Unless something akin to VLBI or pulsar timing is involved millisecond accuracy will usually suffice for amateur astronomy.
Bruce > On 11 March 2021 at 06:31 Bob kb8tq <kb...@n1k.org> wrote: > > > Hi > > > On Mar 10, 2021, at 12:17 PM, Attila Kinali <att...@kinali.ch> wrote: > > > > On Wed, 10 Mar 2021 06:39:46 -0800 > > "Charlie" <char...@drhabekost.com> wrote: > > > >> My question is thus: It seems that procuring a more precise PPS/time output > >> unit is quite a bit more costly than what I have; even more costly is a > >> unit > >> that has both more precise PPS/time output, > > > > The question is more whether it is good enough. How accurate > > do you need your time? How precise does it need to be? > > If the answer to both questions is smaller than 100ns, > > I suspect that’s a typo. “larger than 100 ns” ( 1 us > 100 ns ….) > would seem to be the correct way to look at it. > > > then you > > are good with anything you can get your hands on, even the cheapest > > GPS receiver. If you need better than that, you need to look > > more closely and calculate each contributor to uncertainty, > > both random and systematic and see where you can and want to > > improve (or compromise). > > > > > >> and a really stable 10 Mhz > >> output ( I might add that I am a Ham, where 1 uhz error is detrimental). > > > > At what time scales you need that 1µHz stability? Is it for > > a few seconds? Or over a few hours? How accurate does it have > > to be? > > And are you sure it is really 1µHz @ 10MHz? Because that's > > a stability better than 1e-13. Which isn't something most people > > just have in their lab. You need a an exceptionally good OCXO to > > reach down there (an OCXO that costs you as much as a car) > > and even those reach it only over a very limited τ between > > about 1s and maybe 100s. Beyond a τ of 1000s you have the option > > of using a HP5065, possibly with Corby's Super-HP6065 modifications. > > Even GPS takes until somwhere like 100ks to reach down to 1e-13. > > Even crazier if you are talking about your transmit frequency at VHF :) :). > Welcome to why Hz, uHz, etc normally are replaced with ppm, ppb, and > the like … That’s been the case in every place I’v ever worked on this stuff. > > Bob > > > > > If you need better than that, either at shorter or longer τ, > > then we are clearly deep in atomic clock territory. Either > > hydrogen maser. caesium beam standard or cold atomic clock. > > > > Attila Kinali > > -- > > The driving force behind research is the question: "Why?" > > There are things we don't understand and things we always > > wonder about. And that's why we do research. > > -- Kobayashi Makoto > > > > _______________________________________________ > > 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.