> On Aug 16, 2015, at 6:04 PM, Bob Camp <[email protected]> wrote: > > Hi > > Here’s some of the “that depends” questions: > > What is your stability goal? > > You talk about the NIST numbers on GPSDO’s. What level of stability are you > after?
I believe I’m at or better than the stability I originally sought. Part 1 of my question is whether that’s actually true or whether my naivety is presenting me with a delusion. Part 2 is whether the price point at which I’ve arrived will support the level of stability I’ve achieved, or am I delusional in thinking people would or should pay what I’m asking for what I’m offering. > > What is your end application? > > Is this intended as a lab standard, the reference for a radio, something else > entirely? A low cost lab standard is what I have in mind. A box you can sit on your workbench with 3 BNC jacks that can feed 10 MHz into your frequency counter or what not. > > What is the destination? > > Is this heading towards a commercial venture or is it a basement project? I’ve entered it in the “Best Product” Hackaday 2015 prize contest. That said, I have no intention of attempting to compete with the established commercial firms in this space. I want to stay at around a Q:100 unit cost of around $75, which is where it is right now (the retail price is higher at the moment because I’m not manufacturing them in Q:100 lots yet). > > What is the budget? > > Do you have $200K to spend on this? Did the piggybank run dry at $100? > > What is the timeline? > > Does the project complete at the end of the summer, no matter what? Is it > something that is worth another year or two of effort? I’ve got something now, but I don’t mind revving it to improve it, as long as the budget doesn’t change a lot. A lot of suggestions so far have centered around improvements that could be made regardless of budget. Like I’ve said, I don’t want to try to compete with Trimble. > > What is your background? Mostly software, but in the last few years I’ve become reconnected to my nascent hardware side. I’ve been selling stuff in my Tindie store for a while now - a fairly eclectic mix of different projects that interest me. What led me to this project was another one - my Crazy Clock. I discovered a rather embarrassing design error that was causing errors on the order of dozens of ppm (I expected under ten). The first step in coming to grips with that issue was determining its scope, and that meant an extremely accurate low frequency counter, and that led me to needing a frequency standard. But I don’t have any way to test something I buy off eBay, so I wanted a GPSDO. But I couldn’t find any that weren’t way out of budget, so I set out to design one. And because I figured I wasn’t the only maker that needed something like this, but didn’t have the need or budget for something 2 orders of magnitude better, I thought I’d try this. Now where I am is trying to determine if I am correct in my assertions, and if my cost-benefit analysis of this as a product makes sense or not. > > Does all of the stuff we’ve been tossing around make perfect sense? (= you do > something like this for a living). Are we talking about a bunch of stuff that > makes > very little sense? (= you are just getting started at this sort of thing). No, it’s all perfectly sensible. > > Each of these twists and turns heads you off into a different set of further > issues and > likely some more questions. For a commercial venture, buying custom > oscillators in > bulk is a very normal thing to do. For a battery powered balloon carried > reference, you > do things different than for a rack mount standard. Each of these projects > people come up > with have its own unique drivers. > > Each of us in our replies, tries to guess what your constraints are or are > not. In doing > so we likely substitute our constraints for yours. The further our > constraints diverge from > your constraints, the further off base our advice and answers will be. I appreciate that. I came here with a narrow question in mind, but perhaps it wasn’t the correct one. > > Bob > > > >> On Aug 16, 2015, at 3:39 PM, Nick Sayer via time-nuts <[email protected]> >> wrote: >> >> >>> On Aug 16, 2015, at 12:31 PM, Tom Van Baak <[email protected]> wrote: >>> >>> Anyway, to answer your question -- to measure its true performance you only >>> need two things. 1) a phase meter (or time interval counter) that's good to >>> 1 ns or better, and 2) a local reference standard that's maybe 10x better >>> than the TCXO and the Adafruit GPS. Usually that means a cesium standard, >>> or supremely qualified GPSDO, or equivalent. >> >> I have a frequency counter, but it’s not a phase meter. I have a scope, but >> I assume that trying to use a ruler with scope traces isn’t the textbook way >> of doing that. :D >> >> I have considered in the past buying a used rubidium standard off eBay, but >> have hesitated because I don’t know how much life there is left in the tube, >> and I just have to take it on faith that it’s stable and accurate. I have >> somewhat more faith in the GPS PPS, but clearly that has limits. >> >>> >>> A number of us here on the time-nuts list have such equipment at home. And >>> unlike professional labs, we will do it for free/fun if you loan the GPSDO >>> for a week. >> >> I will happily *give* one to someone if they would be willing to help a >> relative newbie with this stuff. >> >> Just one though. They’re kind of expensive to build. :D >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
