Hi Without some qualifier on "how good", we all will be talking about hourglasses and cesium standards at the same time. That makes sorting things out a bit difficult. It may get you into building a "controlled hourglass" that's less accurate than a free running $10 wrist watch.
So far the only suggestion of a "how good" has been TBolt performance. At least that's how this started out. Building a "cpu only" GPSDO can be done with a big enough chip. If you are limited to clip leads to wire it up, the cost advantage over a TBolt may not be there. That makes the issue of significant performance loss a very real issue. -------------------------- Just as surplus deals on TBolts come and go, so do deals on OCXO's and GPS's. Do I price the OCXO at the $13 that I once saw it for, or the $70 that they sell for today? Is the GPS in the junk box (that I paid $200 for) free because it's sitting there? Let's not even wonder if any of the stuff works... For the sake of moving this forward, I'll suggest that half the fair cost of a (working) TBolt is the OCXO and the GPS. Put another way, your $200 (or what ever) is split $100 for the OCXO plus GPS and $100 for: 1) The nice shielded case it's all in 2) The connectors 3) The onboard power regulation and filtering 4) The communications in and out of it 5) The 10 MHz and PPS buffering and generation 6) The PC board it's all built on 7) Putting it all together 8) Programming all the parts in there 9) Testing it and troubleshooting it 10) The smarts to get it to do what it does I'm sure we could spend at least a year splitting hairs on that division of costs :) To "win" the hourglass vs cesium fair trade proposition you need to come up with a gizmo that: 1) Does 1-10 above 2) Works with just a GPS and OCXO added. 3) Costs less than $100 4) Works as well as a TBolt 5) Has a Lady Heather like monitor program to go with it For the sake of eliminating crazy GPS cards. Let's say you also need a source where we can buy both the OCXO and GPS used for less than $100. If you want to factor in lower performance, I'll grant a waver for the fact that you can average multiple gizmos and the result will get better by the square root of the number of gizmos. If it's half as good as a $200 TBolt it needs to be 1/4 the price. Bob -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Jim Lux Sent: Friday, December 07, 2012 10:13 AM To: time-nuts@febo.com Subject: Re: [time-nuts] GPSDO Alternatives (GLUE) On 12/6/12 5:01 PM, Bob Camp wrote: > Hi > > The solution to the problem is well known in several forms. Cost is below $5 for pretty much all of them. No need to re-invent the wheel. The gotcha is that you can't do it 100% with internal CPU peripherals. You will need *some* glue. > > I think that's the interesting aspect of this discussion (because it mirrors many similar such discussions I've had over the years).. The challenge is not in building a GPSDO.. there's tons of ways to do that at minimal hardware cost.. The challenge is "how do you do it without using any additional glue logic or hardware" That is, given things you can buy off the shelf, and no hardware work other than fabricating cables or soldering a wire or two, what can you do inexpensively. _______________________________________________ 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. _______________________________________________ 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.