[ntp:questions] almost decided which new PPS GPS to buy

Ron Frazier (NTP) timekeepingntplist at c3energy.com
Mon Mar 5 02:35:23 UTC 2012


On 3/4/2012 6:10 PM, Bruce Lilly wrote:
> On Sun, 04 Mar 2012 22:37:35 +0000, Ron Frazier (NTP) wrote:
>
>    
>>    I
>> want to see what the max performance I can get with USB with handshaking
>> is possible.  I think I can break the + / - 1 ms barrier.
>>      
> See http://gpsd.berlios.de/faq.html#time
>
>    

Hi Bruce,

Thanks for the link.  That's actually out of date since the gpsd folks 
have moved their server.  The new link would be

http://www.catb.org/gpsd/faq.html#time

I read the paragraph you mentioned.  I see that there are substantial 
limitations to USB.  I don't HAVE to have huge accuracy.  Just to get my 
PC clock right to the second, + / - 499 ms would do.  However, I know I 
can get 10's of ms from NTP over internet.  So, psychologically, I want 
to do better than that if I'm using GPS in any form.  Several of my PC's 
don't have serial, so if I happen to have a GPS attached to them, USB is 
my only choice.  I will probably only have it on one PC most of the 
time, but I want each PC to recognize the GPS if I plug it in.  Based on 
the paragraph you mentioned, I think I might be able to achieve + / - 1 
ms over USB with spikes to + / - 2 ms.  If so, that would be fine with 
me.  I just want to push it to the limits and see where those limits 
are.  Thanks for the link to the information.

Sincerely,

Ron


-- 

(PS - If you email me and don't get a quick response, don't be concerned.
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Ron Frazier
timekeepingdude AT c3energy.com



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