[time-nuts] Re: List Opinion/Suggestion(s)

[Bob kb8tq]

Hi

I would strongly suggest that with NTP “more is better”. Three reference devices
is about the minimum. Five is a good target to aim for. Each approach to a device
has its weak points (cost may be one of them). In a “get what you pay for” world,
having a couple of “real” commercial boxes in the mix is a good idea. 

If you have a symmetric delay on your connection to the internet ( delay up and 
delay down are the same) then indeed net based devices can do quite well. It’s a 
rare basement lab that has this sort of connection. Indeed, I know of a number of
companies that have asymmetric connections to the web. 

As with anything “how good do you need?” gets into this. Since this is Time Nuts, 
that can go off the deep end pretty fast. If tens of ms are fine, there are lots of 
answers. Many of them are cheap. If sub milisecond performance is the goal, 
the range of answers is a lot smaller. For sub microsecond, things do get a bit
crazy. 

Even for sub 1 us sort of stuff, the output of a simple GPS module may well be
fine. Give it an antenna with a good sky view so it does not drop out. Get a timing
grade device (or one of the better nav grade parts). Spend your time on writing a
driver that accepts the sawtooth message rather than on other crazy stuff. Since
you are after time rather than frequency, this approach likely is better than a GPSDO.

Fun !!!

Bob

> On Nov 22, 2021, at 1:33 PM, Wilko Bulte <wkb at xs4all.nl> wrote:
> 
> Another option would be a Meinberg NTP appliance. https://www.meinbergglobal.com/
> 
> I have implemented a couple (for geographically dispersed data centres) of the Meinberg LANtime M300 about 10'years back. They still run without a hitch, and have done so without ever failing. "Ours" are dual radio units, GPS and DCF77. They also provide 10MHz, the "quality" of which is determined by which XO you select. See their website. 
> 
> Really well recommended product, German quality ("Gründlichkeit" & "Kwalitätsarbeit")
> 
> Wilko
> (Who also has an M300 in his ham shack, albeit a DCF77-only unit 😀)
> 
>> On 22 Nov 2021, at 19:13, Shawn <comsec at xmtservices.net> wrote:
>> 
>> Hey Guys,
>> 
>> I'd like to ask for opinions from the list if I could.
>> 
>> I have a need to put a couple GPSDOs on some remote locations, 10MHz
>> output plus NTP.  Found some Spectracom 9183s as well as some
>> Symmetricom XLi units on EBay that look like they'd fill the bill.    
>> 
>> The 10MHz will be mostly used by some Service Aggregation Routers to
>> re-clock some DS1s that are being transported over packet microwave and
>> the NTP is for the computers and cameras, the network is closed off
>> from external access.
>> 
>> I'd really appreciate any insights/gotchas/other suggestions that you
>> guys may have in this arena.
>> 
>> Thanks in advance!
>> 
>> Shawn
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