’s real and what isn’t is far from easy. The more “noise” in with the signal, the less likely others are to figure out a good approach. Huh? Do you mean this particular response to the thread? Going back to the original post, the reason for the question was to look for a lower cost yet suitable replacement for the 'roll your own' design. One that could be shotgunned into the prototype to look for the thermal drift that is evident, and is not coming from the OCXO. This is part of the analysis you so eloquently spoke about above. As it turns out there are no parts that good. Moving foreword with the project, the COTS parts don't cut it, so at this point I see no other choice than to build something. You obviously have a lot of experience in this field. I'm glad that people like yourself are willing to share with the rest of us. But, please don't assume I'm incapable of navigating the cost vs. performance curve for a project, or that I'm incapable of determining if a part is over specified. It's insulting that you think so. Thanks, Dan _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.