[time-nuts] Beaglebone NTP server

Jim Lux jimlux at earthlink.net
Thu Dec 11 11:46:43 EST 2014


On 12/11/14, 8:11 AM, Brian Lloyd wrote:
> Discussing the lifetime of NTP server hardware is all well and good but
> given the thrust of this list, i.e. individual time-nuttery, I don't see it
> as being too germane. Few of us have the same problems that Jim Lux has at
> JPL.
>

Actually, I think my point was that the problems I face at JPL are 
essentially identical to the problems we face at home.  I'm not in the 
time and frequency group (and I don't know that they actually are better 
off.. although they do have rooms full of good clocks), so in our areas, 
we tend to have little point solutions to problems.

It's not like there's a big time/frequency infrastructure with *free* 
spigots from the maser in every lab.  You have to pay for this stuff on 
your project funds, and a lot of times, it seems easier to find a one 
time expense (summer hire intern!) than sign up for a perpetual monthly 
charge plus the infrastructure change cost to pull the fiber/coax.

We do have NTP, of course. But network drops are about $30-40/month, so 
in a lab, you might decide, hey, I can buy a widget for a few hundred 
dollars, and I'll have a better than NTP time source forever. And if 
you've got a student hire, buying that $200 unit off eBay or Amazon and 
taping a GPS antenna to the window starts to look pretty attractive.

There's probably more than a 100 (certainly dozens) of little GPS 
antennas all over the lab connected to a bewildering variety of 
time/frequency sources in labs.  Sure, there's a goodly number of 
TrueTime/Fluke/Pendulum/Symmetricom boxes of various vintages and 
models, but there's also all manner of home-grown stuff.


Those student projects.. What a great way to get someone in for a few 
months on a sort of trial basis.  They get a really nice senior project 
and you both get to find out if JPL is the kind of place they'd like to 
work.  I will confess that the only student intern who I had doing a 
timing related project didn't really become imbued with the true 
fascination for time and time transfer that I was hoping. On the other 
hand, it is truly a niche.. people often don't appreciate how important 
it is, and how widely used it is.)




> I want to have a good time and frequency source in my little network that I
> run. I can put an extra BBB or two aside to run NTP. Eventually I will want
> to replace it but I bet that there will be an adequate SBC and free OS to
> do that when need arises.


Which is exactly what we do at work.. Lots of old PCs doing something, 
but there's that "what do we do when the PC fails" question.  Just like 
at home, you've got a limited budget and time available.  Do you stock a 
couple extra BBBs or RPis? That costs money, and you need to have a 
place to store them where you'll be able to find them.

Or do you hope that when it fails 5 years hence, you'll have time and 
budget to rebuild?

>
> So, I am still looking for a straight-forward, "here is a really good way
> to use a BBB coupled to a GPS 1pps to do NTP," treatise. Better still if
> someone is using their LTE-lite to do it. It seems like a nice little
> package for the amateur time-nut for everyday time and frequency keeping.

Essentially, you want the equivalent of a Microsemi 
(Symmetricom/TrueTime) XL-GPS with the right options for, say, $500 or less.

I do too.

But I'm also not under any illusion that when my homegrown unit fails 
that I'll be able to fix it, or rebuild it for the same price.  It will 
depend on someone having done the redesign using whatever is available 
then, and published the cookbook.


>
> Oh, and if it has nixie tubes to display current time, umso besser! After
> all, I still need to set my old-style watch and a few mechanical
> chronographs I have kicking around.
>




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