[time-nuts] Did a member of time-nuts buy this?
timenuts at binsamp.e4ward.com
Wed Dec 10 23:12:03 EST 2014
>> 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
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
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?
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