>> It would appear the best approach is to simply start reading the >> posts at the beginning and save the interesting ones. > >There are lots of interesting threads on Time Nuts ...
Yes. It is very easy to get distracted. >>> First step is to be able to extract timing data from individual >>> sat's. Not all GPS modules do this correctly. > >> Can you tell me some of the ones that do? > >I have yet to see one for under $2K that does it correctly. I don't >have the cash to buy ones at those sort of prices. Some have >reported that the old Motorola UT's will do it. The samples I have >tried have not done very well. I may have not had them running right >- who knows. OK, that pretty much eliminates the NIST data. >>> 5) Feed that into your control loop equation. >> There's another term I need to research! >It's not a simple control process, but it's not all that terrible >either. It just takes a bit of work to optimize. Figure a few months >to a few years for the optimization depending on what you have for >issues along the way. >> OK, so I figure out how to do this. How do I tell if this is >> making the gpsdo more accurate? In other words, how do I get the >> ADEV without having an H-Maser? >You get a Cs (or other atomic standard) or you compare several >different GPSDO's against each other. The preference would be for >groups of three so you can rule out ones that are not doing what >they should. I see the issues people have here getting their cs to work. Maybe the best approach is different gpsdos in a N-corner hat. I have already bought stuff in groups of 3 to prepare - gps receivers, rubidium and morion oscillators, a trimble, etc. >You also need the measurement gear to resolve frequency down in the >1x10^-13 range. A normal counter will not do that. Yes, I have a new invention for a DMTD that may work. >Backing off a bit - why do this? >You can buy commercial GPSDO's on eBay. Yes, I also see the difficulties some have here trying to get them to run or even talk to them. >You can build published GPSDO designs that are known to work. Yes, I have seen most of them. I think I can do better. >What is the objective here? I'm retired, kids are married, wife moved back to France, and I have no girlfriend or interest in getting one. I have a small pension so I can afford to buy parts and pcbs. I have been involved in precision instrumentation since 1960 and have a few patents and some new inventions I think could be applied to time and frequency applications. There are many new dacs, op amps, and bipolar microwave devices that offer much lower noise than current designs use. I think the performance can be improved in some areas with new components and design techniques, and I have equipment and time to explore. As usual, I will have to build much of my own test equipment to measure the improvements, but I have been doing that for 5 decades so I'm used to the idea. Some of the items may be good enough to start a new company and bring to market. So I can call it R&D and get tax benefits. Most of all, it's an interesting challenge. Lots to learn, many new ideas and concepts, and a ready source of information in the archives and online. What could be better? >Bob Thanks, Mike _______________________________________________ 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.
