Hi There are a number of GPSDO’s on the market. For less than the price of a working 5071, you can probably buy a couple dozen of them. In terms of long term accuracy, a GPSDO will beat a Cs. Most of them (but not all of them) will do as well as a “standard tube” based Cs at short(er) tau’s. Compared to a system locked to an LF signal, a modern GPSDO is *way* better.
Downsides include the need to mount an antenna with a good sky view. Keeping them on power all the time may or may not be a downside. You can indeed build one up and do it that way. When a “pre built / tested / working” device is as cheap as they are, there is not a big need to do that. Bob > On Feb 3, 2019, at 7:04 PM, Christoph Kopetzky <c...@cksd.de> wrote: > > Hi Bob and time-nuts, > > thank you for your infos. It seems not to be an easy job to get a used cesium > clock in a good shape > with some reserve for a good few years of lamp live and an adaquate price. > The ones on the market are either for parts or like the both examples at > ...bay fakes which costs > a lot of money and the not so experienced users are getting into a bigger lot > of problems... > > The other crux with this clocks is oviously that they need to let them > running all the time for reaching > the better stability and exactness what the should have as as a reference in > the lab. > > Bob your pricing info for an exchange of the cesium tube seems to be not the > right direction for the hobby > electronics user like me. I think it is a good idea not to buy such a clock > at the moment. > > But the problem of mine and my be a lot of electronic developer and > scientists is that they cannot have their > reference systems running all the time. It must be possible to build a > reference which does not need weeks > to reach its best exactness and stability within hours... > > Is there a known solution available which allows good short time stability > and also exactness which will be reached > within a maximum of one hour after power on? > > My thoughts are going into the world of the well known GPSDOs with a good > OCXO inside and a precise Timing GPS receiver > module like UBlox NEO-M8P or a Furuno GT-87xx, a high precision roof antenna > with a good view of the sky, and one of > the best rubidium oscillators such a SRS PRS10... > This combination must do the trick. It should be not to hard to feed the pps > signal from the GPS receiver into the PRS10. > I read that the developer from SRS implemented the regulation software loop > for that into the firmware of the Rubidium > oscillator. With saving the states of the gps and the rubidium in two > separate real time clocks (battery buffered) and a > few lines of software for the microcontroller to arrange all with a display > must be enough. > > I would be lucky if you guys could give me some tips about that or > alternatives to get such a stable reference with a short > avalability timeframe for locking and stabilisating. > > Are there may be ready useable open hardware sources available? > > Thank you guys in advance for all your help... > > -- > with best Regards > > Chris > > Am 03.02.2019 um 23:34 schrieb Bob kb8tq: >> Hi >> >> The gotcha with a Cs is the tubes wear out. Last time I put a tube in a 5071 >> it cost just >> about $40,000 including custom shipping of the “hazardous” Cs. From the >> description >> on that uint it does not *appear* that things are working correctly. >> >> Even if you do get a working Cs standard, the question is - how much longer >> will the >> tube last? It might be good for another 10 years. It might die tomorrow. >> That tends to be >> a bit of a concern as far as running them all the time in a basement lab. >> >> With the high performance tubes in the 5071, my experience was that 6 to 7 >> years of >> continuous use was about it. The “standard” tubes in the 5071 should be good >> for > 2X that >> time period. >> >> None of this is to say that the *only* reason one fails is the tube. It is >> not at all uncommon >> to have other stuff fail. Usually the small stuff gets fixed and they go >> back into service. >> When the tubes go (or the problem is complicated) the go on the market….. >> >> Indeed none of this is to say you *can’t* get a working Cs. You most >> certainly can. This >> list is one pretty good place to find a working one from somebody who >> *knows* that it is >> running properly. I’m not selling any of mine, but you may see emails from >> people who are. >> >> Of course it there *was* a really good deal on a 5071 … hmmm …. maybe I need >> another Cs …. :) >> >> Bob >> >>> On Feb 3, 2019, at 5:16 PM, Christoph Kopetzky <c...@cksd.de> wrote: >>> >>> Hi Bob, >>> thank you. >>> Wow I did not realize that. Very interesting :) >>> B.t.w. there is a HP 5071A on ...bay item nr 263497171568. Is this cesium >>> clock ok for buying? >>> >>> -- >>> with best Regards >>> >>> Chris >>> >>> Am 03.02.2019 um 21:29 schrieb Bob kb8tq: >>>> Hi >>>> >>>> The key is the top view of the 5065a. You can see through the holes in the >>>> top of the unit. >>>> There’s a big empty space to the right in the picture where the optical >>>> unit / physics package >>>> should be. There also are a few other tidbits missing but the physics >>>> package is the biggie. >>>> >>>> Bob >>>> >>>>> On Feb 3, 2019, at 2:30 PM, Christoph Kopetzky <c...@cksd.de> wrote: >>>>> >>>>> Hello Corby, >>>>> in the case that this is a stupid question... I am sorry but can you tell >>>>> me how I can see that the optical unit is missing? >>>>> There are no pics of an open 5061A device... >>>>> I am also wondering why this seller is shipping these units for this >>>>> extraordinary price. >>>>> He is telling in the description that the shipping costs will be >>>>> calculated at the real destination but I will bet that the click >>>>> on the buy it now button bounds you to pay the whole sum ... >>>>> -- >>>>> >>>>> with best Regards >>>>> >>>>> Chris >>>>> >>>>> Am 03.02.2019 um 18:21 schrieb cdel...@juno.com: >>>>>> Hi, >>>>>> >>>>>> Wanted to warn about the 5065A that has now sold twice on eBay. (Jan 18 >>>>>> and Feb 2) When it first listed I contacted the seller and told him the >>>>>> optical unit was missing (A12) and he should not call it "fully >>>>>> functional" Anyway he sold it for his asking price and now it looks like >>>>>> he just sold it again. If he has it returned and lists it again just be >>>>>> aware its not all there! Not really worth the price with no A12! >>>>>> >>>>>> Cheers, >>>>>> >>>>>> Corby >>>>>> >>>>>> >>>>>> _______________________________________________ >>>>>> time-nuts mailing list -- time-nuts@lists.febo.com >>>>>> To unsubscribe, go to >>>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>>>> and follow the instructions there. >>>>>> >>>>> _______________________________________________ >>>>> time-nuts mailing list -- time-nuts@lists.febo.com >>>>> To unsubscribe, go to >>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>>> and follow the instructions there. >> > _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
